Cabletron Systems Switch bridges User Manual

Cabletron Systems  
Networking Guide  
Workgroup Solutions  
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Notice  
Notice  
Cabletron Systems reserves the right to make changes in specifications and other information  
contained in this document without prior notice. The reader should in all cases consult Cabletron  
Systems to determine whether any such changes have been made.  
The hardware, firmware, or software described in this manual is subject to change without notice.  
IN NO EVENT SHALL CABLETRON SYSTEMS BE LIABLE FOR ANY INCIDENTAL, INDIRECT,  
SPECIAL, OR CONSEQUENTIAL DAMAGES WHATSOEVER (INCLUDING BUT NOT LIMITED  
TO LOST PROFITS) ARISING OUT OF OR RELATED TO THIS MANUAL OR THE INFORMATION  
CONTAINED IN IT, EVEN IF CABLETRON SYSTEMS HAS BEEN ADVISED OF, KNOWN, OR  
SHOULD HAVE KNOWN, THE POSSIBILITY OF SUCH DAMAGES.  
Copyright 1996 by Cabletron Systems, Inc. All rights reserved.  
Printed in the United States of America.  
Order Number: 9032094 January 1997  
Cabletron Systems, Inc.  
P.O. Box 5005  
Rochester, NH 03866-5005  
Cabletron Systems, SPECTRUM, BRIM, FNB, LANVIEW, Multi Media Access Center, are  
registered trademarks, and Bridge/Router Interface Module, BRIM-A6, BRIM-A6DP, BRIM-E6,  
BRIM-E100, BRIM-F6, BRIM-W6, EPIM, EPIM-A, EPIM-C, EPIM-F1, EPIM-F2, EPIM-F3, EPIM-T,  
EPIM-X, APIM, APIM-11, APIM-21, APIM-22, APIM-29, APIM-67, FPIM, FPIM-00, FPIM-01,  
FPIM-02, FPIM-04, FPIM-05, FPIM-07, TPIM, TPIM-F2, TPIM-F3, TPIM-T1, TPIM-T2, TPIM-T4,  
WPIM, WPIM-T1, WPIM-DDS, WPIM-E1, WPIM-SY, MicroMMAC, MMAC, MMAC-Plus, SEH,  
SEHI, STH, STHI, FN10, FN100, MR9T, MR9T-C, MR9T-E, ESX-1320, ESX-1380, NBR-220, NBR-420,  
NBR-620, SEH100TX, SEHI100-TX, SPECTRUM Element Manager, SPECTRUM for Open Systems,  
are trademarks of Cabletron Systems, Inc.  
All other product names mentioned in this manual may be trademarks or registered trademarks of  
their respective companies.  
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Contents  
Chapter 1  
Introduction  
Using This Guide.........................................................................................................................1-1  
Document Organization .............................................................................................................1-2  
Document Conventions..............................................................................................................1-3  
Warnings and Notifications ................................................................................................1-3  
Formats ..................................................................................................................................1-3  
Additional Assistance .................................................................................................................1-3  
Related Documentation ..............................................................................................................1-4  
Chapter 2  
Review of Networking  
Ethernet.........................................................................................................................................2-2  
Fast Ethernet.................................................................................................................................2-3  
Token Ring....................................................................................................................................2-5  
Chapter 3  
The Workgroup Approach  
Standalones...................................................................................................................................3-1  
Standalones, the Original Networking Devices...............................................................3-2  
Management of Standalones...............................................................................................3-3  
Limitations of Standalones..................................................................................................3-3  
Stackables......................................................................................................................................3-4  
How Stacks Work .................................................................................................................3-5  
Intelligence in the Stack.......................................................................................................3-6  
Internetworking for Stacks..................................................................................................3-6  
Limitations of Stacks............................................................................................................3-7  
Chapter 4  
PIMs and BRIMs  
Port Interface Modules................................................................................................................4-1  
Types of PIMs........................................................................................................................4-2  
Bridge/Router Interface Modules.............................................................................................4-8  
Types of BRIMs .....................................................................................................................4-8  
iii  
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Contents  
Chapter 5  
Network Design  
The Role of the Workgroup ........................................................................................................5-2  
Workgroup Establishment Criteria ....................................................................................5-3  
Selecting Workgroup Technologies....................................................................................5-9  
Creating a Manageable Plan.....................................................................................................5-10  
Logical Layout.....................................................................................................................5-10  
Fault Aversion .....................................................................................................................5-12  
Network Maps and Record Keeping ...............................................................................5-14  
Network Expandability.............................................................................................................5-15  
The Workgroup as the Network ..............................................................................................5-16  
The Workgroup in the Larger Network..................................................................................5-16  
What Is a Backbone?...........................................................................................................5-17  
Methods of Configuring Backbones ................................................................................5-17  
Choosing Backbone Technologies ....................................................................................5-21  
Chapter 6  
Ethernet  
Ethernet Workgroup Devices.....................................................................................................6-2  
Shared Devices......................................................................................................................6-2  
Switched Devices..................................................................................................................6-4  
Ethernet Workgroup Design ......................................................................................................6-5  
The Home Office...................................................................................................................6-5  
The Small Office..................................................................................................................6-11  
The Remote Office ..............................................................................................................6-16  
The High-End Department ...............................................................................................6-19  
Permutations .......................................................................................................................6-24  
Chapter 7  
Fast Ethernet  
Fast Ethernet Workgroup Devices.............................................................................................7-1  
Shared Devices......................................................................................................................7-1  
Switched Devices..................................................................................................................7-2  
Fast Ethernet Workgroup Design ..............................................................................................7-3  
Small Offices..........................................................................................................................7-3  
High-End Department .........................................................................................................7-6  
Fast Ethernet as a Backbone................................................................................................7-9  
Chapter 8  
Token Ring  
Token Ring Workgroup Devices................................................................................................8-1  
Shared Devices......................................................................................................................8-1  
Token Ring Workgroup Design .................................................................................................8-3  
Small Office............................................................................................................................8-3  
iv  
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Contents  
Appendix A Charts and Tables  
Workgroup Design Tables .........................................................................................................A-1  
Ethernet.................................................................................................................................A-1  
Fast Ethernet.........................................................................................................................A-3  
Token Ring............................................................................................................................A-4  
PIMs and BRIMs..................................................................................................................A-5  
Networking Standards and Limitations..................................................................................A-8  
Ethernet.................................................................................................................................A-8  
Fast Ethernet.........................................................................................................................A-9  
Token Ring..........................................................................................................................A-10  
FDDI ....................................................................................................................................A-12  
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Contents  
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Chapter 1  
Introduction  
Using This Guide  
The Cabletron Systems Networking Guide - Workgroup Solutions is intended  
to provide much of the information necessary to allow Network Managers to  
design and evaluate workgroup networks using the Cabletron Systems family of  
standalone and stackable networking products. This guide also provides the  
methods for associating these workgroups into larger networks or incorporating  
them into existing facility networks.  
This document was written with the assumption that the reader has some  
familiarity with four networking technologies; Ethernet, Fast Ethernet, Token  
Ring, and FDDI. If you are unfamiliar with these technologies, Cabletron Systems  
produces instructional and reference materials that may be of assistance in  
learning these networking technologies. The available instructional materials are  
referred to in Related Documentation, later in this chapter. For those already  
familiar with the Ethernet, Fast Ethernet, and Token Ring technologies, a brief  
refresher in the main design-specific aspects of these technologies is provided in  
later chapters.  
This document assumes that the reader has read the Cabletron  
Systems Networking Guide - MMAC-FNB Solutions. The  
NOTE  
document is available on the Cabletron Systems Hardware  
Manuals CD-ROM. If you are unable to locate a copy of that  
document, you may also order a printed version of any  
document listed above from Cabletron Systems.  
1-1  
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Introduction  
Document Organization  
The following summarizes the organization of this manual:  
Chapter 1, Introduction, provides basic information about this document,  
including the organization and format of the document.  
Chapter 2, Review of Networking, describes the important design restrictions  
and characteristics of three basic networking technologies.  
Chapter 3, The Workgroup Approach, explains the history and product  
philosophy behind standalone and stackable workgroup networking devices.  
Chapter 4, PIMs and BRIMs, details the operation and use of Cabletron Systems’  
various speciality interface modules.  
Chapter 5, Network Design, covers the information and decisions involved in the  
identification of networking needs and formation of solutions which meet those  
needs.  
Chapter 6, Ethernet, explains and illustrates the network design process involved  
in creating Ethernet workgroups.  
Chapter 7, Fast Ethernet, provides information and examples that show the  
design issues that must be dealt with when configuring a Fast Ethernet network.  
Chapter 8, Token Ring, supplies design and configuration information for Token  
Ring workgroup solutions.  
Appendix A, Charts and Tables, provides a centralized source for the design  
tables found throughout this document, and useful information relating to the  
networking technologies that are discussed.  
1-2  
Document Organization  
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Introduction  
Document Conventions  
Warnings and Notifications  
Note symbol. Calls the reader’s attention to any item of  
information that may be of special importance.  
NOTE  
Formats  
References to chapters or sections within this document are printed in boldface  
type.  
References to other Cabletron Systems publications or documents are printed in  
italic type.  
Additional Assistance  
The design of a network is a complex and highly specialized process. Due to the  
different nature of each and every cabling installation and the special problems  
and concerns raised by any facility, there may be aspects of network design that  
are not covered in this guide.  
If you have doubts about your network design, or if you require installation  
personnel to perform the actual installation of hardware and cabling, Cabletron  
Systems maintains a staff of network design personnel and highly-trained cabling  
and hardware installation technicians. The services of the Networking Services  
group are available to customers at any time. If you are interested in obtaining  
design assistance or a network installation plan from the Networking Services  
group, contact your Cabletron Systems Sales Representative.  
In addition to the availability of Networking Services, the Cabletron Systems  
Technical Support department is available to answer customer questions  
regarding existing Cabletron Systems networks or planned expansion issues.  
Contact Cabletron Systems at (603) 332-9400 to reach the Technical Support  
department with any specific product-related questions you may have.  
Document Conventions  
1-3  
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Introduction  
Related Documentation  
The following publications may be of assistance to you in the design process.  
Several of these documents present information supplied in this guide in greater  
or lesser detail than they are presented here.  
Cabletron Systems Networking Guide - MMAC-FNB Solutions  
Cabletron Systems Cabling Guide  
Cabletron Systems Ethernet Technology Guide  
Cabletron Systems Token Ring Technology Guide  
Cabletron Systems FDDI Technology Guide  
For additional product or other information, visit us at  
http://www.cabletron.com or contact Cabletron Systems by phone at  
(603) 332-9400.  
1-4  
Related Documentation  
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Chapter 2  
Review of Networking  
This chapter discusses the defining characteristics of three major Local Area Network (LAN)  
technologies.  
Before discussing the selection of networking hardware for workgroup design, an  
understanding of the major standardized networking technologies available for  
these designs is necessary. This chapter provides a brief review of the three major  
networking technologies that are to be treated in this document: Ethernet, Fast  
Ethernet, and Token Ring.  
This section is intended to be a review of the most important aspects of these  
technologies, and is not expected to stand alone. For more detailed information,  
Cabletron Systems publishes a series of other documents that treat these  
technologies in greater detail. For introductory information, the Cabletron Systems  
Networking Guide - MMAC-FNB Solutions manual provides extensive training  
information in the basics of these technologies. Further technical detail is  
available in the Cabletron Systems Technology Overview Guides. A list of associated  
publications, including these titles, is supplied in the Related Documentation  
section of Chapter 1.  
2-1  
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Review of Networking  
Ethernet  
Ethernet is a local area networking technology that was initially developed in the  
1970s by the Xerox Corporation. It is based on the principles of workstations  
being responsible for their own transmissions and operation. It is sometimes  
referred to as 802.3 networking, in reference to the number of the IEEE standards  
body which subsumes all Ethernet operations.  
Ethernet networks provide an operating bandwidth of 10 megabits per second  
(Mbps). Bandwidth is a networking term which describes the operating speed of a  
technology. In the case of Ethernet, a perfectly operating, theoretical Ethernet  
network, can move 10,000,000 bits of data each second between two stations on  
the network.  
Ethernet is a Carrier Sense Multiple Access/Collision Detection (CSMA/CD)  
LAN technology. Stations on an Ethernet LAN can access the network at any time.  
Before sending data, Ethernet stations “listen” to the network to see if it is already  
in use. If so, the station wishing to transmit waits and examines the network again  
later. If the network is not in use, the station transmits. A collision occurs when  
two stations listen for network traffic, “hear” none, then transmit simultaneously.  
In this case, both transmissions are damaged and the stations, sensing this  
collision, must retransmit at some later time. Backoff algorithms determine when  
the colliding stations retransmit.  
Ethernet is a broadcast network. In other words, all stations see all frames  
(collections of data), regardless of if they are an intended destination. Each station  
must examine received frames to determine if it is the destination. If so, the frame  
is passed to a higher protocol layer for appropriate processing.  
Ethernet transmits data frames over a physical medium of coaxial, fiber optic, or  
twisted pair cable. The coaxial and fiber optic cable typically represents the  
backbone of an Ethernet LAN, while twisted pair is used as a low cost connection  
from the backbone to the desktop.  
Ethernet LANs have the following media restrictions in order to adhere to IEEE  
802.3 standards:  
Bus Length: The maximum bus length for an Ethernet LAN for all media types  
are as follows:  
-
-
-
500 m for 10BASE5 coaxial cable  
185 m for 10BASE2 coaxial cable  
2,000 m for multi mode fiber optic (10BASE-F) cable  
(5,000 m for single mode)  
-
100 m for twisted pair (10BASE-T) cable.  
These media lengths are not precise values. Actual maximum  
cable lengths are strongly dependent on the physical cable  
characteristics.  
NOTE  
2-2  
Ethernet  
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Review of Networking  
AUI Length: The maximum Attachment Unit Interface (AUI) cable length is  
50 m for connections from a transceiver to an Ethernet device. The 50 m  
distance is the allowable maximum for standard AUI, while a maximum  
length of 16.5 m has been set for office AUI.  
Number of Stations per Network: IEEE standards specify that the maximum  
allowable number of stations per un-bridged network is 1,024, regardless of  
media type. The 10BASE5 networks are allowed 100 taps per segment, while  
10BASE2 networks are allowed 30 taps per segment with a maximum of  
64 devices per tap each. (Fiber optic and twisted pair cable are point-to-point  
media which do not allow taps or branches).  
If it becomes necessary to extend the network beyond the IEEE  
limit of 1,024 devices, a bridge can be used to connect another  
full specification Ethernet network.  
NOTE  
Maximum Signal Path: The maximum allowable signal path is 4 repeaters, 5  
segments (with at least 2 segments being unpopulated Inter-Repeater Links),  
and 7 bridges for all media types.  
There are other limitations involved in the IEEE 802.3 standard and the various  
cable specifications, which are more detailed and complex. These limitations are  
covered in detail in the Cabletron Systems Cabling Guide and the Cabletron Systems  
Ethernet Technology Overview.  
Fast Ethernet  
Fast Ethernet is a networking technology that grew out of the popular Ethernet  
technology described above. Fast Ethernet uses the same CSMA/CD media  
access method and basic network operation. The main differences between  
Ethernet and Fast Ethernet are the available bandwidth and media limitations.  
Fast Ethernet increases the available bandwidth of a single network to 100 Mbps,  
ten times faster than normal Ethernet. This increase in transmission speed,  
however, comes at a cost to the flexibility of the network. By increasing the speed  
of transmission by a factor of 10, the required characteristics of Ethernet links  
were likewise reduced.  
Fast Ethernet networks only support UTP and multimode fiber optics as standard  
transmission media. The two standards for these media are 100BASE-TX for  
Category 5 UTP, and 100BASE-FX for multimode fiber optics.  
The IEEE 802.3u standard defines two different types of Fast Ethernet repeaters:  
Classes I and II. All Cabletron Systems Fast Ethernet products discussed in this  
document are Class I repeaters. A Fast Ethernet network designed with Class I  
repeaters allows a signal path from one station, through a Fast Ethernet link, to a  
Class I repeater, through another Fast Ethernet link, to a receiving station. No  
other Class I repeaters may be placed in this signal path.  
Fast Ethernet  
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Review of Networking  
This signal path, two end stations and the repeaters between them, is called the  
network radius. Unlike standard Ethernet networks, Fast Ethernet networks have  
a maximum network radius that may restrict the lengths of station cabling to less  
than the maximum allowable distances for single links. Typically, network radius  
calculations are only important when mixing 100BASE-TX and 100BASE-FX  
networks. The maximum network radius limits are provided later in this section.  
As the imposition of a maximum network radius on mixed 100BASE-TX and  
100BASE-FX networks severely limits the design options of Fast Ethernet  
networks, Fast Ethernet devices may incorporate buffered uplinks. A buffered  
uplink is a Fast Ethernet port on a repeater which allows the repeater to ignore the  
collision domain of the uplink. This allows the buffered uplink to be a  
maximum-length segment even in mixed media environments.  
A buffered uplink is considered a bridged or switched  
connection only for purposes of determining cable length.  
NOTE  
Fast Ethernet LANs must meet the following media and network restrictions in  
order to adhere to IEEE standards:  
Cabling Quality: All 100BASE-TX links require UTP cabling meeting or  
exceeding the Telecommunications Industry Association (TIA) Category 5  
specification. The link must be compliant from end to end, including all  
connectors and patch panels.  
Link Length: No single link in the Fast Ethernet network may exceed the  
limitations given below, including jumper cables and patch cables:  
-
-
100 m for 100BASE-TX networks  
400 m for 100BASE-FX networks  
Network Radius: Network radius is the distance traveled from the station with  
the longest media link to the Fast Ethernet repeater and out to the station with  
the second-longest media link. In order to meet IEEE standards, Fast Ethernet  
networks constructed with Class I repeaters must not exceed the following  
maximum network radii:  
-
-
-
200 m for homogenous 100BASE-TX networks  
260 m for mixed 100BASE-TX and 100BASE-FX networks  
272 m for homogenous 100BASE-FX networks  
These media lengths are fixed values. Deviation from these  
maximums will lead to poor network performance.  
NOTE  
2-4  
Fast Ethernet  
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Review of Networking  
Fast Ethernet networks designed using Class II repeaters may not exceed the  
following maximum network radii:  
-
-
200 m for homogenous 100BASE-TX networks  
320 m for homogenous 100BASE-FX networks  
Buffered Uplinks: If a buffered uplink is used to make a connection, the  
allowable length of the buffered uplink itself does not change, but the  
maximum network radius calculations will change. Assuming that the  
buffered uplink is the longest link in the repeater radius, the maximum  
allowable network radius will change to the values given below:  
-
-
500 m for mixed 100BASE-TX and buffered 100BASE-FX uplink  
800 m for homogenous 100BASE-FX networks  
Number of Stations per Network: IEEE standards specify that the maximum  
allowable number of stations per single-segment network is 1,024, regardless  
of media type.  
If it becomes necessary to extend the network beyond the IEEE  
limit of 1,024 devices, a bridge or switch can be used to  
connect another full specification Fast Ethernet network.  
NOTE  
Maximum Signal Path: The maximum allowable signal path for a Fast  
Ethernet network is one Class I repeater, two segments for all media types. The  
use of bridges, switches, or routers can allow the creation of larger networks.  
Token Ring  
Token Ring network operation is based on the principle that the operation of the  
entire network determines when a station may transmit and when it will receive.  
Stations monitor one another, and one station acts as an overall ring monitor,  
keeping track of important statistics. Token Ring stations are connected to one  
another in a predetermined order, and network frames pass from one station to  
the next, following that order. A specialized network frame, called a token, is  
passed around the ring at regular intervals. The transmission of the token helps  
establish some of the operational statistics for the network, and receiving it allows  
a station to transmit.  
The Token Ring technology is designed to operate at either of two speeds: 4 Mbps  
or 16 Mbps. This speed selection is made when the network is installed, and the  
speed must apply equally to all stations (you may not split a ring into groups of  
16 Mbps and 4 Mbps stations).  
Token Ring  
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Review of Networking  
The transmission and reception of the token determines the amount of time that  
any station will have to transmit data during its turn, offering a measure of  
predictability not available in Ethernet or Fast Ethernet. This predictability also  
allows Token Ring networks to incorporate special error-detection and correction  
functions which can locate and correct network problems without human  
intervention.  
The predictability of the Token Ring technology also leads to a number of  
limitations on the number of stations that can be connected to a network and the  
maximum cable lengths that a signal may be passed across. Since the stations are  
configured to expect reception of the token at certain increments of time,  
exceeding the maximum number of stations or the maximum length of cabling  
between stations can delay the token’s progress, causing the Token Ring network  
to suffer errors and poor performance.  
In order to stretch the capabilities of a Token Ring network, various technologies  
are available which extend the distance a signal can travel before suffering  
degradation or loss of signal timing due to cable lengths or high station count.  
One method of increasing the resilience of a Token Ring network is the  
incorporation of what is called “active circuitry.Token Ring station ports with  
this active circuitry regenerate, strengthen, and re-time any Token Ring signal  
received by or transmitted from that interface.  
All Cabletron Systems stackable and standalone Token Ring  
products incorporate active circuitry on all ports.  
NOTE  
Token Ring devices can also extend the distance that a ring can cover through the  
use of Ring-In/Ring-Out, or RI/RO cables. RI/RO cables are designed only to  
make connections between Token Ring concentrator devices, and extend the area  
that a ring can support by allowing long-distance links to other Token Ring  
devices.  
RI/RO connections are not bridge or switch interfaces. They do  
not create a new Token Ring network.  
NOTE  
2-6  
Token Ring  
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Review of Networking  
Token Ring networks can use a variety of physical cabling, including Unshielded  
Twisted Pair (UTP), Shielded Twisted Pair (STP), or fiber optic cabling. The  
characteristics of the various cables can directly impact the operational limitations  
of a Token Ring network which uses a particular media.  
Lobe Cable Lengths for 4 Mbps Token Rings: The operation of a 4 Mbps Token  
Ring network imposes some relatively generous limitations on the maximum  
length of any station cable (also called a lobe cable) connected to an active port  
in the network as shown in the following list:  
-
-
-
-
-
-
IBM Types 1, 2 STP: 300 m  
IBM Types 6, 9 STP: 200 m  
Category 5 UTP: 250 m  
Categories 3, 4 UTP: 200 m  
Multimode Fiber Optics: 2000 m  
Single Mode Fiber Optics: 2000 m  
Lobe Cable Lengths for 16 Mbps Token Rings: 16 Mbps Token Ring networks  
also impose limitations on the maximum length of any media connected to an  
active port as shown in the following list:  
-
-
-
-
-
-
IBM Types 1, 2 STP: 150 m  
IBM Types 6, 9 STP: 100 m  
Category 5 UTP: 120 m  
Categories 3, 4 UTP: 100 m  
Multimode Fiber Optics: 2000 m  
Single Mode Fiber Optics: 2000 m  
RI/RO Cable Lengths for 4 Mbps Token Rings: 4 Mbps Token Ring networks  
also require that Ring-In/Ring-Out (RI/RO) connections be no longer than a  
certain amount. This amount is dependent upon the media being used for the  
RI/RO connection as shown in the following list:  
-
-
-
-
-
IBM Types 1, 2 STP: 770 m  
Category 5 UTP: 250 m  
Categories 3, 4 UTP: 200 m  
Multimode Fiber Optics: 2000 m  
Single Mode Fiber Optics: 2000 m  
RI/RO Cable Lengths for 16 Mbps Token Rings: 16 Mbps Token Ring networks  
also require that Ring-In/Ring-Out (RI/RO) connections not exceed the  
lengths given below:  
-
-
-
-
-
IBM Types 1, 2 STP: 346 m  
Category 5 UTP: 120 m  
Categories 3, 4 UTP: 100 m  
Multimode Fiber Optics: 2000 m  
Single Mode Fiber Optics: 2000 m  
Token Ring  
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Review of Networking  
Number of Stations Per 4 Mbps Token Ring: In the same fashion as the limits  
imposed on cable lengths due to the operating speed of the network and type  
of cabling used, there are limitations on the number of stations that may be  
connected to a single ring using active circuitry. If these numbers are exceeded,  
a bridge, switch, or other segmentation device must be used to break the ring  
into two or more smaller rings as detailed in the list below:  
-
-
-
-
-
-
IBM Types 1, 2 STP: 250 stations  
IBM Types 6, 9 STP: 250 stations  
Category 5 UTP: 150 stations  
Categories 3, 4 UTP: 150 stations  
Multimode Fiber Optics: 250 stations  
Single Mode Fiber Optics: 250 stations  
Number of Stations Per 16 Mbps Token Ring: The limitation on the number of  
stations in the Token Ring also applies to 16 Mbps networks. In one case, the  
number of stations supported by these faster Token Ring networks is  
significantly lower than the number supported by the 4 Mbps rings.  
-
-
-
-
-
-
IBM Types 1, 2 STP: 250 stations  
IBM Types 6, 9 STP: 136 stations  
Category 5 UTP: 150 stations  
Categories 3, 4 UTP: 150 stations  
Multimode Fiber Optics: 250 stations  
Single Mode Fiber Optics: 250 stations  
The Token Ring limitations that are described above are summarized for your  
ease of reference in Table 2-1. This table is also repeated in Appendix A, Charts  
and Tables.  
Table 2-1. Token Ring Maximums  
Max Lobe Cable  
Max # of Stations  
Cable  
Type  
Length  
Media  
4 Mbps  
16 Mbps  
4 Mbps  
16 Mbps  
STP  
IBM Types 1, 2  
IBM Types 6, 9  
Category 5  
250  
250  
150  
150  
250  
250  
250  
136  
150  
150  
250  
250  
300 m  
200 m  
250 m  
200 m  
2000 m  
2000 m  
150 m  
100 m  
120 m  
100 m  
2000 m  
2000 m  
a
UTP  
Categories 3, 4  
Multimode  
Fiber Optics  
Single Mode  
a. IBM Type 6 cable is recommended for use as jumper cabling only and should not be used for  
facility cabling installations.  
2-8  
Token Ring  
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Review of Networking  
There are other limitations involved in the IEEE 802.5 standard and the various  
cable specifications that are more detailed and complex. These limitations are  
covered in detail in the Cabletron Systems Cabling Guide and the Cabletron Systems  
Token Ring Technology Overview.  
Token Ring  
2-9  
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Review of Networking  
2-10  
Token Ring  
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Chapter 3  
The Workgroup Approach  
This chapter describes the basic operation and design of stackable and standalone devices and the  
methods used to meet common networking needs with these devices.  
Standalone and stackable networking devices are specialized and important parts  
of any end-to-end network design strategy. Understanding the design philosophy  
and product evolution of these products can greatly aid a Network Designer in  
determining where, and to what extent to implement standalone and stackable  
devices in a new or existing network.  
Standalones  
A standalone device is one which, as the name implies, “stands alone” in the  
network. A standalone device does not rely on any other network device to  
operate, nor does it provide for the operation of other devices itself. This is a  
distinct difference from networking devices such as modular networking chassis,  
which require combinations of discrete modules be plugged into them for their  
own operation.  
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The Workgroup Approach  
Standalones, the Original Networking Devices  
Standalone devices are the second oldest devices in Local Area Networking,  
having been developed shortly after transceivers. The basic and most  
straightforward standalone device is the repeater or concentrator, a device that  
allows a network signal received on one interface, or port, to be strengthened,  
repeater, receiving a weak signal and transmitting a cleaner, stronger signal.  
incoming signal  
outgoing signal  
repeater  
2094n01  
Figure 3-1. Repeater Operation  
These simple, inexpensive devices were designed to expand the limitations and  
capabilities of early networks, allowing them to grow beyond the limitations  
imposed by the cabling they were based upon. As time went on, and networks  
grew in size, the standalone devices began to offer greater control and  
expandability. The design of multiport repeaters allowed one signal to be sent out  
several interfaces simultaneously, and the standalone bridge offered the ability to  
localize network traffic for security and improved performance.  
The other most common standalone device in early networks was the standalone  
bridge. The standalone bridge was commonly a two-port device which performed  
segmentation functions between two networks. The multiport bridge was  
eventually followed up by the multiport switch, which made switched  
connections between several network interfaces.  
The use of these standalone devices allowed simple networks to expand beyond  
the limits of the cabling and the physical constraints of the technologies being  
used. The standalone networking devices were relatively simple, however, and  
did not always support the numbers of users that facilities contained.  
3-2  
Standalones  
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The Workgroup Approach  
Management of Standalones  
As standalone devices became more complex, the need to control them became  
greater. The need to have some form of troubleshooting and control process in  
place for an eight-port repeater is minimal. In a repeated network where more  
than 200 users are connected to a single repeater, management capabilities are no  
longer luxuries, they are a necessity. The advent of standalone bridges, which  
required software configuration and monitoring, marked the introduction of  
management capabilities to the standalone devices.  
While the most basic standalone devices were unable to support any management  
and control operations, networking hardware vendors such as Cabletron Systems  
began to incorporate management functions into their devices, making intelligent  
networking devices. The growth of networks and the control offered by these  
intelligent devices paved the way for the modular networking chassis, or hub.  
Standalones could handle the growing size of networks, but not always the  
growing complexity. The modular chassis allowed facility networks to support far  
greater numbers of users from a single location than was possible with standalone  
devices.  
Limitations of Standalones  
In time, the networking market broke into facilities that were small enough to use  
standalone networking devices and facilities that required the control and  
flexibility of the modular hub. As this trend continued, a gap widened between  
the low-cost, low-flexibility standalone devices and the more expensive, more  
flexible modular chassis. Facilities that had opted to use standalone devices were  
painting themselves into a corner. The standalone devices had no option for  
adding more users other than expanding the network. There were no options  
available for adding new networking technologies to the standalone devices, and  
any upgrade to the capabilities of the network would involve a costly,  
all-or-nothing replacement of all equipment.  
At the same time, the limitations that nobody thought they would reach became  
very real threats to the continued growth of networks reliant on standalones. That  
old repeater rule, which Network Managers had been able to get around with  
clever tricks of physical layout, was looming on the horizon, and user counts  
continued to climb.  
Standalones  
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The Workgroup Approach  
Stackables  
To cope with the limited flexibility and expandability of standalones, the  
stackable hub, or stackable, was developed. The stackable design allowed a series  
of devices to act as a single device. With a stackable hub system, five separate  
devices could act as a single device. From the point of view of network design,  
this was a master stroke. A single stack, which operated as one big device, could  
support as many users as four or five standalone repeaters. To the network, the  
physical organization  
logical organization  
2094n02  
Figure 3-2. Physical and Logical Views of Stackables  
The stackable has a smaller network footprint than an equivalent number of  
standalone devices. In effect, the stack fools the network into thinking that the  
users connected to the stack are in a single repeater or concentrator.  
By placing stackables together in a collection called a stack, the available options  
for user connections at individual workgroup locations grew dramatically. Also,  
the ability to simply add stackables to the stack in order to accommodate new  
users gave some measure of an upgrade path to users of stackable devices.  
Stackable hubs of different technologies cannot be mixed. Each  
stack must use a single networking technology. For example,  
NOTE  
you cannot combine Ethernet and Fast Ethernet stackables in a  
single stack.  
Stackables, being less expensive than modular hubs and more flexible and  
expandable than standalones, helped to fill in the chasm between the high-end  
and low-end network strategies.  
3-4  
Stackables  
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The Workgroup Approach  
How Stacks Work  
Stackable hubs communicate with one another through proprietary  
interconnection cables. The cables used in Cabletron Systems’ stackable hub  
solution are called HubSTACK Interconnect Cables. In Ethernet stackable  
environments, these cables are short, multistrand cables with special, D-shaped  
connectors that attach to ports on the backs of the stackable hubs, as shown in  
Figure 3-3. In Token Ring stackable solutions, the interconnect cables are short  
twisted pair segments that connect each stackable unit directly to the base unit.  
REAR VIEW  
SEHI Managing 4 SEH Non-Intelligent Hubs  
SEH100TX-22 100BASE-TX HUB WITH LANVIEW®  
OUT  
SEH100TX INTERCONNECT  
IN  
SEH100TX-22 100BASE-TX HUB WITH LANVIEW®  
SEH100TX-22 100BASE-TX HUB WITH LANVIEW®  
SEH100TX-22 100BASE-TX HUB WITH LANVIEW®  
SEHI100TX-22 100BASE-TX HUB WITH LANVIEW®  
OUT  
SEH100TX INTERCONNECT  
IN  
HubSTACK  
Interconnect Cable  
OUT  
SEH100TX INTERCONNECT  
IN  
OUT  
SEH100TX INTERCONNECT  
IN  
OUT  
SEHI100TX INTERCONNECT  
IN  
2094n03  
Figure 3-3. HubSTACK Interconnect Cables  
The HubSTACK cables handle the communications between stackable devices,  
including network traffic and management communications. The use of these  
custom, short cables allows the stack to act as a single repeater or concentrator. In  
essence, the cables and connectors used to chain the stackable hubs together  
mimic the operation of the backplane of a modular hub.  
Stackables  
3-5  
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The Workgroup Approach  
HubSTACK Interconnect Cables are connected in a particular sequence, from the  
OUT port of the first device in the stack to the IN port of the next. This  
arrangement is repeated from device to device as more stackable hubs are  
If it becomes necessary to disconnect a HubSTACK  
Interconnect Cable from a device in the stack, disconnect the  
NOTE  
cable at the OUT port of the previous device in the stack to  
ensure proper termination of the Interconnect Cable chain.  
Intelligence in the Stack  
Once stackables became accepted in networks, users demanded management for  
them. The response from manufacturers was to make intelligent stackable  
devices. The design of intelligence and management capabilities for the stackable  
devices followed a path similar to the incorporation of management into modular  
chassis. Rather than requiring that all the stackables in a stack be intelligent in  
order for management functions to be performed, stackable intelligence is  
contained in only one device and is extended to the non-intelligent devices in the  
stack. Thus, only one intelligent device is needed to manage a full stack, keeping  
the costs of management down.  
The basis of the intelligent stack is that the first device in each stack is the only one  
that requires this management intelligence. This intelligent stackable, or base,  
provides management services for the rest of the devices in its stack over the same  
connection that is used for stackable to stackable communications. The  
management traffic moves across the artificial backplane that is set up through  
the interconnect cables.  
Internetworking for Stacks  
As stackable devices and stacks are easy to design and configure, and often have a  
lower cost than modular networking chassis for these small-scale, simplistic  
network implementations, they are often found in large enterprise networks  
acting as fringe devices. These devices operate at the frontier areas of the network,  
where users connect to small shared network segments.  
The use of stackable devices in these frontier workgroup environments often  
necessitates the use of a differing network technology, such as Fiber Distributed  
Data Interface (FDDI) or Asynchronous Transfer Mode (ATM) to make  
high-bandwidth connections to the enterprise network backbone or a central  
campus switch. The basic design of stackable hubs does not allow for the  
incorporation of different network technologies as does a modular networking  
chassis such as the Cabletron Systems Multi-Media Access Center, or MMAC.  
3-6  
Stackables  
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The Workgroup Approach  
Initially, Network Designers wishing to make connections from stacks to  
backbone technologies would be forced to add an additional standalone device to  
the network at the workgroup area. The addition of a standalone switch, bridge,  
or router that supported the technology of the stack and the technology of the  
backbone would allow for the interconnection, or internetworking, of the stack  
and the backbone.  
To assist Network Designers in creating a flexible and elegant solution to the  
problem of internetworking for stacks, and to reduce the number of separate  
devices that had to be shepherded at any facility, Cabletron Systems introduced  
Bridge/Router Interface Module (BRIM) technology to the stackable and  
standalone product line.  
The BRIM is a specialized module that can be added to any BRIM-capable  
Cabletron Systems device. The BRIM provides two interfaces: one to the internal  
network segment of the device that it is placed in, and one to an external network.  
Several BRIMs are available to support a wide variety of networking  
technologies. The available BRIMs and their configuration options are detailed in  
Chapter 4, PIMs and BRIMs.  
By incorporating the BRIM technology into a number of standalone and stackable  
devices, Cabletron Systems makes it easy to use stackable hubs and standalone  
switches as frontier devices for an enterprise network, or as a small workgroup  
solution at any location. The availability of Wide Area Network (WAN)  
technology BRIMs also makes the BRIM-capable stackable devices ideal choices  
for branch office scenarios.  
Limitations of Stacks  
While stackables are very well suited to a number of network implementations,  
they have their limitations. As stackables were developed to fill the gap between  
standalone devices and modular chassis, some networking capabilities are better  
handled by modular hubs.  
Modular chassis allow for the mixing of multiple technologies in a single location  
much more readily than stackables. If a network implementation requires 43  
Ethernet users, 11 Token Ring users, and four FDDI stations, a single modular  
chassis will support these requirements, while a series of stackable and  
standalone devices would have to be purchased, installed, and maintained to  
accommodate the same need.  
Stackables  
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The Workgroup Approach  
In addition, stackable and standalone devices are typically available for only the  
most common of networking media: UTP and STP. In situations where several  
users connect to the network with UTP, a few make their connections with fiber  
optics, and there is a handful of existing coaxial cable segments, a solution using  
stackables would have to provide a series of external transceivers at each location.  
While not extremely expensive, these external transceivers can become  
maintenance and design hurdles when troubleshooting or expanding the  
network. Modules for modular chassis, with support for a wider variety of  
networking media, are more able to accommodate different existing and future  
needs.  
The design of a modular chassis also allows for the segmentation and  
interconnection of networks within a single chassis, the incorporation of power  
redundancy and added fault-tolerance, and a longer path of growth and  
expansion, both to add new users and incorporate new technologies.  
3-8  
Stackables  
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Chapter 4  
PIMs and BRIMs  
This chapter deals with the special methods of connecting standalone and stackable devices to one  
another regardless of cabling media or networking technology.  
While many network design implementations are simple and straightforward,  
there are several that must incorporate complexity beyond a single segment,  
media type, or even a single networking technology. These complex networks are  
quite frequently the domain of modular networking chassis, such as the  
Cabletron Systems MMAC-FNB series of hubs, or the enterprise network switch  
platform, such as the Cabletron Systems MMAC-Plus. It is important that  
workgroup devices be able to support complexity, so Cabletron Systems has  
designed support for different media, segmentation, and internetworking needs  
into several of its workgroup solutions devices.  
Port Interface Modules  
In order to support a wider variety of networking needs, Cabletron Systems  
incorporated specialized, user-configurable ports on many of its standalone and  
stackable devices. These ports, called Port Interface Module slots, or PIM slots, are  
available openings in devices into which a PIM can be placed. These PIMs can be  
constructed to provide connectivity for any standardized networking technology  
and most port types.  
Device  
PIM  
2094n04  
Figure 4-1. PIM Configuration  
4-1  
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PIMs and BRIMs  
The PIMs can be added at any time, allowing a Network Manager to add  
capabilities for special links at any time. Originally developed for use in the  
Cabletron Systems Media Interface Module (MIM) line for the MMAC-FNB  
modular chassis, the PIMs allow a device to support an additional type of cabling  
in addition to its primary cabling type. A device which was built to provide 24  
RJ45 ports for connections to UTP cabling can also support a single multimode  
fiber optic connection with the addition of a PIM that supports multimode fiber  
optics.  
In essence, the PIMs act as internal transceivers. The internalization of the PIMs  
provides specific benefits over external transceivers. The internalized PIM does  
not need a metal or plastic case, requires no dedicated power supply, does not  
require jumper cabling, and, most important from a design point of view, only  
counts as one transceiver in a network link.  
As a reminder: an Ethernet network may not contain any path  
where a signal passes through more than three transceivers  
NOTE  
before reaching its destination or passing through a bridge,  
switch, or repeater.  
Types of PIMs  
To provide connectivity options for the widest variety of networking needs, and  
to increase the flexibility of Cabletron Systems networking devices, there are  
several types of PIMs available. These different PIMs are designated by a prefix  
and a suffix. A table detailing all the currently released PIMs and the special  
characteristics of them may be found at the end of this section.  
(E)thernet  
(F)iber Optics  
EPIM-F2  
Type 2  
(ST Connectors)  
2094n05  
Figure 4-2. PIM Decoding  
The prefix of the PIM’s name (in this case “E”) identifies what networking  
technology the PIM is designed for use with. Most often this prefix is the first  
letter of that technology’s name (E for Ethernet, T for Token Ring, etc.). PIMs may  
only be used in devices of the correct networking technology. You may not, for  
example, place an Ethernet PIM in a Token Ring device. The PIM will not operate,  
and may, in fact, disrupt the operation of the Token Ring network.  
4-2  
Port Interface Modules  
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PIMs and BRIMs  
The suffix of the PIM’s product name, which follows the hyphen, specifies what  
media type and connector style the PIM provides. Typically any alphabetic  
characters indicate the media, while numerical characters indicate a special  
indicated that the PIM is for fiber optic media, while the “2” further indicates that  
the PIM provides Straight-Tip, or ST-type connectors.  
EPIMs  
EPIMs are Ethernet Port Interface Modules. An EPIM provides one shared or  
switched Ethernet connection to a single type of Ethernet media. EPIMs are  
typically used to make connections from workgroups to enterprise switches, data  
centers, or specialized equipment. The EPIMs that are available from Cabletron  
Systems and the types of cabling and connectors supported by each are listed  
below:  
EPIM-A:  
EPIM-C:  
EPIM-F1:  
EPIM-F2:  
EPIM-F3:  
EPIM-T:  
EPIM-X:  
AUI (DB15 Female Connector)  
Coaxial Cable (RG-58 Connector)  
Multimode Fiber Optics (SMA Connectors)  
Multimode Fiber Optics (ST Connectors)  
Single Mode Fiber Optics (ST Connectors)  
Shielded or Unshielded Twisted Pair (RJ45 Connector)  
AUI (DB15 Male Connector)  
Fast Ethernet Interface Modules  
Fast Ethernet Interface Modules are, in essence, EPIMs for the Fast Ethernet  
networking technology.  
EPIM-100TX:  
EPIM-100FX: Fast Ethernet Multimode Fiber Optics (SC Connector)  
EPIM-100F3: Fast Ethernet Single Mode Fiber Optics (SC Connector)  
Fast Ethernet UTP (RJ45 Connector)  
EPIM-100FMB: Fast Ethernet Multimode Fiber Optic Buffered Uplink  
(SC Connectors)  
Fast Ethernet Interface Modules will not operate in standard  
Ethernet devices. The reverse situation is also true.  
NOTE  
Port Interface Modules  
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PIMs and BRIMs  
TPIMs  
TPIMs are Token Ring Port Interface Modules. A TPIM provides a single Token  
Ring connection. If the Token Ring device the TPIM has been placed in allows it,  
the TPIM connection can be used as either a station port or a RI/RO port. All  
TPIMs use active Token Ring circuitry. The available TPIMs and the connectors  
and media they support are listed below:  
TPIM-F2:  
TPIM-F3:  
TPIM-T1:  
TPIM-T2:  
TPIM-T4:  
Multimode Fiber Optics (ST Connectors)  
Single Mode Fiber Optics (ST Connectors)  
Shielded Twisted Pair (DB9 Connector)  
Unshielded Twisted Pair (RJ45 Connector)  
Shielded Twisted Pair (RJ45 Connector)  
FPIMs  
FPIM stands for FDDI Port Interface Module. The FPIM is a single link for  
connection to a single cable in an FDDI network. The operation of an FPIM (what  
type of FDDI port it behaves as) is determined by the FPIM slot it is inserted into.  
The FPIMs available and their supported media are listed below:  
FPIM-00:  
FPIM-01:  
FPIM-02:  
FPIM-04:  
FPIM-05:  
FPIM-07:  
Multimode Fiber Optics (MIC Connector)  
Multimode Fiber Optics (SC Connector)  
Unshielded Twisted Pair (RJ45 Connector)  
Shielded Twisted Pair (RJ45 Connector)  
Single Mode Fiber Optics (MIC Connector)  
Single Mode Fiber Optics (SC Connector)  
4-4  
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PIMs and BRIMs  
APIMs  
The Asynchronous Transfer Mode (ATM) Port Interface Modules, or APIMs, are  
designed to allow connection to differing ATM networks, supporting not only  
different media, but different speeds of ATM transmission. When selecting an  
APIM, the Network Designer must ensure that the APIM supports both the  
required media and the technology to be used. The media and technologies  
supported by the available APIMs are listed below:  
APIM-11:  
APIM-21:  
APIM-22:  
APIM-29:  
APIM-67:  
Multimode Fiber Optic TAXI connection  
Multimode Fiber Optic OC3c connection  
Single Mode Fiber Optic OC3c connection  
Unshielded Twisted Pair STS3c connection  
Thin Coaxial Cable DS3 connection  
WPIMs  
Wide Area Network Port Interface Modules, or WPIMs, act in much the same  
manner as APIMs. Each WPIM is designed to provide connections to a particular  
type of Wide Area Networking technology.  
WPIM-SY:  
WPIM-T1:  
WPIM-E1:  
WPIM-DDS:  
WPIM-DI:  
Synchronous link  
T1 or Fractional T1 link  
E1 or Fractional E1 link  
56K link  
Drop-and-Insert WAN link  
Port Interface Modules  
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PIMs and BRIMs  
Table 4-1 provides basic information regarding the available PIMs and the  
connectors, media, and technologies they support.  
Table 4-1. PIM Reference Table  
PIM  
Technology  
Ethernet  
Media  
AUI  
Connector  
EPIM-A  
DB15 (Male)  
RG58  
EPIM-C  
EPIM-F1  
Ethernet  
Ethernet  
Thin Coaxial  
Multimode  
Fiber Optics  
SMA  
EPIM-F2  
EPIM-F3  
Ethernet  
Ethernet  
Multimode  
Fiber Optics  
ST  
Single Mode  
Fiber Optics  
ST  
EPIM-T  
EPIM-X  
Ethernet  
Ethernet  
UTP  
AUI  
RJ45  
DB15  
(Female)  
Fast Ethernet Interface  
Module-100TX  
Fast Ethernet  
Fast Ethernet  
Fast Ethernet  
Fast Ethernet  
Token Ring  
UTP  
RJ45  
SC  
SC  
SC  
ST  
Fast Ethernet Interface  
Module-100FX  
Multimode  
Fiber Optics  
Fast Ethernet Interface  
Module-100F3  
Single Mode  
Fiber Optics  
Fast Ethernet Interface  
Module-100FMB  
Multimode  
Fiber Optics  
TPIM-F2  
Multimode  
Fiber Optics  
TPIM-F3  
Token Ring  
Single Mode  
Fiber Optics  
ST  
TPIM-T1  
TPIM-T2  
TPIM-T4  
Token Ring  
Token Ring  
Token Ring  
STP  
UTP  
UTP  
DB-9  
RJ45  
RJ45  
4-6  
Port Interface Modules  
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PIMs and BRIMs  
Table 4-1. PIM Reference Table (Continued)  
PIM  
Technology  
FDDI  
Media  
Connector  
FPIM-00  
FPIM-01  
Multimode  
Fiber Optics  
FDDI MIC  
SC  
FDDI  
Multimode  
Fiber Optics  
FPIM-02  
FPIM-04  
FPIM-05  
FDDI  
FDDI  
FDDI  
UTP  
STP  
RJ45  
RJ45  
Single Mode  
Fiber Optics  
FDDI MIC  
FPIM-05  
APIM-11  
APIM-21  
APIM-22  
FDDI  
Single Mode  
Fiber Optics  
SC  
SC  
SC  
SC  
ATM (TAXI)  
ATM (OC3c)  
ATM (OC3c)  
Multimode  
Fiber Optics  
Multimode  
Fiber Optics  
Single Mode  
Fiber Optics  
APIM-29  
APIM-67  
ATM (STS3c)  
ATM (DS3)  
WAN (56K)  
UTP  
RJ45  
RG58  
RJ45  
RJ45  
Thin Coaxial  
Custom  
Custom  
WPIM-DDS  
WPIM-DI  
WAN (Drop &  
Insert)  
WPIM-E1  
WPIM-SY  
WAN (E1)  
Custom  
Custom  
RJ45  
WAN  
(Synchronous  
DTE)  
26-pin  
RS530A  
WPIM-T1  
WAN (T1)  
Custom  
RJ45  
Port Interface Modules  
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PIMs and BRIMs  
Bridge/Router Interface Modules  
In the same way that Cabletron Systems supplied a method for connecting a  
single network technology to different types of media, the Bridge/Router  
Interface Module, or BRIM, allows one networking technology to be connected to  
either a separate, segmented network or to a completely different networking  
technology.  
The addition of a BRIM to a networking device, be it a standalone Ethernet  
repeater or a sophisticated management module within a modular chassis, allows  
the device that the BRIM is configured in to access another network. The  
interconnection of the device and the additional network is handled by the  
internal operation of the BRIM.  
In effect, the BRIM takes the concept of the PIM a step further. Rather than  
internalizing a transceiver, the BRIM internalizes a dual-interface bridge or router,  
supplying segmentation and internetworking capabilities to any BRIM-capable  
device. As these capabilities are needed, a BRIM can be added to any  
BRIM-capable device. This gradual upgrade path allows Network Designers to  
plan ahead for the incorporation of new technologies without having to pay for  
the connection until it is needed.  
Types of BRIMs  
There are a number of different BRIMs available, and each has different  
capabilities and characteristics. The foremost of these characteristics are  
Before including any BRIM in a network design, consult your  
Cabletron Systems Sales Representative to ensure that the  
NOTE  
BRIM under consideration will operate properly in the device  
being considered for use.  
BRIM-E6  
The BRIM-E6 provides a single Ethernet segment through an EPIM slot. This  
EPIM slot may be configured with any EPIM module and operates as a normal,  
bridged Ethernet interface. The BRIM provides Ethernet bridging between the  
front panel EPIM slot and the BRIM interface within the device.  
BRIM-E100  
The BRIM-E100 operates in the same fashion as a BRIM-E6, but provides a  
connection to a 100 Mbps Fast Ethernet link. The BRIM-E100 provides one front  
panel EPIM-100 port which supports any of the Fast Ethernet Interface Modules.  
4-8  
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PIMs and BRIMs  
BRIM-F6  
The BRIM-F6 is an FDDI bridging device used to connect a standalone device to  
an FDDI network. The BRIM-F6 provides two user-configurable FPIM slots,  
allowing the Network Designer to specify and use any type of standard FDDI  
media for connection to the BRIM. The BRIM can be configured to provide either  
single attached or dual attached connections to the FDDI network, and can also be  
configured for dual-homing operation.  
If the BRIM-F6 is used as a dual-attached device, the two FPIMs that are  
incorporated into the BRIM do not have to be of matching media. Cabletron  
Systems recommends that, whenever possible, the media types of each FPIM in a  
single BRIM-F6 match for the sake of consistency and ease of cable and connector  
management.  
BRIM-A6  
The BRIM-A6 provides a single ATM uplink for the LAN device it is placed in.  
The BRIM-A6 supports a variety of media types and ATM speeds and  
implementations. The operation and media characteristics of the ATM uplink  
provided by the BRIM-A6 are dependent upon the type of APIM that is placed in  
the BRIM’s single APIM slot. The BRIM-A6 will not operate without an APIM.  
The BRIM-A6 is also available in a version incorporating a redundant connection,  
the BRIM-A6DP.  
BRIM-W6  
The BRIM-W6 supports one WAN link through a number of different WAN  
technologies. The BRIM-W6 provides one front panel WPIM slot, into which a  
WPIM module matching the functionality required of the WAN link can be  
placed. The BRIM-W6 will not function without a WPIM module, which  
determines the operational characteristics of the BRIM.  
Bridge/Router Interface Modules  
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PIMs and BRIMs  
The available BRIMs and the technologies they support are detailed in Table 4-2.  
This table can be useful for the selection of a BRIM when designing a workgroup  
requiring a connection to a particular networking technology.  
Table 4-2. BRIM Reference Table  
BRIM  
BRIM-E6  
Technology  
Ethernet  
Connector Type  
EPIM  
BRIM-E100  
Fast Ethernet  
Fast Ethernet  
Interface Module  
BRIM-F6  
FDDI  
ATM  
ATM  
WAN  
FPIM (2)  
APIM  
BRIM-A6  
BRIM-A6DP  
BRIM-W6  
APIM (2)  
WPIM  
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Chapter 5  
Network Design  
The following chapter discusses some of the more common approaches to workgroup network design.  
The network design process is the formation of the network from initial concept  
to the plan of implementation. In this Networking Guide, for the sake of brevity,  
the process of network design is separated from the process of network  
configuration. Network design is presented and treated as the decisions leading  
up to the selection of hardware, and network configuration is the process of  
putting hardware together to create a functioning network.  
When designing a network installation or configuration, draw  
the network. At the very least, make a rough sketch of each  
NOTES  
aspect of the network design process. Seeing the various parts  
of your design will help you identify strengths and weaknesses  
and make it easier for you to achieve a grasp of the network as  
a whole.  
Similarly, draw out the network configuration once you begin  
selecting hardware.While it is not necessary to represent every  
port, labeling modules and showing the connections made  
between them can point out potential problems before they are  
cemented into the configuration.  
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Network Design  
As this Networking Guide is concerned with the decisions made regarding  
networking hardware and not with the administration of networks or the specific  
uses to which they are put, several aspects of the overall process of network  
design are not treated in this document, such as the selection of a Network  
Operating System (NOS), the choice of applications or of workstation types, or  
other specific decisions generally out of the purview of Cabletron Systems as a  
provider of networking hardware. These aspects of network design will, however  
have an impact on the performance of networks, and should be fully investigated  
before designs are attempted.  
This chapter does not discuss the relative merits of one  
networking technology over another. For information on the  
NOTE  
different strengths of the available technologies, refer to the  
Cabletron Systems Networking Guide - MMAC-FNB Solutions.  
The Role of the Workgroup  
A workgroup is a group of network end stations that are related in some way. The  
conditions of this relationship are determined by the Network Manager, and can  
be based on anything from device type to user occupation or even device color. As  
the workgroup is the operating portion of the network, where information is  
created and given direction, the workgroup is the portion of the network that  
creates traffic and network congestion. As such, it is the most complicated portion  
of the network to design.  
Very few networks are made up of one workgroup. It is a mistake, however, to  
underestimate the importance of a properly designed and well-planned  
workgroup, as the vast majority of enterprise networks are collections of  
workgroups that are connected to one another. The various workgroups all have  
different needs and implementations, and are tied together to form a cohesive and  
capable enterprise network. A logical, well-thought-out workgroup plan and a  
skillful execution of the creation of workgroups according to a firm set of criteria  
goes a long way toward ensuring that the network which results will be  
functional, flexible, reliable, and sufficiently robust to handle the demands placed  
on it by users.  
The idea of the workgroup in the network roughly translates to the use of  
segmentation. Ideally, segmentation should be planned between separate  
workgroups or between collections of related workgroups, not within  
workgroups. The workgroup concept divides the network according to a cohesive  
plan in the interests of reliability, efficiency, or ease of recovery. While all of these  
are important factors in the operation of the network, certain choices made in the  
design of networks, from technology and topology to the organization of stations  
and the segmentations method used if any, will improve some aspects of the  
network at a cost to others. Striking the proper balance of these factors is the  
responsibility of Network Managers, who must investigate and determine the  
needs and preferences of the proposed network’s users.  
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Network Design  
Workgroup Establishment Criteria  
This section examines some of the methods that may be used to divide the  
population mass of end users of a network into cohesive and defined  
workgroups.  
Geographical Proximity  
Organizing workgroups by geographical proximity creates workgroups made up  
physical locations of departments may correspond exactly to a facility layout, the  
geographical proximity criteria of workgroup organization does not take function  
into account. As the deciding criteria for this type of workgroup organization is  
location only, geographical proximity is often the least efficient workgroup  
creation method in terms of performance, reliability, and troubleshooting.  
Workgroups  
A8  
A6  
A4  
A2  
A7  
A5  
A3  
A1  
L1  
: Service Workstations  
: Sales Workstations  
: Research Workstations  
: Receiving Workstations  
Figure 5-1. Geographical Proximity Workgroups  
Having well defined rules of geographical proximity as the deciding factor in  
workgroup design does, however, make the physical act of fault recovery easier in  
many networks. If an entire location is suffering errors or loss of network  
operation, there is a defined physical location to begin examining network  
devices for faults.  
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Network Design  
Departmental Organization  
Corporations, companies, and agencies all separate employees by primary  
function. No one person “does it all,” and most employees are specialists in the  
sense that they perform one function or a series of functions that are assigned to  
them by their job descriptions. These functions dictate what types of information  
and network usage they require: manufacturing personnel deal primarily with  
manufacturing information; accounting personnel deal primarily with sales,  
profit, and expenditure information; and research personnel primarily perform  
design and testing operations.  
Since most of the time business departments are involved with sharing  
information among other members of their department or a group of related  
departments (Accounting, Personnel, and Payroll, for example), the division of  
the end user population into workgroups based on corporate function and  
separated by bridges, switches, or routers tends to improve network performance  
by keeping information passed within each department from impacting the flow  
of information within other departments. This provides natural divisions within  
local traffic from congesting the network where it is used by other departments.  
: Sales Workstations  
: Research Workstations  
: Receiving Workstations  
: Workgroup A  
: Workgroup B  
: Workgroup C  
Figure 5-2. Corporate Organization Workgroups  
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Network Design  
As the creation of workgroups based on departmental organization mirrors the  
operation of the company, the expandability of the network is simplified; since  
departmental growth can often be predicted in stable or growing companies, the  
network can be designed to allow for simplified expansion in the departments  
most likely to grow.  
Without the use of management software to monitor the operation of workgroups  
determined by departmental organization, troubleshooting and fault recovery can  
be difficult in a network of this kind. As the end users are not necessarily located  
in the same area, faults which affect the workgroup must be looked for in several  
locations.  
An even trade-off is made in reliability in networks organized in this fashion.  
While the organization of the network into departmental workgroups increases  
the inherent complexity of the network by creating several segments based on  
function, the loss of a workgroup will disrupt the operation of only that  
workgroup, allowing the operation of other workgroups to continue with no  
disruption other than the loss of communication with the faulty  
workgroup/department.  
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Network Design  
Common Function  
Segmentation by common function is often used to provide further division of the  
network within larger overall departments, or to facilitate the use of certain  
network applications by specific end users common throughout much of the  
department. An example of this might be the creation of a Documentation  
workgroup in a corporation within which each department had a dedicated  
Documentation person handling recording and reporting. This would create  
workgroups of the members of each department (R&D, Sales, Receiving, etc.) and  
one workgroup which encompassed only the Documentation personnel of each  
department, who, although working in different departments, all require access to  
the same functions through the network.  
: Sales Workstations  
: Research Workstations  
: Receiving Workstations  
: Workgroup A  
: Documentation Personnel  
: Workgroup B  
: Workgroup C  
: Workgroup D  
Figure 5-3. Common Function Workgroups  
The creation of workgroups based on common function enhances the  
performance of those dedicated functions at a cost to the performance of the  
network as a whole. In addition, the management demands placed on a network  
by common function networks distributed across an entire facility or corporation  
are much the same as those of a corporate organization workgroup scheme, but  
even more intense.  
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Network Design  
Priority Organization  
Priority organization is a flexible term that refers to the Network Manager  
assigning devices to workgroups based on specific priorities. As such, it is the  
most flexible scheme for creating workgroups, because it is based solely on the  
relative importance of certain network characteristics to individual end users and  
equipment. Priority organization can be used to create high-speed,  
high-reliability, or rapidly recovering workgroups to those stations requiring  
those characteristics. Unfortunately, it combines some of the worst features of the  
other methods of arranging workgroups as the cost of this level of control.  
An example of priority organization is the common practice of connecting all the  
file servers for a particular facility to a high-speed network access device in a  
single location, regardless of the location of the workgroups needing access to  
them. This practice is known as “server farming,” and is used, in many cases, to  
keep network users from attempting to repair, reconfigure, or use the servers in  
imaginative, and often hazardous, ways.  
f/s  
f/s  
f/s  
: Sales Workstations  
: Research Workstations  
: Receiving Workstations  
f/s : File Servers  
: Priority Workgroup  
: Standard Workgroup  
Figure 5-4. Priority Organization Workgroups  
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Network Design  
Priority organization of this manner in a single-segment network involves  
providing stations in the priority workgroups with qualities of media and  
network connection based on that priority. For example, the stations in the server  
farm might have redundant connections to the network in the event that one cable  
failed, use a media resistant to interference, such as fiber optic cabling, or might  
be best served by a centralized location. A priority organization workgroup or  
sub-section of a workgroup that is located on the same network segment as its  
most common users is usually an efficient and safe use of resources, and will not  
impede the operation of the network.  
While keeping the users separate from the devices that they need to access on a  
regular basis does enhance the Network Manager’s control over its use and  
operation, it does reduce network performance in networks using segmentation.  
By connecting stations to the network based on their relative importance, the  
priority organization method makes little or no accommodation for the  
localization of network traffic, which is the purpose of segmentation. If a file  
server is located in a server farm workgroup, segmented from the rest of the  
network, every user needing access to any file server must cross a segmenting  
device such as a bridge or switch, introducing access delays as the device reads in  
the packet, examines the packet, determines whether to send it on or discard it,  
checks the packet for errors, and acts on its forward or discard decision. The  
necessity of crossing the segmenting device on a regular basis destroys the  
network availability that is gained by bridging, as local traffic is no longer kept  
local.  
The use of priority organization also introduces additional troubleshooting  
complications. If a station in the Sales department cannot access their file server, is  
it because the server has failed, the bridge connecting the server to that  
department is in error, the connection from the Sales department to the bridge is  
down, or the connection from the employee’s workstation to the rest of the Sales  
workgroup is faulty?  
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Network Design  
Selecting Workgroup Technologies  
The selection of a network technology at the workgroup level is a very important  
decision, and one that should be made only after careful consideration and  
evaluation. Before deciding on a network technology to be used by the  
workgroups, make sure you are familiar with the operation of each type of  
technology, the strengths and shortcomings of those technologies, and the special  
design considerations that each technology imposes on the network. Chapter 2 is  
a good place to go for initial information, but the text deliberately avoids  
examining the technologies in great detail. For more detailed treatments of the  
technologies, refer to the Cabletron Networking Guide - MMAC-FNB Solutions or  
any of the Cabletron Systems Technology Overviews. There are also several texts on  
network technologies available through academic and technical booksellers.  
The selection of a workgroup technology is an analysis of functionality. It is the  
job of the Network Manager or persons designing the network to determine  
which factors of the network design are the foremost requirements.  
The most common determining factors in selecting a network technology are  
performance (speed of operation), reliability, ease of configuration,  
troubleshooting, and cost. Cost is a separate issue from price, as cost is based on  
the inherent expenses of the technology, whereas price is highly dependent upon  
the vendor supplying the products and the quality of the products and service  
associated with them.  
This information is not intended to be the only guide for deciding upon a  
networking technology. The selection of a technology determines the capabilities  
and characteristics of the entire network, and is one of the most important and  
long-term decisions that you make when designing a network.  
For this reason, once you feel that you have selected a suitable technology, do  
further research on that technology if you have any questions about its operation  
or the means by which a network is created using that technology. Contact your  
Cabletron Systems Sales Representative for information, or read any of the  
technical books available on the subject matter.  
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Network Design  
Creating a Manageable Plan  
A well thought-out and carefully designed network is still difficult to  
troubleshoot if no one else knows how it is organized. There may come a time  
when the designer of the network is not available, for whatever reason, and  
troubleshooting or re-configuration needs to be done. It may also become  
necessary to expand the network to accommodate a growing use of workstations  
or increases in personnel. It is at these times that a properly thought-out,  
implemented, and recorded network plan becomes a life saver.  
The network plan is the “concept” behind the entire network. It deals with  
everything from where devices will be located and where the cables will be run to  
the advanced or future technologies that the network may incorporate as it grows  
or changes.  
A good network plan can go a long way to eliminating headaches during the  
configuration and implementation stages. Have an overall design in mind when  
you begin planning individual configurations, and the network will be much  
easier to see as a whole. The network plan, in the design stages of networking, can  
point out areas that need additional work, help you locate possible trouble spots,  
and allow you to make the network more capable, more reliable, and more  
expandable than a haphazardly-assembled collection of cables and hardware.  
Logical Layout  
Component Location  
The actual locations of the networking hardware is an important aspect of logical  
layout. As a network designer, you should determine how you want to treat the  
placement of devices and hold to that decision whenever possible.  
Some of the commonly considered aspects of logical layout are as follows:  
Workgroup Location - If a workgroup is centered in a particular area of a  
facility, you may wish to locate the networking hardware directly related to  
that workgroup in the same physical area as the workgroup.  
Security - This is related to Centralization and Control (see below). In some  
cases, for security reasons, you may wish to place networking hardware in  
locations where they are not easily accessed by unqualified personnel. The  
usual course of action for security is to place networking equipment in an  
enclosed equipment cabinet or a locked wiring closet.  
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Network Design  
Centralization and Control - If you require more control over the networking  
hardware than you can get from locking it away, you can place many devices  
in one central location such as a Network Management office. For a small  
facility, it is entirely possible that all the networking hardware except end user  
workstations will be located in an office such as this. An arrangement of this  
sort provides total control over the use and configuration of the hardware in  
the hands of the Network Manager. This centralization also makes the location  
and isolation of faults much faster, as several problems may be identified and  
eliminated without the Network Manager ever having to leave the room.  
Cabling  
The method by which cabling is run from devices to end user stations is an  
important part of a manageable, expandable plan. Logically defining a workable,  
flexible, and expandable cabling system for a facility goes a long way toward  
making repairs and expansions to the network less difficult. This Networking  
Guide will address the issue of cabling plans briefly, but other Cabletron Systems  
documentation and specific product Installation Guides dicuss cabling  
requirements in greater detail.  
The most important thing to remember when planning cabling installations is  
that attention to detail will pay off. You may save a few hours at installation by  
not labeling your cables, but those saved hours will be more than spent later  
when you are attempting to locate the cable connected to John Doe’s workstation  
so that he can be moved to a different workgroup.  
Design cable installations with the future in mind. It is less expensive to install  
an extra 40 or 50 cables during the initial installation than to have to go back  
and pull 10 cables on two different occasions because a department grew.  
Keep cabling neatly organized. Bundle several cables together and secure  
them to places where they may be easily accessed. If one bundle of cables is  
associated with a specific workgroup or facility location, label that bundle  
periodically to eliminate any later confusion.  
Don’t connect raw facility cable to equipment ports. Facility cable should be  
connected to punchdown blocks, patch panels, or distribution boxes. These are  
simple wiring devices which allow you to use small jumper cables to connect  
the networking hardware to the facility cabling. These devices make labeling  
cables and changing connections much easier.  
Label everything. Every cable installed should be identified in at least two  
places (each end) by a numerical code. Every patch panel or distribution box  
port should be labeled as well. Many network wallplates have spaces where  
wallplate numbers can be displayed.  
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Network Design  
Use a standard, decipherable labeling code for cable and hardware. A label  
reading L2N5W2C1S243 may look like gibberish now, but if you know that  
the letter codes indicate locations or conditions of installation, it can be quite  
helpful. Table 5-1, below, shows the meanings of the codes and numbers of  
this example.  
Cable Label: L2N5W2C1S243  
Table 5-1. Cable Code Key  
Code  
Code Definition  
Meaning  
L2  
Location 2  
Network 5  
Workgroup 2  
Closet 1  
Engineering Building  
Network Map #5  
N5  
W2  
C1  
Production Controls Workgroup  
Wiring Closet #1  
S243  
Station 243  
Wallplate #243  
The code key depicted above is only an example, and is not  
indicative of any industry standard or generally accepted cable  
marking practices.  
NOTE  
Fault Aversion  
A good network design strategy realizes the importance of avoiding future  
trouble spots. It is possible to design a network such that the most dangerous of  
these trouble spots are either eliminated, covered by contingencies, or their effects  
are minimized. This aspect of network design is called “fault aversion.”  
A fault averse network uses the capabilities of available hardware and the  
fault-tolerance or recovery features of the technologies of the network to provide  
for three things: the elimination of single points of failure, the availability of  
redundancy, and the quick and easy isolation of and recovery from errors or  
problems.  
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Network Design  
Single Points of Failure  
A single point of failure is any one device, cable or connection that, if it should fail  
or be removed from the network, would disable all or a sizable part of the  
network.  
Most Cabletron Systems hardware seeks to eliminate single points of failure from  
within the device, by providing for redundant links or the distribution of essential  
functions among several related devices. Using devices in accordance with their  
fault-tolerant designs makes the network more able to continue operations  
automatically in the event of a component or cable failure.  
An example of a very obvious single point of failure is a shared segment of thick  
coaxial cable in an Ethernet network. All of the stations rely on the availability of  
the one coaxial segment. Should the segment fail, due to a break in the cable or the  
removal of a terminator, the network fails. A design eliminating the cable as a  
single point of failure might use several thin coaxial cable segments attaching to a  
repeater or modular chassis. Any one coaxial cable segment may fail without  
bringing down the other coaxial cable segments. The repeater can be seen as a  
single point of failure, but only from the point of view of the connection between  
segments, as the segments themselves will continue to operate without the  
repeater.  
The location and elimination of single points of failure is a very difficult step in  
network planning. It is important to set realistic limits on the elimination of these  
single points of failure. A network that completely eliminates single points of  
failure will be more expensive and complex than a network that eliminates only  
the most dangerous single points of failure.  
Redundancy  
Redundancy is the provision of or availability of backup systems. Redundancy is  
designed into a fault-averse network to allow a system or connection to quickly  
be activated to take the place of a failed system. Redundancy features are most  
often inherent parts of the networking technology being used, but the network  
must be designed to take advantage of those features.  
When designing a network, check the descriptions of the products to see if they  
support the creation of redundant links to devices. It is often a good idea to have  
some form of back-up capability for the network. For example, having more than  
one link from a workgroup device or stack to the centralized network repeater or  
switch means that if one of the two links fail, the second link can be activated and  
used. This is a very useful approach in areas where cable damage is likely.  
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Network Design  
Isolation and Recovery  
No matter how much redundancy is designed into a network, and no matter how  
much the single points of failure are eliminated, the law of averages eventually  
catches up to any network, and a failure will occur. Once the failure does occur,  
the isolation and recovery process begins. If a network is designed to eliminate  
confusing layouts and make the troubleshooting procedure efficient and effective,  
the amount of time a network is down is reduced. Comprehensive planning of  
workgroups and backbones is the most directly effective way to design isolation  
and recovery features into the network. Additionally, the use of built-in  
diagnostic systems, such as LED indicators, can provide quick and easy gathering  
of network operation information.  
An example of this is the automatic wrapping of the dual ring structure of FDDI  
networks. If a station on the dual ring is lost, the ring wraps back upon itself at the  
two points between which the signal was interrupted or lost, closing the ring back  
up and allowing traffic to continue passing. A good FDDI network design takes  
advantage of this recovery feature by placing the most essential devices, ones  
which are not intended to fail often or be shut down, on the dual ring, where they  
will benefit from the automated recovery feature.  
Network Maps and Record Keeping  
A large portion of the process of expanding an existing network or  
troubleshooting faults and problems is determining what the current state of that  
network is. Keeping a running record of the status of the network, its  
configuration, and any changes made to that configuration, can go a long way  
toward simplifying the expansion of the network or migration to new  
technologies.  
Tracking Functions  
Networks are inherently complex things. There is a large amount of detailed  
information that needs to be recorded, and there are many different people who  
need differing levels of information about the network. Since the layers of  
complexity required by different people cannot always be crammed onto one  
network map, it may be very useful to keep a series of maps, each showing  
differing levels of complexity.  
For example, a network map set might include a facility map showing the  
division of areas into workgroups, a map showing the location, layout, and type  
of physical cabling, one showing the locations of networking hardware, and  
individual maps showing the locations and types of physical devices.  
If you are using a network management package, such as Cabletron Systems  
SPECTRUM Element Manager, it is helpful to have a network map which shows  
the MAC addresses and IP addresses of the devices on the network.  
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Network Design  
Tracking Changes  
Your network maps will be used for keeping track of a large amount of  
information, which will naturally change over time. As the network grows or is  
altered, the devices that make up the network will change, new workgroups will  
be added, segmented off from larger workgroups or combined with smaller ones.  
It is, therefore, important to keep track of the changes made to the network, and  
the network map is a good place to do this.  
A network map that indicates a patch panel, punchdown block, or breakout box  
should identify that patch panel by a numerical or alphabetical code. This code  
should indicate a patch panel chart, which can be referred to for connection  
information.  
Any network device which appears on the general network map should be  
identified by some short and easily read code. This code refers to a separate list of  
the actual type of device. For example, the network map might show a diamond  
shape with “B882” written in it. A look at the chart or table of devices associated  
with this map indicates that the “B” in the code indicates a bridge, and bridge  
“882” is a standalone 2-port Cabletron Systems Ethernet bridge, NBR-220. If in the  
future this device is upgraded, the map can remain the same, but the device code  
table or chart can be changed. If, for example, the NBR-220 was upgraded to an  
Ethernet switch in a small chassis, the chart entry for “B882” could be changed to  
read “Cabletron Systems ESXMIM 6-port Ethernet switch in MMAC-M3FNB  
small modular chassis” without requiring any changes to the overall network  
map.  
Network Expandability  
Networks tend to grow. As businesses change and networking capabilities  
become more and more a part of the business process, networks grow in size or  
complexity and capability. For this reason, it is important, in any network, to plan  
for future expansion.  
Expansion does not only mean being able to increase the total port count;  
expandability includes the later incorporation of new and future technologies,  
increasing the power, speed, and reliability of the network.  
The Cabletron Systems PLUS architecture, a key component in the design of the  
MMAC, MMAC-Plus, and MicroMMAC device families, is an effort to make  
planning for the future easier. By providing the capability for advanced  
functionality to be included as it is needed, the PLUS architecture smooths the  
upgrade and expansion path. For information on the various aspects of the PLUS  
architecture, contact your Cabletron Systems Sales Representative.  
Network Expandability  
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Network Design  
The Workgroup as the Network  
In many cases, the only network that a facility requires is a single workgroup.  
Depending on the bandwidth, segmentation, and security requirements of any  
facility, the single workgroup may be all that is needed. In these situations, the  
only network to be considered is the workgroup.  
When the only networking concern is the workgroup, issues such as  
internetworking and inter-workgroup communications are not a part of the initial  
design strategy. A single workgroup design can be customized to any extent that  
the Network Designer wishes, without concern for the inclusion of  
internetworking or security.  
It is important in these situations, however, to plan for future expansion. What  
will happen if the number of stations to be placed on the network increases in the  
coming years? How willing are the network’s end users to pay to completely  
replace all the equipment that makes up the workgroup in order to add special  
functions? What actions will be taken if the facility expands or constructs another  
separate office? All of these questions should be examined before selecting a  
single networking product.  
The Workgroup in the Larger Network  
In most situations, the workgroup is only a part of a larger enterprise network. In  
these situations, consideration must be given to the organization of the enterprise  
network when designing the workgroup. Workgroups in an enterprise network  
quite often have specific internetworking needs. The Ethernet workgroup in the  
Materials Processing department may need a connection to the corporate Token  
Ring backbone network, or the small branch office network may require a Wide  
Area Network connection back to the head offices.  
The specific situation faced at any installation site is one of two conditions: either  
the workgroup(s) must be connected to an existing facility backbone or a  
backbone must be set up to connect a series of newly-designed workgroups. The  
sections that follow describe some of the approaches taken to facility backbone  
design, their strengths and weaknesses.  
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Network Design  
What Is a Backbone?  
A backbone is a network segment or cable which is used to provide for the  
interconnection of a number of smaller workgroups or self-contained networks.  
The outlying networks, workgroups, or hubs communicate with one another  
through the backbone network.  
The use of a dedicated network acting as a backbone, tying all the separate  
networks together, is of benefit for several reasons.  
Using a single network to handle the extremely important connections  
between networks allows Network Designers to use highly reliable  
technologies and cables. These designs are frequently expensive, and using  
them, initially, in the backbone network provides the benefits of these  
technologies or media without requiring the expense of providing that level of  
service to all points of the network.  
A backbone network can be migrated out to the workgroups as the  
facility-wide network grows. As more users are added, it is often much easier  
to attach a concentrator or hub to a small backbone network than to continue  
expanding workgroups that may be already quite congested. In addition, the  
backbone can provide a point from which a higher-speed technology can be  
‘painted out’ to the rest of the network as needs dictate and as money becomes  
available.  
Since the amount of communications passing between several workgroups or  
hubs in an entire facility or campus is often quite large, backbone networks  
often use higher-speed networking technologies than those of the workgroup  
networks. Avery common workgroup and backbone scenario involves several  
Ethernet workgroups in a building or campus connected to an FDDI backbone.  
This offers the communications passing between the separate Ethernet  
networks, operating at under 10 Mbps, to access a highly reliable and available  
100 Mbps network for communications between workgroups.  
Methods of Configuring Backbones  
Backbone networks can be set up in a number of different ways. This Networking  
Guide presents three of the most common means of configuring backbone  
networks. Almost any backbone network implementation may be designed from  
the following basic backbone types:  
Distributed Backbone  
Collapsed Backbone  
Device Collapsed Backbone  
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Network Design  
The Distributed Backbone  
One method of creating a backbone network is to sequentially string all of the  
workgroup networks or hubs together. Cabling is run from one workgroup hub to  
the next, providing the necessary connections. This method of configuring a  
except ATM, which requires a device backbone configuration (detailed later in  
this chapter).  
hub  
hub  
hub  
hub  
2094n10  
Figure 5-5. Distributed Backbone  
A distributed backbone is usually the least expensive backbone network selection,  
as the only products required is the cabling that runs from one workgroup  
network to another. The problems inherent in the distributed backbone network  
are somewhat limiting, however:  
Connectivity Requirements - FDDI and Token Ring networks must form a  
complete, unbroken ring. Ethernet backbones are most effective if all  
workgroup networks are attached to a shared bus, such as a thick coaxial cable.  
Limited Expandability - While it is possible to simply add stations to a thick  
Ethernet backbone, the ring-dependent technologies (Token Ring and FDDI)  
require that existing cable be cut and terminated or replaced with additional  
cable runs when new workgroup networks are added to the backbone.  
Troubleshooting Complexity - If a distributed backbone suffers an error or a  
faulty cable, locating the fault in the network often takes up much of the total  
troubleshooting time. If a cable is at fault, the Network Manager may spend a  
lot of time pulling and testing new cabling.  
Limited Control - The use of a distributed backbone makes the isolation of  
workgroups from the rest of the overall network somewhat time-consuming.  
If a workgroup in a distributed backbone must be disconnected from the other  
networks physically, the distributed backbone requires that a Network  
Manager go out to the physical location of the workgroup network and  
disconnect the required cables, making any additions or changes necessary to  
keep the backbone network whole and operating.  
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Network Design  
The Collapsed Backbone  
It is also possible to run cables from a central point, often a network management  
office or central wiring closet, out to each workgroup network and back. These  
cabling runs are then terminated at a central point such as a patch panel. The  
patch panel ports for each of the cable runs can then be connected to one another  
using jumper cables. As long as technology restrictions are not exceeded, chains  
and rings of workgroup networks can be created.  
hub  
hub  
hub  
hub  
Cross-Connected  
Patch Panel  
2094n11  
Figure 5-6. Collapsed Backbone  
Having the individual cable runs of the backbone connected to one another at a  
single point can make this configuration more expensive than the distributed  
backbone, however the added configuration and control options provided by the  
collapsed backbone often outweighs the associated costs.  
Connectivity Requirements - The collapsed backbone implementation brings  
all cables of the backbone to a central point, and the requirements of the Token  
Ring and FDDI technologies for an unbroken ring still apply.  
Ease of Expandability - Since the cables of the collapsed backbone originate  
from a patch panel in one location, adding new cable runs to accommodate  
new workgroups or to bypass outmoded ones is a simple matter of changing  
a few jumper cables. If the network cabling was planned far enough in  
advance, the facility cabling required to add new workgroups to the backbone  
network may be already in place, requiring only a set of jumper cables and a  
short amount of time to connect. The use of a collapsed backbone can ease the  
transition from a backbone network with no controlling hardware to a device  
collapsed backbone in the future.  
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Network Design  
Simplified Troubleshooting - Workgroups can be bypassed by simply  
reconfiguring a single patch panel. This can easily isolate a problem segment  
for troubleshooting, and keeps the backbone network from being kept in a  
fault condition.  
Moderate Control - The isolation of workgroups and the reorganization of the  
backbone network is simplified with the collapsed backbone, but the system  
does not incorporate any management features beyond the physical  
connections of facility cabling. For advanced and detailed network control  
operations, the device collapsed backbone (discussed below) is superior to the  
collapsed backbone alone.  
Devices as Backbones  
Once a collapsed backbone has been designed, it is a simple matter to connect the  
multiple backbone cables together through a device. Often this device is a  
multiport router, network switch, or a modular chassis. The use of a device of this  
type to make the connections between workgroups greatly increases the control  
that Network Managers have over the network, and may improve performance  
by streamlining the communications between networks.  
hub  
hub  
hub  
hub  
Ethernet Switch  
2094n12  
Figure 5-7. Device Collapsed Backbone  
The device collapsed backbone is the most expensive backbone because of the  
added cost of sophisticated, high-performance hardware to the costs of a  
collapsed backbone cabling layout. In many cases, the additional control and  
functionality of the device collapsed backbone configuration are so valuable that  
the cost is well worth it.  
Connectivity Requirements - The device collapsed backbone implementation  
brings all cables of the backbone to a single device, which takes care of the  
interconnection issues.  
Ease of Expandability - As all the workgroups of the network are connected  
through the backbone device, the expandability of the network is limited by  
the amount of expandability that the device is capable of. As with the design  
of facility cabling, planning for future needs will go a long way toward  
reducing future expenses and possibly avoiding a costly replacement upgrade.  
5-20  
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Network Design  
Simplified Troubleshooting - The device collapsed backbone, by connecting  
the workgroups through a manageable device, provides not only simplified  
troubleshooting, but the ability to detect some backbone faults before they  
become network failures.  
Extensive Control - The device collapsed backbone provides the highest level  
of network control. Workgroups and devices on the backbone can be included  
or bypassed with the click of a mouse or through the use of a terminal session.  
Physically adding workgroups to the network will still require the connection  
of facility cabling and jumper cables, but, as with the standard collapsed  
backbone, the usefulness of planning ahead cannot be over-emphasized.  
One danger of the device collapsed backbone is the existence of a single point of  
failure: the backbone device. If the backbone device fails, the backbone network  
will not operate. For more information on single points of failure and avoiding  
their creation in a network, refer to the Fault Aversion section of this chapter.  
Choosing Backbone Technologies  
The selection of a backbone technology is a similar process to the selection of  
workgroup technologies. As with the selection of a workgroup technology, make  
sure you are familiar with the operation of each type of technology, the strengths  
and shortcomings of those technologies, and the special design considerations  
that each technology imposes on the network. You may, again, wish to refer to the  
training information of this Networking Guide for initial instruction.  
The selection of a backbone technology requires a careful examination of the  
needs of your facility and the ways that the various technologies and organization  
styles can fit those needs. It is the job of the Network Manager or persons  
designing the network to determine which factors of the network design are the  
foremost requirements.  
The determining factors in selecting a backbone network technology are the same  
as those used in selecting workgroup technologies - performance (speed of  
operation), reliability, ease of configuration, troubleshooting, and cost. In the  
backbone network, it is quite common to plan far ahead, providing more  
bandwidth than you think you will need. If this is done correctly, it will facilitate  
the upgrading of the technologies of the outlying workgroup networks without  
requiring an immediate rebuilding of the backbone network.  
For this reason, once you feel you have selected a suitable technology, do further  
research on that technology to resolve any questions about its operation or the  
means by which a network is created using that technology. Contact your  
Cabletron Systems Sales Representative for information, or read any of the  
technical books available of the subject matter.  
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Network Design  
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Chapter 6  
Ethernet  
This chapter describes in detail the processes and decisions involved in designing an Ethernet  
workgroup using Cabletron Systems products.  
Once the proposed network has been broken into a number of workgroups, it is  
necessary to begin designing the actual solutions for those workgroups and  
selecting hardware for use in them. The information that follows details the  
procedures used to determine the Cabletron Systems networking hardware  
necessary for specific types of workgroup networks.  
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Ethernet  
Ethernet Workgroup Devices  
The following sections describe the various Cabletron Systems networking  
devices that may be used in an Ethernet workgroup implementation. These  
Ethernet devices are divided into two categories - shared Ethernet devices and  
switched Ethernet devices. Shared Ethernet devices are those which connect all  
stations and links to a single Ethernet collision domain. The switched devices  
provided a number of dedicated Ethernet collision domains and provide for  
discriminatory connections between those interfaces.  
Shared Devices  
There are several Cabletron Systems networking devices to consider when  
designing an Ethernet workgroup that will share a single Ethernet network  
segment. The available devices are listed in Table 6-1, below.  
Table 6-1. Shared Ethernet Workgroup Devices  
Max  
Management  
Product  
MR9T-E  
Type  
Media  
Port Count PIMs/BRIMs  
repeater  
stackable  
stackable  
stackable  
NONE  
UTP  
UTP  
UTP  
8
1 EPIM  
1 EPIM  
2 EPIMs  
1 EPIM  
a
SEH-22/32  
SEH-24/34  
SEH-22FL  
NONE  
12  
24  
12  
a
NONE  
a
NONE  
Multimode  
Fiber Optics  
SEHI-22/32  
SEHI-24/34  
SEHI-22FL  
stack base  
stack base  
stack base  
SNMP  
SNMP  
SNMP  
UTP  
UTP  
12  
24  
12  
1 EPIM  
2 EPIMs  
1 EPIM  
Multimode  
Fiber Optics  
MicroMMAC-22/32E  
MicroMMAC-24/34E  
stack base  
stack base  
RMON  
RMON  
UTP  
12  
24  
1 EPIM  
1 BRIM  
UTP  
2 EPIMs  
1 BRIM  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
considered when selecting networking devices for a particular workgroup  
implementation. The meanings of these fields and their various values are  
described below.  
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Ethernet  
Type  
The type column describes what functions the device in question performs. There  
are three basic types of devices covered by this table. Repeaters are standalone  
Ethernet multiport repeaters. They count as a single repeater hop for purposes of  
calculating maximum network size or propagation delay. Stackables are Ethernet  
repeaters that may stand alone or be connected to other stackable devices of the  
same type to form a single Ethernet stack, which acts as one repeater domain. The  
stackable base is an intelligent stackable device that can be used as the first device  
in a stack, and which will extend management capabilities to non-intelligent  
devices in the stack.  
Stack bases may not be used in any position in a stack except  
the base. They do not have the HubStack Interconnect Cable  
NOTE  
ports required to be stack members other than the base.  
Max Management  
The Max Management column indicates the highest level of management  
functionality that the standalone or stackable device provides. There are three  
levels of management functionality, or lack thereof. Devices with a Max  
Management of NONE have no management control and no management station  
interface. Devices capable of Simple Network Management Protocol (SNMP)  
management support Cabletron Systems SNMP implementation, which includes  
the functions of SNMP Management Information Base II (MIB II) and the  
Cabletron Proprietary MIB. RMON-capable devices include all SNMP functions  
and several of the nine standardized Remote MONitoring (RMON) groups.  
Media  
The Media column of the table indicates the type of networking cable that is  
supported by the device. The specifics of media support and connector type are  
dependent upon the individual product. More detailed information regarding the  
types and numbers of connectors on specific products can be found in the Product  
Descriptions section of this document or in the Cabletron Systems Networking  
Solutions Product Guide.  
Port Count  
The Port Count column indicates the number of fixed (non-BRIM or PIM) ports  
that are available on the device.  
PIMs/BRIMs  
The PIMs/BRIMs column indicates the number and type of Interface Modules  
that the device can support. These PIM and BRIM slots are ports available in  
excess of the number given for the device’s port count. Thus, an MR9T-E supports  
a total of nine ports: eight UTP ports and one EPIM port.  
Ethernet Workgroup Devices  
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Ethernet  
Switched Devices  
Ethernet segmentation and switching designs require some slightly different  
information and decisions. Several of the important factors to consider when  
selecting a segmentation-based workgroup scheme are listed along with the  
Cabletron Systems Ethernet switch products in Table 6-2, below.  
Table 6-2. Ethernet Workgroup Switches  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
NBR-220  
NBR-420  
NBR-620  
SNMP  
SNMP  
SNMP  
0
0
0
2
4
6
2 EPIMs  
4 EPIMs  
4 EPIMs  
2 BRIMs  
FN10  
SNMP  
RMON  
RMON  
UTP  
UTP  
12/24  
12  
12/24  
13  
0
ESX-1320  
ESX-1380  
1 BRIM  
1 BRIM  
Multimode  
Fiber Optics  
12  
13  
be considered in a network design. The Max Management, Media, and  
PIMs/BRIMs columns are defined in the same way as for shared Ethernet  
devices. The remaining two columns require some further treatment in terms of  
their relationship to Ethernet switches.  
Port Count  
Port Count indicates the number of fixed media ports there are on the device. In a  
case where a device has zero ports, it means that the device has no dedicated  
media ports, and all connections are made through user-configurable PIMs or  
BRIMs.  
Switch Interfaces  
The Switch Interfaces column indicates how many separate and distinct switched  
connections the Ethernet device is capable of recognizing. If multipoint media,  
such as coaxial cable, are connected to a switch interface, the Ethernet switch will  
switch only to that segment, not between individual stations on that segment.  
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Ethernet  
Ethernet Workgroup Design  
When designing a new workgroup, one of the first tasks to be confronted is the  
selection of a technology and an approach to the network. These selections are  
based on the organization of the workgroups, as discussed in Chapter 5, Network  
Design, the scale (or population) of the workgroups, and the anticipated  
bandwidth requirements of each workgroup or each station in the workgroup.  
In the examples which follow, the decision of a networking technology and  
approach to the workgroup has already been determined by the Network  
Designer. In the real world, these decisions will have to be approached in a  
sensible and thoughtful manner, because the selection of these aspects will  
determine the operational and design characteristics of the network for the long  
and short runs.  
The Home Office  
A home office is any location with a small number of stations, low data transfer  
needs, and limited expected expansion requirements. While most networks of this  
sort are located in homes or small family businesses, the “home office”  
description can also apply to small, minimal-growth departments within a state  
of the art enterprise network.  
Typically, home offices have no need of the advanced capabilities that are  
available in the more expensive, high-end networking devices, capabilities such  
as segmentation and switching, management, statistics tracking, or security.  
As home offices have such limited requirements, they quite frequently need  
nothing more complex than a single standalone device. This can mean a  
significant cost savings over other network implementations, such as modular  
chassis or even stackable hubs.  
The section which follows explains some of the decisions that must be made  
when approaching a design for a home office or similar small workgroup. This is  
followed by an example scenario which goes through these steps and displays  
one way of meeting the networking needs that are defined for that network.  
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Ethernet  
Abstracting the Design Process  
There are a series of logical stages that must be kept in mind when designing a  
network for any location, including the relatively simple home office. The first  
parts of the design process involve the decisions relating to the technology and  
media to be used in the workgroup. The complex nature of these questions can be  
intimidating to a new Network Designer, but the importance of good planning in  
these initial stages cannot be underestimated. A good decision can make a final  
design that is capable, flexible, and easy to implement, while a haphazard  
selection can lead to great difficulties in modifying the selected network  
organization to fit mismatched needs. The selection of a networking technology  
and the organization of stations into workgroups and enterprise networks is  
treated in detail in the Cabletron Networking Guide - MMAC-FNB Solutions.  
If the Ethernet networking technology is selected for a workgroup technology, a  
series of new decisions must be made to narrow that selection down to specific  
Cabletron Systems networking devices and a specific network implementation.  
Management  
The selection of a level of network management and control level is a primary  
selection criteria, and one that quickly divides Ethernet networking devices into  
compliant and non-compliant categories. Manageable, or “intelligent” devices,  
while more costly than non-intelligent devices, allow the control of ports and  
connections through software and the monitoring of network traffic and statistics.  
This port control and statistics monitoring can greatly ease the troubleshooting  
process when network problems are detected. The larger a network is, the more  
important management capabilities become.  
Media  
While the selection of a suitable networking media or cabling for the home office  
network is a task that should be undertaken at the initial stages of network  
planning, along with deciding upon a networking technology, it is important to  
know how flexible the design can be with respect to media. If the product that  
best fits 90% of the requirements is not available with the media connections that  
were planned on, is it possible that the media used could be changed rather than  
replacing the selected device? In some situations, this will be the case. In others,  
the existing or planned media cannot be replaced or substituted out.  
In most home office situations, the cabling to be used in the network will be  
jumper cabling, which either remains loose and exposed or is taped to the wall or  
floor. The media in home offices, therefore, is relatively easy to change, as long as  
all safety and distance limitations are met.  
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Ethernet  
Some Cabletron networking devices, through their support of PIMs and BRIMs,  
will support a small number of connections using different media. For example,  
an Ethernet network which is made up primarily of 10BASE-T links has a single  
multimode fiber optic connection to a distant building. If a standalone or  
stackable device which supports EPIMs is selected for the network in the main  
location, an EPIM-F2 can be added to the device, eliminating the need for an  
expensive external transceiver.  
Interconnection  
While most home offices are designed as islands of networking, not designed to  
be connected to other networks, instances may arise where a small, simple  
network requires a connection to a larger enterprise or facility network. In these  
situations, it is recommended that the Network Designer no longer consider the  
workgroup to be a home office, but design it in the same fashion as a small or  
remote office. Small and remote office network designs for Ethernet are discussed  
in detail in their respective sections later in this chapter.  
Expandability  
The importance of a smooth and simple path for adding users to the home office  
network is something that, while usually not a driving factor in the decision  
making process, should be considered.  
Port Count  
Once a decision has been reached on how essential management capabilities are  
for the home office workgroup, the Network Designer must ensure that the  
hardware selected will meet the required port count. If the selected device cannot  
support the required number of users, additional devices need to be added to the  
design or a complete redesign of the network needs to be undertaken. This  
redesign may involve breaking the network up into smaller workgroups or  
simply extending the Ethernet network to include more users.  
Price  
The price factor in any network design decision is a very important consideration.  
Every designer wants to provide the highest level of functionality and  
performance, including management, expansion, redundancy and fault tolerance.  
These features all come with a price tag, however. In every case, there is a budget  
or an allotted amount of funds to be considered. The specifics of pricing and  
expense are a matter for you to decide, as this guide cannot tell you how much  
money you have to invest.  
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Ethernet  
In an effort to provide some measure of differentiation between the varying levels  
of expense, the design tables which list a series of possible selections in a  
particular category attempt to organize the networking devices presented in  
ascending order of expense. In many cases, the difference between the list prices  
of some networking devices is quite small, so this arrangement of products  
should be considered an estimation aid only.  
Other Considerations  
In some cases, there are special design issues that restrict Network Designers to  
particular hardware selections. Limited available space, for example, or the  
environmental conditions of the install location may play a part in the selection of  
a networking device for the home office. These specialized considerations are  
beyond the scope of this document, but a large amount of information can be  
found in the Cabletron Systems Networking Solutions Product Guide.  
Design Example  
The example which follows traces the selection process of a new Network  
Designer attempting to design a network for a single-room home office, shown in  
of the proposed network, and has decided to use a single-segment Ethernet  
network. The network will need to support a small custom greeting card  
operation which consists of six stations - four production stations, one accounting  
station, and one administration station which acts as a server for the single office  
printer. The network will not support any on-line applications, server-heavy  
traffic, or email, and is intended only to make the exchange of files (currently  
done through passing floppy disks) easier.  
2094n13  
Figure 6-1. Home Office - Initial Scenario  
6-8  
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Ethernet  
The table below shows the selection field of Cabletron Systems shared Ethernet  
workgroup devices. This is the same table that was displayed at the beginning of  
this chapter. During the course of the design example, sections of the table shown  
will be removed to indicate the gradual reduction of choices as the needs of the  
network are compared to the capabilities of the devices.  
Max  
Management  
Product  
MR9T-E  
Type  
Media  
Port Count PIMs/BRIMs  
repeater  
stackable  
stackable  
stackable  
NONE  
NONE  
NONE  
NONE  
UTP  
UTP  
UTP  
8
1 EPIM  
1 EPIM  
2 EPIMs  
1 EPIM  
SEH-22/32  
SEH-24/34  
SEH-22FL  
12  
24  
12  
Multimode  
Fiber Optics  
SEHI-22/32  
SEHI-24/34  
SEHI-22FL  
stack base  
stack base  
stack base  
SNMP  
SNMP  
SNMP  
UTP  
UTP  
12  
24  
12  
1 EPIM  
2 EPIMs  
1 EPIM  
Multimode  
Fiber Optics  
MicroMMAC-22/32E  
MicroMMAC-24/34E  
stack base  
stack base  
RMON  
RMON  
UTP  
12  
24  
1 EPIM  
1 BRIM  
UTP  
2 EPIMs  
1 BRIM  
The Network Designer has decided that, due to the size and expected simplicity  
of the network, management is not a driving concern at this point in time. As cost  
is an issue, and management capabilities do add to the cost of networking  
devices, the Network Designer removes those intelligent devices from the  
selection field. The products removed from the field are not fully discarded from  
consideration, however. If the remaining non-intelligent devices do not provide a  
suitable match to the other needs of the network, the Network Designer can go  
back and examine these intelligent devices for their suitability.  
Ethernet Workgroup Design  
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Ethernet  
Max  
Management  
Product  
Type  
Media  
Port Count PIMs/BRIMs  
MR9T-E  
repeater  
stackable  
stackable  
stackable  
NONE  
NONE  
NONE  
NONE  
UTP  
UTP  
UTP  
8
1 EPIM  
1 EPIM  
2 EPIMs  
1 EPIM  
SEH-22/32  
SEH-24/34  
SEH-22FL  
12  
24  
12  
Multimode  
Fiber Optics  
The media selected for the network is inexpensive Category 3 UTP jumper  
cabling. The low cost, durability, and ready availability of UTP makes it by far the  
preferred media for this installation. If there were specific electrical noise or  
distance considerations, the Network Designer may have decided to attempt a  
design using multimode fiber optic cabling or other media. This media selection  
removes the SEH-22FL, a fiber optic device, from the selection field.  
As this is a small home office that does not plan to grow substantially, the ability  
to expand the network is not a primary concern. As there is no apparent need or  
desire to quickly and easily expand the network, the stackable products in the  
selection field are not required. Again, if later criteria prove that the remaining  
devices in the selection field do not measure up to the network’s needs, these can  
be reintroduced to the selection field.  
Max  
Management  
Product  
MR9T-E  
Type  
Media Port Count PIMs/BRIMs  
UTP 1 EPIM  
repeater  
NONE  
8
The easiest decision in the process of home office network design is the  
comparison of required port count (the number of stations that will be part of the  
network) and the port count supplied by the devices in the selection field. In the  
case of this example, the comparison indicates that the one remaining device in  
the selection field, the MR9T-E, provides three more 10BASE-T networking  
station ports than the network requires. The MR9T-E, therefore, meets all of the  
criteria judged to be important for this network.  
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The Network Designer checks the Cabletron Systems Networking Solutions Product  
Guide to examine the characteristics and full description of the MR9T. Deciding  
that the product will fit well into the installation, the Network Designer makes a  
call to the Cabletron Systems Sales Department and works out the details with a  
Sales Representative.  
MR9T  
2094n14  
Figure 6-2. Ethernet Home Office Implementation  
The Small Office  
A small office is a location that contains a greater number of stations than the  
typical home office, has greater throughput demands for the network, and has a  
much greater probability of expansion in the short term. The term “small office”  
in this section can also be applied to small, self-contained departmental networks  
within a larger facility or to departmental workgroups that are connected through  
their native networking technology to other portions of the corporate or facility  
network.  
Departments that are connected to a facility backbone which  
uses a different technology (e.g., FDDI) are considered remote  
NOTE  
offices, which are discussed later in this chapter.  
The small office, unlike the home office, often requires some of the advanced  
capabilities available in Cabletron Systems networking devices. Management and  
monitoring capabilities are frequently in the category of essential characteristics  
of small office hardware. The small office network is larger and more complex  
than the home office. Therefore, small office networks are more likely to benefit  
from the ability to quickly diagnose and correct problems, or foresee potential  
troubles through intelligent monitoring and examination of the network statistics  
collected by intelligent devices.  
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The small office location is an ideal place to examine the suitability of stackable  
networking devices. As these locations fall into a space between tiny workgroups  
and full-scale facility networks, they are the target location for stackables.  
The sections below describe the important criteria that need to be examined when  
selecting a networking solution for a small office location. In many cases, these  
criteria are exactly the same as those treated in the home office section discussed  
previously. The presentation of these network design criteria is followed by an  
example design, which supplies a small office situation and one solution to the  
needs of that proposed network.  
Abstracting the Design Process  
When designing a small office implementation, the Network Designer follows a  
decision making process that is essentially identical to that used for the design of  
a home office. The differentiation between the two procedures is found more in  
the responses to the issues raised by these criteria than by the actual criteria  
themselves.  
Management  
Management, again, adds control and monitoring functions to the networking  
devices. The benefits of management come at a cost of higher final product prices,  
and may not be fully recognized by extremely small or simplistic networks. The  
small office level is truly the middle ground between situations where  
management is essential and those where it is often not necessary.  
Media  
The type of media to be used in a small office network is an important  
consideration, as most of the network installations of comparable size involve  
facilities with existing cable or where an installation of new cabling is planned.  
This cabling is typically pulled through wall spaces and conduits, and is therefore  
more difficult to change in the event that the networking devices selected by the  
Network Designer do not match that cabling. Again, transceivers and media  
converters are available to make the change from one media to another, but are  
second-best solutions.  
Interconnection  
The small office, while often standing alone, may need a path of expansion or  
interconnection to later networks and workgroups. It is at these times that the  
interconnection options available in any networking device become important.  
Typically the interconnection devices that are most important from a network  
design point of view are those which provide connections to either different  
media of the same technology (PIMs) or to different networking technologies  
altogether (BRIMs).  
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Expandability  
The simplicity and fluidity of expansion in a small office setting is of paramount  
importance. Every small office wants to expand, even if it is an addition of  
nothing more than a few additional networked computers. The ability to quickly  
and efficiently increase the number of available ports in the small office network  
must factor into any selection of devices for installation. In these situations, the  
stackable products excel, providing for expansion of the number of available  
ports without risking any of the networking limitations of their technologies other  
than the maximums placed on the number of stations in a network.  
Port Count  
The port count decision for a small office network is a simple comparison of  
expected station counts with supplied port counts. As the port count range from  
the smallest intelligent standalone device to the largest, maximum size intelligent  
stack of stackable hubs covers from 13 to 120 ports, there should be sufficient port  
availability to cover the vast majority of small offices without requiring links to  
other stacks or devices.  
Price  
As always, the price factor must be considered in the network design process for  
small offices. While there may be a temptation to always opt for the lowest-priced  
device that meets the minimum requirements, Network Designers must keep in  
mind that expandability, manageability, and internetworking capabilities all come  
at an increase to final expense. Even if you do not think a BRIM slot will be  
needed for another two years, it is less expensive to purchase a device with BRIM  
capability and not use it than it is to have to replace the networking hardware at a  
later date to meet additional needs.  
Other Considerations  
In some cases, there are special design issues that restrict Network Designers to  
particular hardware selections. Limited available space, for example, or the  
environmental conditions of the install location may play a part in the selection of  
a networking device for the home office. These specialized considerations are  
beyond the scope of this document, but a large amount of information can be  
found in the Cabletron Systems Networking Solutions Product Guide.  
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Ethernet  
Design Example  
The following example follows a Network Designer’s selection process for a small  
office Ethernet network. As in the previous example, the Network Designer has  
already decided upon a networking technology (Ethernet) and a media type  
(10BASE-T) for the network.  
The location being considered is a combined warehouse and business office for a  
wholesale pottery distributor. The 27 users in the facility will be connected to one  
another through a single-segment Ethernet network. The Network Designer has  
verified that every cable that has been installed in the facility is in keeping with  
the tested characteristics of the 10BASE-T Ethernet standard. This network is  
being designed to support the new workstations and on-line order entry and  
inventory control system that the distributor is adopting.  
stations (21) located in the Business Office. The Business Office also contains three  
server stations, two for file storage and retrieval, and one for printing. The  
Loading Dock has ports for two stations, one of which will be used initially, and  
the Warehouse Floor has two stations for inventory tracking.  
Loading Dock  
Shipping 1  
Inventory Control 1  
Shipping 2  
(future)  
Office  
Stations  
(21)  
Warehouse  
Servers (3)  
Inventory Control 2  
2094n15  
Business  
Office  
Figure 6-3. Small Office - Initial Scenario  
The Network Designer examines the available field of networking devices for a  
single segment Ethernet network and decides that, due to the small size of the  
network, management capabilities are important, but are not the focus of the  
network. If there is a problem, the Network Designer will be able to use the  
management and control capabilities of the intelligent devices to assist in  
reducing the time needed to troubleshoot and resolve any service failures. The  
non-intelligent devices, such as the MR9T and the SEH stackable hubs are  
removed from the list of available choices.  
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Table 6-3. Shared Ethernet Workgroup Devices  
Max  
Management  
Product  
SEHI-22/32  
Type  
Media  
Port Count PIMs/BRIMs  
stack base  
stack base  
stack base  
SNMP  
SNMP  
SNMP  
UTP  
UTP  
12  
24  
12  
1 EPIM  
2 EPIMs  
1 EPIM  
SEHI-24/34  
SEHI-22FL  
Multimode  
Fiber Optics  
MicroMMAC-22/32E  
MicroMMAC-24/34E  
stack base  
stack base  
RMON  
RMON  
UTP  
12  
24  
1 EPIM  
1 BRIM  
UTP  
2 EPIMs  
1 BRIM  
As the network will be using UTP cabling, the SEHI-22FL can be removed from  
the selection field.  
Since growth is expected to be minimal, the Network Designer turns to examine  
the products that can be used in standalone mode. Considering the remaining  
field of devices, this reduces the choices available to the SEHI-22/32 and  
SEHI-24/34. Both of these devices are designed to be the base of a stack of  
stackable hubs. Recall that stackable products can all function without being part  
of a stack, a capability which has greatly reduced the list of Ethernet products that  
are standalone repeaters only.  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
SEHI-22/32  
SEHI-24/34  
stack base  
stack base  
SNMP  
SNMP  
UTP  
UTP  
12  
24  
1 EPIM  
2 EPIMs  
When comparing the port count of the SEHI-24/34, which has the highest port  
count, to the total station count of the proposed network, the Network Designer  
notices that the SEHI-24 alone does not meet the total required number of stations  
(27). While it would be possible to purchase a second SEHI device to handle the  
remaining stations and provide a jumper cable to link the two devices together,  
the Network Designer can link a stackable product, the SEH-22, to the SEHI-24  
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through an interconnect cable and have a stack providing 36 ports. This entire  
stack will act as a single repeater, and the management functions that are included  
in the SEHI-24 will be applied also to the SEH-22 in the stack.  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
SEHI-24/34  
SEH-22/32  
stack base  
stackable  
SNMP  
NONE  
UTP  
UTP  
24  
12  
2 EPIMs  
1 EPIM  
Loading Dock  
Inventory Control 1  
Shipping 1  
Shipping 2  
(future)  
Office  
Stations  
(21)  
Warehouse  
SEH-24  
SEHI-24  
Servers (3)  
Inventory Control 2  
2094n16  
Business  
Office  
Figure 6-4. Ethernet Small Office Implementation  
The Remote Office  
The remote office installation is a special case of the small office scenario treated  
in the previous section. The differentiation between the small office and the  
remote office is that the remote office requires a connection to a different  
networking technology in order to make a connection to a larger or physically  
separate network. In the classical sense, this refers to a branch office location that  
has a Wide Area Networking link to the parent company network.  
The vast majority of “remote offices” are actually individual workgroups in a  
larger facility that are all connected to one another through a high-speed  
backbone technology such as FDDI.  
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FDDI  
Backbone  
2094n17  
Figure 6-5. FDDI Backbone Internetworking  
The main difference between the small office and the remote office is that a  
provision must be made to accommodate a connection to a different networking  
technology. In the case of Cabletron Systems workgroup products, this process  
has been simplified by the inclusion of BRIM capabilities into the MicroMMAC  
stackable bases and the ESX and NBR Ethernet switches.  
Essentially, the design process for the remote office is the same as that for the  
small office as discussed previously. The remote office requires an additional  
series of steps related to the use of BRIMs. Once the localized workgroup portions  
of the network have been finalized, the BRIM selection process can begin.  
BRIM Selection  
As most remote office environments will deal with BRIM-capable standalone or  
stackable devices, the selection of the correct BRIM is an essential portion of the  
network design. There are several BRIM models available for a number of  
different internetworking needs. These BRIM types are listed in Table 4-2, found  
in Chapter 4, PIMs and BRIMs.  
For fully up-to-date information regarding BRIM interoperability, contact your  
Cabletron Systems Sales Representative with specific questions.  
PIM Selection  
Several BRIMs require PIMs in order that they support connections to the proper  
networking media. The type of PIM that must be specified is dependent upon the  
type of BRIM that is being customized. BRIMs with FDDI connections require  
FPIMs, BRIMs with Ethernet connections require EPIMs, and so on.  
Table 4-1, found in Chapter 4, provides the vital information regarding all  
available PIMs.  
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Design Example  
For an example of remote office workgroup configuration, we will build upon the  
previous small office example. Let us assume that there has been no growth of the  
small office network, but the pottery distributor has been purchased by a larger,  
nationwide chain of distributors. The facility itself will not be changing  
appreciably, but the facility will need a Wide Area Network connection to the  
regional headquarters in a neighboring state. The regional office makes  
connections to the remote distributors with 56K WAN links in order to keep  
running, constantly-updated inventory and accounting records.  
When comparing the available methods of connecting to the WAN, the Network  
Designer determines that a Cabletron Systems BRIM, the BRIM-W6, is capable of  
handling 56K WAN traffic. The networking hardware is still handling network  
traffic in the facility properly, so there is no need to upgrade the network itself,  
but the SEHI-24 that is the base of the stack will not support a BRIM.  
Looking back at the selection chart, the Network Designer notices that the  
MicroMMAC-24E, another device that can act as a stackable base, supports one  
BRIM connection. In order to be certain that the network that is being considered  
will work, the Network Designer consults the table of BRIM interoperability and  
determines that the BRIM-W6 will, in fact, work properly in the  
MicroMMAC-24E.  
The new design requires the replacement of the SEHI-24 with a MicroMMAC-24E  
containing a BRIM-W6. The stackable hub previously controlled by the SEHI-24  
will remain, and will be connected to the MicroMMAC-24E through the HubStack  
Interconnect Cables.  
Intelligent stackable devices cannot be placed in a stack with  
other intelligent stackable devices. The intelligent devices do  
NOTE  
not have IN ports for HubStack Interconnect cables.  
The SEHI-24 can then be placed in storage, ready to be swapped in should there  
be a problem with the MicroMMAC that requires it be sent back to Cabletron  
Systems for service. This arrangement of on-site spares can greatly reduce the  
amount of downtime, or non-operation, that a network experiences.  
The BRIM-W6 in the MicroMMAC-24E requires further configuration to work  
with the 56K link. The BRIM-W6, in order to provide the greatest flexibility to  
consumers, uses specialized PIMs for connection to different WAN types. These  
Wide Area Network Port Interface Modules, or WPIMs, are listed in the PIMs  
table, Table 4-1. Examining the table to see which WPIM matches the needs of the  
facility, the Network Designer chooses the WPIM-DDS. The resulting network  
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Office  
Stations  
(21)  
SEH-24  
To Main Office  
MicroMMAC-24  
with BRIM-W6  
Servers (3)  
Business  
Office  
WAN (56K)  
2094n18  
Figure 6-6. Ethernet Remote Office Implementation  
The High-End Department  
The high-end department is a workgroup with specialized needs, demanding  
high reliability or high throughput to each and every station. The high-end  
department typically consists of the most demanding users on the network, and  
connections between them must be fast, reliable, and predictable.  
One of the ways to supply predictability and speed to users in the high-end  
workgroup is through per-port switching. In a switched Ethernet workgroup, an  
Ethernet switch provides dedicated 10 Mbps Ethernet links to each and every  
user. This means that there will always be an available, full-speed Ethernet link  
that may be set up between any two Ethernet stations in the high-end workgroup.  
The use of switched connections in an Ethernet environment provides an added  
benefit to stations requiring high throughput. Since each Ethernet link is  
dedicated, and will receive traffic from no other sources than the station and the  
switch, if the network is within the allotted limitations, the Ethernet link can  
operate in full-duplex mode. This method of operation allows a station or switch  
to transmit data on one portion of the Ethernet link while simultaneously  
receiving data on the other portion of the link. This concurrent transmission and  
reception effectively doubles the throughput of the Ethernet link, from 10 to  
20 Mbps.  
Abstracting the Design Process  
The design of a high-end department’s workgroup solution is a highly  
customized procedure. The organization of the workgroup determines the  
distribution and provision of switched ports and switched uplinks. The decisions  
to be made are similar to those dealt with in other design strategies, but the  
demanding nature of the high-end department tends to influence the decisions  
toward greater control and higher functionality.  
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Management  
In a network using any form of segmentation, whether it is bridging, switching,  
or routing, management functionality is a part of the devices needed to create the  
network. Without some form of management, segmentation decisions can not be  
made by the devices. The level of management available in any segmentation  
situation is the differentiation between products. Again, the decision of what level  
of management functionality a particular installation requires is a matter for the  
Network Designer to decide on an individual basis.  
Expandability  
Switches are not noted for their fluid expansion path. It is not possible to add  
switches to another switch in order to make a stack. Any time a high-end  
workgroup needs to expand, it will have to make a switched connection between  
switches. Often this is accomplished with a simple jumper cable, from a front  
panel port of one switch to a front panel port of another. In these situations, it is  
important to remember that Ethernet treats switches like bridges, and imposes a  
bridge rule upon any Ethernet network: no more than eight segments and seven  
bridges in the longest signal path. Since this bridge rule can severely limit the  
magnitude of networks incorporating per-port switching on a large scale, the  
expansion of high-end workgroups is often accomplished through the  
interconnection of several switches through a faster, larger-scale networking  
technology.  
Interconnection  
As mentioned above, many times the interconnection of switches for a high-end  
department will be accomplished through the use of a higher-speed technology,  
such as FDDI. In these situations, the BRIM support of some Cabletron Systems  
standalone switching products can be very useful, saving the Network Designer  
the cost of a separate standalone Ethernet to FDDI bridge or router.  
Port Count  
The examination of port count, as before, is a simple comparison of requirements  
to availability. If a device does not meet the port count requirements of the  
workgroup, additional devices may have to be added to the design.  
Price  
As switches incorporate additional decision-making logic and memory for the  
performance of their functions, switches, as a rule, are more expensive than  
simple repeaters. The per-port cost may be greater than that of a stackable hub,  
but the functionality provided by each port is also much greater. When designing  
a high-end workgroup, keep the price levels that will be involved in mind.  
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Design Example  
As an example, we can examine a network design that is being planned for a  
group of Computer-Aided Design (CAD) engineers in a large architectural firm.  
These CAD designers want to replace their existing shared Ethernet LAN with a  
network that provides greater throughput between their end stations. The  
Network Designer, who is already familiar with Ethernet networking, does not  
wish to change the technology that the group uses, and has decided that a simple  
and cost-effective way to provide more bandwidth to each end station is through  
per-port switched Ethernet connections.  
The CAD department consists of 16 CAD designers, 2 CAD image file servers,  
and 3 plotters, all in a single facility. The stations have existing 10BASE-T links to  
the wiring closet. The CAD department is currently linked to the rest of the  
company through an Ethernet connection to a bridge in the Materials Research  
department. The Network Designer, hoping to simplify the network, wants to  
connect the CAD group directly to the corporate backbone, an FDDI ring.  
Materials  
Research  
CAD Stations (16)  
Plotters (3)  
repeater  
repeater  
bridge  
Image Servers (2)  
2094n19  
FDDI Backbone  
Figure 6-7. High-End Department - Initial Scenario  
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Ethernet  
The Network Designer is looking for one or more per-port Ethernet switches that  
can be used to make network connections to the stations in the CAD department.  
The Network Designer examines the selection field of Ethernet switches, shown  
in Table 6-2. All of these devices meet the initial criteria; they are manageable  
Ethernet switches with similar expansion capabilities. Because of the Network  
Designer’s intent to connect the Ethernet switches directly to the corporate FDDI  
backbone, the products that do not support BRIM connections are eliminated  
from consideration. This leaves the selection field shown below.  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
NBR-620  
SNMP  
0
6
4 EPIMs  
2 BRIMs  
ESX-1320  
ESX-1380  
RMON  
RMON  
UTP  
12  
12  
13  
13  
1 BRIM  
1 BRIM  
Multimode  
Fiber Optics  
The Network Designer then moves on to examining the port count and media  
type of the remaining devices. The NBR-620 is immediately removed from  
consideration due to the low port count it provides. In order to meet the needs of  
the network, the Network Designer would have to configure 6 NBR-620 Ethernet  
switches, each of which would have to contain four EPIMs for 10BASE-T  
connections and one BRIM for a connection to the FDDI backbone. As such a  
solution would cost more than comparable solutions, without providing a  
significant benefit over those solutions, the NBR-620 is removed from  
consideration.  
This leaves the selection field with the ESX-1320 and ESX-1380, two Ethernet  
switches that support RMON management, one BRIM connection, and 12 switch  
interfaces. The port count requirements are not met by either device alone,  
however. The Network Designer refers back to the full selection field, looking for  
a device that will support all 21 of the stations in the workgroup.  
The device that is capable of supporting 24 switched Ethernet connections, the  
FN10, has already been removed from consideration, but it is re-introduced due  
to its higher port count. The Network Designer takes a second look at the  
capabilities of the FN10 in comparison to those of the ESX-1320 and ESX-1380.  
Deciding that the BRIM capability and advanced network management of the  
ESX-1320 and ESX-1380 outweigh the higher port count of the FN10, the Network  
Designer again removes it from consideration and continues.  
The Network Designer than examines the media that are supported by the two  
devices still under examination. The ESX-1380 supports 12 multimode fiber optic  
connections, while the ESX-1320 supports unshielded twisted pair cabling.  
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The Network Designer selects the ESX-1320 and calculates that two ESX-1320  
switches, each containing one BRIM module for an FDDI connection, will meet  
the needs of the CAD department. The Network Designer would then go on to  
select the correct BRIMs and any necessary PIMs for these switches.  
Referring to the BRIM chart, the Network Designer finds that the BRIM-F6 is the  
BRIM that is needed. This FDDI BRIM requires two FDDI Port Interface Modules,  
or FPIMs. Matching the media type of the corporate backbone to the media types  
of the FPIMs, the Network Designer selects four FPIM-00 modules, two for each  
BRIM.  
The resulting network, when installed, will resemble that shown in Figure 6-8,  
below.  
Materials  
Research  
CAD Stations (16)  
Plotters (3)  
ESX-1320 containing BRIM-F6  
Image Servers (2)  
repeater  
bridge  
2094n20  
FDDI Backbone  
Figure 6-8. Ethernet High-End Department Implementation  
Ethernet Workgroup Design  
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Ethernet  
Permutations  
It is also possible to use an Ethernet switch to connect a series of individual  
workgroups, rather than workstations or other devices. In these situations, the  
Ethernet switch acts as a device collapsed backbone for the network. The design  
process is exactly the same as that used to connect multiple workstations over an  
Ethernet switch, but the connections are made to workgroups rather than  
individual stations.  
Design Example  
Our example situation for the interconnection of workgroups through a  
standalone Ethernet switch involves a planned device collapsed backbone. This  
backbone will be implemented in a small vocational college which plans to  
interconnect its Ethernet classrooms and laboratories. The classrooms and labs are  
configured with Ethernet stackable hubs. There are four classrooms and two labs  
to be connected to the backbone, and there is expected to be growth in the number  
of Ethernet workgroups at the college in the future. The connections from the  
classrooms to the switch (which will be located in one of the labs) will have to be  
made through an aerial cable between buildings. Since conductive cable run  
between buildings is a lightning hazard, multimode fiber optics will be used to  
connect to each stack.  
The Network Designer examines the available Ethernet switches for a product  
with sufficient management, port count, media, and interface characteristics. The  
only Ethernet switch in the selection field that provides native multimode fiber  
optic media support is the ESX-1380, which provides sufficient numbers of ports  
and the availability of a BRIM port for future migration to new networking  
technologies. The Network Designer plans on using the ESX-1380 and orders six  
EPIM-F2s which will provide multimode fiber optic connections at each of the six  
remote workgroups.  
6-24  
Ethernet Workgroup Design  
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Chapter 7  
Fast Ethernet  
This chapter examines the decisions and selections that must be made when designing a Fast  
Ethernet workgroup solution.  
Should a Fast Ethernet workgroup solution be selected, the Network Designer has  
a specific series of issues to resolve and decisions to make before selecting a Fast  
Ethernet device that meets the requirements of the network. This chapter  
identifies and discusses these issues and provides a series of examples for  
different Fast Ethernet network approaches.  
Fast Ethernet Workgroup Devices  
The following sections present and describe the various Cabletron Systems  
workgroup networking devices that may be used to implement a Fast Ethernet  
networking solution.  
Shared Devices  
The selection field of Fast Ethernet networking devices is much narrower than  
that available for Ethernet workgroups. The Fast Ethernet devices available from  
Cabletron Systems are all 100BASE-TX compliant Class I repeaters or switches.  
The currently-available Class I repeaters, which are shared Fast Ethernet devices,  
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Fast Ethernet  
Table 7-1. Shared Fast Ethernet Workgroup Devices  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
a
SEH100TX-22  
SEHI100TX-22  
stackable  
stack base  
NONE  
UTP  
UTP  
22  
22  
1 EPIM  
SNMP  
2 EPIMs  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
The columns in the table provide the same information that Table 6-1 provides  
regarding Ethernet devices.  
Switched Devices  
Cabletron Systems produces one Fast Ethernet switching device, the FN100. The  
capabilities of the FN100, and the differing types of FN100 available are displayed  
Table 7-2. Fast Ethernet Workgroup Switches  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
FN100-8TX  
FN100-16TX  
SNMP  
SNMP  
UTP  
UTP  
8
8
0
0
16  
16  
Multimode  
Fiber Optics  
FN100-8FX  
SNMP  
SNMP  
8
8
0
0
Multimode  
Fiber Optics  
FN100-16FX  
16  
16  
Again, the columns of the table provide the same information that is supplied by  
Table 6-2 for Ethernet switching devices.  
7-2  
Fast Ethernet Workgroup Devices  
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Fast Ethernet  
Fast Ethernet Workgroup Design  
The network design process for Fast Ethernet workgroups is nearly identical to  
that used for standard Ethernet workgroups. The Network Designer must first  
break the network up into workgroups, if desired, determine how the stations in  
each workgroup will relate to one another, and then begin the process of selecting  
hardware. The types of hardware considered will be dependent upon the type of  
network installation that the workgroup is being designed for.  
The following sections break the process of Fast Ethernet network design up into  
treatments of three different types of situations: those requiring a relatively large  
number of users (the small office), those requiring high per-port throughput (the  
high-end department), and those situations where several workgroups are being  
interconnected (Fast Ethernet as a backbone).  
While these situations do not cover every possible Fast Ethernet implementation,  
it is a relatively simple task to use the closest approach to the particular needs of  
the proposed workgroup as a template for design.  
Small Offices  
The term “small office” as it applies to Fast Ethernet installations using Cabletron  
Systems workgroup devices, can be misleading. This workgroup archetype  
simply refers to the workgroup as a single segment with no special  
internetworking needs (no uplinks to different WAN or backbone technologies).  
The small office, in the case of the design strategy outlined below, can include  
anywhere from two to 120 Fast Ethernet stations.  
Abstracting the Design Process  
As the number of potential devices to select from in a Fast Ethernet network  
design is quite small, the actual design process for workgroup networks is highly  
simplified. The Network Designer needs only to determine what level of  
management is required within the workgroup and calculate the number of ports  
that will be needed to support the users at that location.  
Management Requirements  
As there are only two choices for shared segment Fast Ethernet devices, the  
selection of management functionality becomes a “yes or no” decision. The  
control and troubleshooting ease supplied by management capabilities is often of  
greater value in the complex and high-performance Fast Ethernet networks than  
the cost reduction realized by foregoing management altogether.  
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Fast Ethernet  
Port Count  
The first device in the stack, whether an intelligent SEHI100TX-22 or  
non-intelligent SEH100TX-22, will provide connections for up to 22 Fast Ethernet  
stations. For every additional 22 Fast Ethernet stations or fraction thereof, the  
Network Designer must add one SEH100TX-22 to the stack.  
The maximum number of ports that can be supported in this fashion is 110. In  
order to support more connections, the user-configurable EPIM slots on the  
SEHI100TX-22 and SEH100TX-22 will have to be used. If the EPIM slots are all  
used, the Fast Ethernet stack will reach its limitation of 119 users. Any Fast  
Ethernet workgroup containing more than 119 stations will require the creation of  
another workgroup to support the full user count.  
Design Example  
A travel agency sales department is looking to replace its current Ethernet  
network with a Fast Ethernet network in order to gain higher throughput and  
faster access to shared resources such as the two departmental file servers and the  
order entry system. The department also plans to add twenty sales  
representatives to the current network in the coming fiscal quarter.  
Order Entry  
Servers (2)  
repeater  
repeater  
Stations (40)  
2094n21  
Figure 7-1. Small Office Network - Current Status  
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Fast Ethernet  
The current network consists of 43 stations, including the shared servers and  
order entry system. The department currently operates on two standalone 24-port  
Ethernet repeaters that are connected to one another with a single jumper cable.  
All stations in the network are connected to these standalone repeaters with  
Category 5 UTP cable. All of the distances and network radii have been calculated  
to be within the acceptable limits for a Fast Ethernet network using a Class I  
repeater.  
The Network Designer, looking over the available Fast Ethernet networking  
devices, has only a few decisions to make to select a product or series of products  
for the installation. The Network Designer decides not to pursue a switched Fast  
Ethernet network implementation, due to the perceived higher cost of such a  
solution.  
The Network Designer then turns to the question of management. Understanding  
the value of management functions to a network of this scale and complexity, the  
Network Designer intends to incorporate management into the workgroup to aid  
in diagnosing problems and controlling the network. Examining the selection  
filed, the Network Designer selects the SEHI100TX-22, which provides SNMP  
management functions. As the SEHI100TX-22 is a stack base, any non-intelligent  
SEH100TX-22 hubs that are connected to the SEHI100TX-22 with HubSTACK  
Interconnect Cables will also become a manageable device.  
As it has already been established that the proposed network plans to add not less  
than 20 users in the upcoming quarter, it stands to reason that the network will  
expand even more in the future. This expansion can be managed quite easily by  
the SEHI100TX-22 stackable base. Any time that the number of station  
connections required by the network exceeds that provided by the Fast Ethernet  
stack, an additional SEH100TX-22 non-intelligent stackable hub can be added to  
the stack, providing an additional 22 ports.  
The Network Designer then double-checks the available port count of the  
SEHI100TX-22. While the SEHI100TX-22 can support only 22 of the 43 required  
connections, the device is designed to act as a stack base. By adding one  
SEH100TX-22 to the stack, the Network Designer expands the port capacity of this  
Fast Ethernet repeater domain to 44 users. When the next 20 users are added in  
the upcoming fiscal quarter, another SEH100TX-22 can be placed in the stack,  
bringing the total number of ports supported up to 66.  
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Fast Ethernet  
This expansion can continue until the stack contains five devices, the maximum  
number allowable with the stackable hub design. At this limitation, the stack will  
be capable of supporting up to 110 Fast Ethernet users.  
Order Entry  
Servers (2)  
(future)  
SEH100TX-22  
TX  
TX  
Stations (40)  
SEHI100TX-22  
2094n22  
Figure 7-2. Fast Ethernet Small Office Implementation  
High-End Department  
As previously seen in the design approach to small office implementations of Fast  
Ethernet, the design approach and decisions required of high-end departments  
using the Fast Ethernet technology do not differ much from those used for normal  
Ethernet designs. In the same fashion, the definition of a Fast Ethernet high-end  
department is identical to that of a standard Ethernet high-end department.  
The high-end department is a workgroup that has a number of closely associated  
stations or users, each having very demanding network needs. These stations  
often require the special functions provided by switching: dedicated links, high  
throughput, and full-duplex operation.  
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Fast Ethernet  
Abstracting the Design Process  
device, the amount of decision-making remaining in the design process after the  
decision to use the Fast Ethernet technology is minimal. Due to the fact that the  
FN100-TX series is available with either eight or 16 switch interfaces and front  
panel ports that use either UTP or multimode fiber optic media, there are a few  
design issues left where decisions have to be made.  
Media  
To date, there are two media options available for Fast Ethernet networks: UTP  
and multimode fiber optics. The selection of a particular media for a Fast Ethernet  
network implementation must be accomplished before any hardware selection  
has been done. This is so the network radius and segment length calculations may  
be made and checked against the allowable maximums of the Fast Ethernet  
technology.  
Port Count  
As Fast Ethernet switches are not as easily expanded to accommodate new  
connections as stackable hubs are, it may be wise when designing a Fast Ethernet  
workgroup to provide extra connections. This kind of forethought can save the  
cost of purchasing another standalone device to provide network access to just  
one more station in the future.  
Design Example  
As an example of a high-end department implementing a Fast Ethernet network  
solution, let us examine a university mathematics lab consisting of 14  
high-performance workstations which handle complex calculations and perform  
a variety of networked applications, including imaging, estimation, and series  
sorting. All of these stations are to be configured to connect to the Fast Ethernet  
network using Category 5 UTP cabling.  
All of the stations in the laboratory have been determined to lie well within the  
maximum network radius of a Fast Ethernet network. The Network Designer  
plans to use switched Fast Ethernet as a networking technology, and intends to  
connect this workgroup to the campus network through a fiber optic Fast  
Ethernet connection to the facility hub, which handles all connections to the  
campus backbone network.  
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Fast Ethernet  
The Network Designer begins the design process by examining the available Fast  
Ethernet switch products. As the only devices available offering per-port Fast  
Ethernet switching are the four types of FN100 standalone switch, the selection  
field is very narrow, consisting of the products shown in the table below.  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
FN100-8TX  
FN100-16TX  
SNMP  
SNMP  
UTP  
UTP  
8
8
0
0
16  
16  
Multimode  
Fiber Optics  
FN100-8FX  
SNMP  
SNMP  
8
8
0
0
Multimode  
Fiber Optics  
FN100-16FX  
16  
16  
Due to the extremely limited selection field, the Network Designer can only select  
one of the two FN100 models or attempt to use a different solution for this  
workgroup, perhaps selecting a modular chassis-based solution.  
The FN100-16TX meets the required port count of 14. As there are no other  
options available from which to choose a compliant device for this network  
implementation, the Network Designer examines the Cabletron Systems  
Networking Solutions Product Guide to determine the fitness of the FN100-16TX for  
this particular situation.  
Examining the Cabletron Systems Networking Solutions Product Guide, the Network  
Designer discovers that the FN100-16TX, which had been selected, provides two  
100BASE-FX connections that may be activated in the place of two of the  
100BASE-TX connections. By disabling one of the UTP connections, the Network  
Designer can make the desired multimode fiber optic link to the facility hub  
without requiring an external transceiver. The resulting network looks like  
7-8  
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Fast Ethernet  
Stations (14)  
Facility Hub  
FN100-16TX  
2094n23  
Figure 7-3. Fast Ethernet High-End Department Solution  
Fast Ethernet as a Backbone  
Due to the high throughput provided by Fast Ethernet, it is conceivable that the  
technology could be used as a backbone solution to interconnect a series of  
workgroups. The Fast Ethernet switch will act as a device collapsed backbone for  
the network. The design process is exactly the same as that depicted above, in  
which connections were designed between multiple workstations over a Fast  
Ethernet switch, but the connections in the backbone solution are made to  
workgroups rather than individual stations.  
Due to the short maximum distances of Fast Ethernet  
segments, Fast Ethernet is sometimes unsuitable for  
NOTE  
interconnecting workgroups in a widely-dispersed enterprise  
network.  
Design Example  
As an example of the methods used to design a switched Fast Ethernet backbone  
network, let us examine the design process of a Network Designer at a small  
magazine publishing house who intended to replace the existing Ethernet  
device collapsed backbone using switched Fast Ethernet.  
Fast Ethernet Workgroup Design  
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Fast Ethernet  
StockPhoto  
Archive1 Archive2  
2094n24  
Figure 7-4. Initial Network Design  
Each departmental stack consists of one MicroMMAC-24E and one or more  
SEH-24 stackable hubs. In the initial configuration, the MicroMMAC-24Es have  
been configured with EPIM-A modules, which provide AUI ports for connection  
to a standard Ethernet AUI cable. These AUI cables are then connected to thick  
coaxial cable transceivers that are connected to the coaxial cable backbone.  
This arrangement is currently suffering from slow network response times and  
poor throughput during normal working hours. The thick coaxial cable backbone  
is also quite difficult to monitor for errors, and any failures or performance losses  
are exceedingly difficult to troubleshoot.  
Access to the three shared file servers (Archive1, Archive2, and StockPhoto) is  
required by all departments, and users have been complaining about the length of  
time necessary to place and retrieve files using these servers.  
The Network Designer has already examined the distances involved in the  
facility, and has determined that the Fast Ethernet network implementation will  
need to use multimode fiber optics as a connection media in order to properly  
manage the distances involved in the network.  
As all of the devices in the selection field have similar operational qualities with  
regard to management, expandability, interconnection, and price, the only  
decisions that need to be made for the selection of a central Fast Ethernet switch  
are those of media and port count.  
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Fast Ethernet  
The Network Designer examines the four types of FN100 Fast Ethernet switch,  
looking to see which models support front panel multimode fiber optic  
connections. The FN100-8FX and FN100-16FX both provide multimode fiber optic  
connections for 100BASE-FX network media, and thus both meet the  
requirements of this site.  
The Network Designer then examines the port count supported by each device,  
and finds that both devices will fill the required network link count of six. The  
Network Designer decides, however, to optimize the access of the workgroups to  
the three shared fileservers by giving each fileserver a dedicated link to the  
switch  
Servers  
(100 Mbps)  
Workgroups  
(10 Mbps)  
2094n25  
Figure 7-5. Shared Server Optimizations  
These switched station connections will provide full Fast Ethernet speed  
connections to each of the fileservers. While this will introduce a switch into the  
path from any station to any server, this will offer better throughput from a  
network-wide point of view than leaving the servers on their current shared  
segments. As no end user station can access the network at a speed greater than  
the 10 Mbps provided by the shared Ethernet segments, each fileserver can  
theoretically handle requests from all six workgroups simultaneously without  
suffering a reduction in throughput to the Fast Ethernet switch.  
This optimization of the shared resources of the fileservers will cause the required  
number of connections to exceed the number supplied by the FN100-8FX. The  
network implementation, therefore, will require the FN100-16FX, which provides  
16 multimode fiber optic connections.  
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Fast Ethernet  
Once the backbone switch has been selected, changes need to be made to the  
workgroups that will connect to the switch itself. As they stand, the current  
workgroups cannot connect to the Fast Ethernet backbone network. In order to  
support Fast Ethernet connections to the FN100-16FX, the MicroMMACs will  
require a BRIM. The Network Designer examines the available BRIMs that can be  
placed in the MicroMMAC-24Es. The BRIM-E100, when configured with the  
proper Fast Ethernet Interface Modules, will provide a Fast Ethernet uplink to the  
MicroMMAC-24Es. In order to support multimode fiber optic cabling, each of the  
six BRIM-E100s will be configured with two Fast Ethernet Interface  
Module-100FXs, providing 100BASE-FX connections. Once installed, the network  
StockPhoto  
FN100-16FX  
Archive1 Archive2  
2094n26  
Figure 7-6. Fast Ethernet Backbone Implementation  
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Chapter 8  
Token Ring  
This chapter examines the decisions and selections that must be made when designing a Token Ring  
workgroup solution.  
The process of designing a Token Ring workgroup or a series of interconnected  
workgroups is somewhat different from the processes involved in designing an  
Ethernet or Fast Ethernet workgroup. The Token Ring networking technology  
places very strict limitations on several aspects of network design, and treats  
individual stations in a different manner than the other technologies treated in  
this document.  
Token Ring Workgroup Devices  
The following sections present and describe the various Cabletron Systems  
workgroup networking devices that may be used to implement a Token Ring  
networking solution.  
Shared Devices  
The vast majority of Token Ring networking devices available from Cabletron  
Systems are differing types of concentrators. The distinctions between the  
available devices are more differences of magnitude rather than of presence.  
While almost all the Token Ring devices that Cabletron Systems manufactures  
have some management capabilities, the Network Designer can choose the level  
of management incorporated on the devices.  
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Token Ring  
The available devices and the main distinctions between them are summarized in  
Table 8-1. Token Ring Workgroup Devices  
Max  
Management  
Product  
STH-22/24  
Type  
Media Port Count PIMs/BRIMs  
a
stackable  
stackable  
stack base  
stack base  
NONE  
UTP  
STP  
UTP  
STP  
12/24  
12/24  
12/24  
12/24  
2 TPIM  
2 TPIM  
2 TPIM  
2 TPIM  
a
STH-42/44  
STHI-22/24  
STHI-42/44  
NONE  
SNMP  
SNMP  
2 TPIM  
1 BRIM  
MicroMMAC-22T/24T stack base  
MicroMMAC-42T/44T stack base  
RMON  
RMON  
UTP  
STP  
12/24  
12/24  
2 TPIM  
1 BRIM  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
The columns in the table provide the same information that Table 6-1 provides  
regarding Ethernet devices. The Port Count field, again, is independent of the  
PIMs/BRIMs field.  
8-2  
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Token Ring  
Token Ring Workgroup Design  
Once a Network Designer understands the fundamentals of Token Ring design,  
as described in the Cabletron Systems Networking Guide - MMAC-FNB Solutions, the  
design of a Token Ring workgroup using standalone and stackable products is  
quite simple. If the limitations imposed by the standard are not exceeded, the  
Network Manager needs only to supply the required port count and management  
functionality, allowing room for future expansion and ensuring sufficient  
connections for any ring extensions or special media links.  
Small Office  
A small office design for a Token Ring network using standalone or stackable  
devices has two main defining characteristics. A small office Token Ring connects  
a number of users within one facility or campus that have no special  
internetworking needs or exceptional performance requirements. Small office  
Token Ring networks also must have an expected station count within the  
maximum number allowed on a single Token Ring at the desired network speed  
and using the intended media. Chapter 2, Review of Networking, provides a  
table summarizing these maximums.  
Abstracting the Design Process  
The procedures and decisions involved in designing a Token Ring network are  
quite straightforward and simple. Once it has been established that all the station  
cabling is within the allotted distances and the station count does not exceed the  
Token Ring maximums, the remainder of the design process is a simple provision  
of management functionality, sufficient ports, and support for any special  
connections.  
Management Requirements  
The importance of management capabilities in a Token Ring network is an  
extremely important consideration in the design process. The complexity of a  
Token Ring network can make unmanaged Token Ring networks extremely  
difficult to install and set up, and can greatly extend the time needed to  
troubleshoot network problems without management functions. As management  
in a well-run network is a paramount concern, Cabletron Systems Token Ring  
standalone and stackable devices are all manageable devices.  
The STH series of stackable hubs is one type of Token Ring device that contains no  
management functionality of its own, but it can be managed by an intelligent  
stackable base product such as the STHI. The decision to incorporate or forego  
management, including what level of management is desired, is a decision that  
must be based on the Network Designer’s level of skill with management and the  
perceived benefits to be gained from it.  
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Token Ring  
Media  
It is assumed by this document that the selection of a networking media for the  
facility has already been completed before the hardware is examined. The media  
decision in the hardware selection stage of network design is one of ensuring that  
the selected device or devices will support the cabling media that is either  
planned or in place.  
In some cases, a small number of station connections will have to be made using a  
less common media such as fiber optic cable. For these situations, Cabletron  
Systems produces a wide variety of media converters, which act as transceivers,  
allowing a Token Ring link to be made through two dissimilar media.  
Cabletron Systems also provides Token Ring Port Interface Module, or TPIM slots  
on all of its standalone and stackable Token Ring networking devices. These TPIM  
slots can be used as Ring-In/Ring-Out ports for the extension of the Token Ring  
network (discussed below) or used as individual station connections to devices  
requiring custom media links.  
Port Count  
The provision of a sufficient number of ports is perhaps the easiest and most  
straightforward portion of the Token Ring network design process. As all of the  
Cabletron Systems standalone Token Ring networking products are also stackable  
devices, any time a particular location requires more ports than can be supplied  
by one device, an STH stackable Token Ring hub can be placed atop it. This new  
device will provide the same management capabilities as the base device, and a  
greater number of available ports.  
This stacking process can be continued until either the maximum number of  
stations on the ring has been reached, or until a single stack incorporates one  
stackable base device and four stackable hubs. The limitations of the stackable  
system will not allow more than five devices to be associated with one another in  
a single stack.  
Should the port count supplied by a maximum-size stack not be enough to  
accommodate the user count of an installation, the network will have to be  
extended, using Ring-In/Ring-Out ports.  
Ring Extensions  
Ring extension allows for the growth of a Token Ring network beyond the  
limitations of a single stack. The use of Ring-In/Ring-Out (RI/RO) ports allows  
extended lengths of cabling to be used to connect stacks or standalone devices.  
RI/RO ports do not provide segmentation functions or create a  
new Token Ring network.  
NOTE  
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Token Ring  
This extension of the ring can be used to allow the Token Ring network to connect  
widely-separated groups of stations in a single ring, or can be used to support  
greater numbers of users than a single Token Ring stack can accommodate. A  
Token Ring stack of maximum size will provide for the connection of 120 stations,  
well below the 250 station maximum of the IEEE 802.5 standard for some cabling  
types. If a Network Designer faced a situation in which a maximum-size stack  
had not been able to support all the required connections, the addition of an  
RI/RO link between the full stack and a new stack would allow the network to  
support up to another 120 stations.  
These RI/RO connections for ring extension are made using specialized PIMs  
called TPIMs, or Token Ring Port Interface Modules.  
Management functionality provided by an intelligent stack base  
is not distributed to non-intelligent devices that are connected  
NOTE  
to that base through RI/RO ports.  
Design Example  
The following example traces the design of a small office network. The network is  
intended for a newly-formed Health Maintenance Organization (HMO), and  
consists of a series of related departments, each having nearly equal demands of  
the network. The Network Designer has examined the needs of the end users and  
the organization of the stations and facility, and has decided that a single, 16Mbps  
Token Ring network will offer the necessary performance and reliability to this  
network. The cabling to be used will be Category 5 UTP cable, and all the cable  
runs have been determined to be within the limitations of the Token Ring  
networking technology.  
The HMO network will consist of 45 stations: 15 office receptionists, 12 doctors’  
offices, 3 pharmacy stations, 3 records stations, 8 accounting and billing stations,  
and 4 management personnel. None of these stations has any particular  
importance over others from the point of view of the Network Designer, and there  
is currently no desire to provide internetworking capabilities or segmentation to  
the network.  
Examining the first networking device selection criteria, the Network Designer,  
who is familiar with the use of both SNMP and RMON as diagnostic and  
fault-aversion tools, opts to investigate the short-term cost savings that would be  
provided by selecting the STHI series of Token Ring concentrators rather than the  
MicroMMAC-T series of concentrators. The Network Designer eliminates the  
non-intelligent devices and those devices which provide management functions  
more extensive than SNMP. The resulting selection field is summarized below.  
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Token Ring  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
STHI-22/24  
STHI-42/44  
stack base  
stack base  
SNMP  
SNMP  
UTP  
STP  
12/24  
12/24  
2 TPIMs  
2 TPIMs  
When examining the Media characteristics of the devices remaining in the  
selection field, the Network Designer immediately eliminates the STHI-42/44  
from consideration. The network being designed will use UTP cabling, which is  
not directly supported by the STHI-42/44.  
Max  
Management  
Product  
STHI-22/24  
Type  
Media Port Count PIMs/BRIMs  
UTP 12/24 2 TPIMs  
stack base  
SNMP  
Examining the port count available from the STHI-22/24 devices, the Network  
Designer notes that even the STHI-24, which provides 24 station ports, will not  
meet the required station count of 45. As the STHI-24 supports the use of TPIMs  
for the creation of RI/RO connections, it would be possible to purchase a second  
STHI-24 and four TPIMs of a matching media type and connect the two devices  
through the RI/RO ports. This solution, while ideal in situations where users are  
widely dispersed or located in separate facilities, forces the Network Designer to  
purchase another intelligent device, and pay for the management capabilities  
twice. In this example, the use of the STHI-24’s stackable hub capabilities will  
provide a significant cost savings.  
As the STHI-24 is a stack base, up to four STH non-intelligent hubs can be stacked  
on top of it and receive the STHI-24’s SNMP management functionality.  
8-6  
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Token Ring  
Looking back at the initial selection field, the Network Designer locates the  
non-intelligent stackable devices and examines them for compliance with the  
needs of the network. The STH-22/24 non-intelligent stackable hub supports UTP  
cabling, and provides either 12 or 24 ports of station connectivity. The addition of  
an STH-24 to the STHI-24 already in the design would supply 48 ports of Token  
Ring station connectivity and four RI/RO ports for future links if required. The  
STHI-24 could also support the addition of up to three more STH devices,  
accommodating up to 72 additional station connections. The network, as  
Accounting  
Management  
Pharmacy  
Records  
Reception  
Doctors  
2094n27  
Figure 8-1. Token Ring Small Office Implementation  
Token Ring Workgroup Design  
8-7  
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Token Ring  
8-8  
Token Ring Workgroup Design  
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Appendix A  
Charts and Tables  
This appendix provides a central location for a series of tables that contain useful network design  
information.  
Workgroup Design Tables  
Ethernet  
Table A-1. Shared Ethernet Workgroup Devices  
Max  
Management  
Product  
MR9T-E  
Type  
Media  
Port Count PIMs/BRIMs  
repeater  
stackable  
stackable  
stackable  
NONE  
UTP  
UTP  
UTP  
8
1 EPIM  
1 EPIM  
2 EPIMs  
1 EPIM  
a
SEH-22/32  
SEH-24/34  
SEH-22FL  
NONE  
12  
24  
12  
a
NONE  
a
NONE  
Multimode  
Fiber Optics  
SEHI-22/32  
SEHI-24/34  
SEHI-22FL  
stack base  
stack base  
stack base  
SNMP  
SNMP  
SNMP  
UTP  
UTP  
12  
24  
12  
1 EPIM  
2 EPIMs  
1 EPIM  
Multimode  
Fiber Optics  
MicroMMAC-22/32E  
MicroMMAC-24/34E  
stack base  
stack base  
RMON  
RMON  
UTP  
12  
24  
1 EPIM  
1 BRIM  
UTP  
2 EPIMs  
1 BRIM  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
A-1  
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Charts and Tables  
Table A-2. Ethernet Workgroup Switches  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
NBR-220  
NBR-420  
SNMP  
SNMP  
0
0
2
4
2 EPIMs  
4 EPIMs  
4 EPIMs  
2 BRIMs  
NBR-620  
SNMP  
0
6
FN10  
SNMP  
UTP  
UTP  
12/24  
12  
12/24  
13  
0
ESX-1320  
RMON  
1 BRIM  
Multimode  
Fiber Optics  
ESX-1380  
RMON  
12  
13  
1 BRIM  
Fast Ethernet  
Table A-3. Shared Fast Ethernet Workgroup Devices  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
a
SEH100TX-22  
SEHI100TX-22  
stackable  
stack base  
NONE  
UTP  
UTP  
22  
22  
1 EPIM  
SNMP  
2 EPIMs  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
A-2  
Workgroup Design Tables  
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Charts and Tables  
Table A-4. Fast Ethernet Workgroup Switches  
Max  
Management  
Switch  
Interfaces  
Name  
Media  
Port Count  
PIMs/BRIMs  
FN100-8TX  
FN100-16TX  
SNMP  
SNMP  
UTP  
UTP  
8
8
0
0
16  
16  
Multimode  
Fiber Optics  
FN100-8FX  
SNMP  
SNMP  
8
8
0
0
Multimode  
Fiber Optics  
FN100-16FX  
16  
16  
Token Ring  
Table A-5. Token Ring Workgroup Devices  
Max  
Management  
Product  
Type  
Media Port Count PIMs/BRIMs  
a
STH-22/24  
STH-42/44  
STHI-22/24  
STHI-42/44  
stackable  
stackable  
stack base  
stack base  
NONE  
UTP  
STP  
UTP  
STP  
UTP  
STP  
12/24  
12/24  
12/24  
12/24  
12/24  
12/24  
2 TPIM  
2 TPIM  
2 TPIM  
2 TPIM  
2 TPIM  
2 TPIM  
a
NONE  
SNMP  
SNMP  
RMON  
RMON  
MicroMMAC-22T/24T stack base  
MicroMMAC-42T/44T stack base  
a. These products can be managed through the addition of an intelligent stackable device to their stack.  
Workgroup Design Tables  
A-3  
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Charts and Tables  
PIMs and BRIMs  
Table A-6. PIM Reference Table  
Technology Media  
Ethernet  
PIM  
Connector  
EPIM-A  
EPIM-C  
EPIM-F1  
AUI  
DB15 (Male)  
RG58  
Ethernet  
Ethernet  
Thin Coaxial  
Multimode  
Fiber Optics  
SMA  
EPIM-F2  
EPIM-F3  
Ethernet  
Ethernet  
Multimode  
Fiber Optics  
ST  
Single Mode  
Fiber Optics  
ST  
EPIM-T  
EPIM-X  
Ethernet  
Ethernet  
UTP  
AUI  
RJ45  
DB15  
(Female)  
Fast Ethernet Interface  
Module-100TX  
Fast Ethernet  
Fast Ethernet  
Fast Ethernet  
Fast Ethernet  
Token Ring  
UTP  
RJ45  
SC  
SC  
SC  
ST  
Fast Ethernet Interface  
Module-100FX  
Multimode  
Fiber Optics  
Fast Ethernet Interface  
Module-100F3  
Single Mode  
Fiber Optics  
Fast Ethernet Interface  
Module-100FMB  
Multimode  
Fiber Optics  
TPIM-F2  
Multimode  
Fiber Optics  
TPIM-F3  
Token Ring  
Single Mode  
Fiber Optics  
ST  
TPIM-T1  
TPIM-T2  
TPIM-T4  
Token Ring  
Token Ring  
Token Ring  
STP  
UTP  
UTP  
DB-9  
RJ45  
RJ45  
A-4  
Workgroup Design Tables  
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Charts and Tables  
Table A-6. PIM Reference Table (Continued)  
PIM  
Technology  
FDDI  
Media  
Connector  
FPIM-00  
FPIM-01  
Multimode  
Fiber Optics  
FDDI MIC  
SC  
FDDI  
Multimode  
Fiber Optics  
FPIM-02  
FPIM-04  
FPIM-05  
FDDI  
FDDI  
FDDI  
UTP  
STP  
RJ45  
RJ45  
Single Mode  
Fiber Optics  
FDDI MIC  
FPIM-05  
APIM-11  
APIM-21  
APIM-22  
FDDI  
Single Mode  
Fiber Optics  
SC  
SC  
SC  
SC  
ATM (TAXI)  
ATM (OC3c)  
ATM (OC3c)  
Multimode  
Fiber Optics  
Multimode  
Fiber Optics  
Single Mode  
Fiber Optics  
APIM-29  
APIM-67  
ATM (STS3c)  
ATM (DS3)  
WAN (56K)  
UTP  
RJ45  
RG58  
RJ45  
RJ45  
Thin Coaxial  
Custom  
Custom  
WPIM-DDS  
WPIM-DI  
WAN (Drop &  
Insert)  
WPIM-E1  
WPIM-SY  
WAN (E1)  
Custom  
Custom  
RJ45  
WAN  
(Synchronous  
DTE)  
26-pin  
RS530A  
WPIM-T1  
WAN (T1)  
Custom  
RJ45  
Workgroup Design Tables  
A-5  
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Charts and Tables  
Table A-7. BRIM Reference Table  
Connector  
Type  
BRIM  
BRIM-E6  
Technology  
Ethernet  
Fast Ethernet  
FDDI  
EPIM  
EPIM  
BRIM-E100  
BRIM-F6  
FPIM (2)  
APIM  
BRIM-A6  
ATM  
BRIM-A6DP  
BRIM-W6  
ATM  
APIM (2)  
WPIM  
WAN  
Table A-8. BRIM Interoperability Table  
MicroMMAC-  
22/24/32/34E  
NBR-620  
BRIM #1  
NBR-620  
BRIM #2  
a
BRIM  
ESX-1320/1380  
NO  
BRIM-E6  
YES  
YES  
NO  
BRIM-E100  
BRIM-F6  
NO  
YES  
YES  
NO  
YES  
NO  
YES  
NO  
NO  
NO  
NO  
NO  
NO  
NO  
NO  
YES  
YES  
NO  
YES  
NO  
BRIM-A6  
BRIM-A6DP  
BRIM-W6  
a. This table is subject to change as new BRIM modules and revised firmware are released.  
A-6  
Workgroup Design Tables  
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Charts and Tables  
Networking Standards and Limitations  
Ethernet  
Distance Limitations  
Table A-9. Ethernet Standard Distance Limitations  
Media  
Thick Coax  
Max Distance  
500 m  
185 m  
50 m  
Thin Coax  
Standard AUI  
Office AUI  
16.5 m  
100 m  
1000 m  
1000 m  
UTP  
Fiber Optics (Multimode)  
Fiber Optics (Single Mode)  
General Rules  
Table A-10. Ethernet General Rules  
Max # Stations  
1,024  
Max Repeater Hops/Path  
Max # Bridges/Path  
Topologies  
4
7
Bus, Star, Tree, Hybrid  
Networking Standards and Limitations  
A-7  
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Charts and Tables  
Fast Ethernet  
Distance Limitations  
Table A-11. Fast Ethernet (100BASE-TX/FX) Distance Limitations  
Media  
Max Distance  
UTP  
Fiber Optics (Multimode)  
100 m  
412 m  
Network Radii  
Table A-12. Fast Ethernet Maximum Network Radii  
UTP &  
Buffered  
Uplink  
Fiber Optics  
andBuffered  
Uplink  
Repeater  
Class  
UTP & Fiber  
Optics  
UTP  
Fiber Optics  
Class I  
200 m  
200 m  
260 m  
N/A  
272 m  
320 m  
500 m  
N/A  
800 m  
N/A  
Class II  
A-8  
Networking Standards and Limitations  
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Charts and Tables  
Token Ring  
Distance Limitations  
Table A-13. Token Ring Maximums  
Max # of Stations  
Cable  
Max Lobe Length  
Media  
Circuitry  
Type  
4 Mbps  
16 Mbps  
4 Mbps  
16 Mbps  
STP  
active  
IBM Types 1, 2  
IBM Types 6, 9  
IBM Types 1, 2  
IBM Type 9  
250  
250  
250  
250  
150  
150  
100  
100  
250  
250  
250  
136  
250  
136  
150  
150  
100  
100  
250  
250  
300 m  
200 m  
200 m  
133 m  
250 m  
200 m  
130 m  
100 m  
2000 m  
2000 m  
150 m  
100 m  
100 m  
66 m  
a
passive  
active  
UTP  
Category 5  
120 m  
100 m  
85 m  
Categories 3, 4  
Category 5  
passive  
active  
Categories 3, 4  
Multimode  
60 m  
Fiber Optics  
2000 m  
2000 m  
Single Mode  
a. IBM Type 6 cable is recommended for use as jumper cabling only, and should not be used for facility cabling  
installations.  
Networking Standards and Limitations  
A-9  
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Charts and Tables  
Ring-In/Ring-Out Limitations  
Table A-14. Ring-In/Ring-Out Distances  
Max Distance  
(4 Mbps)  
Max Distance  
(16 Mbps)  
Media  
Shielded Twisted Pair  
Unshielded Twisted Pair  
Category 3/4  
770 m  
346 m  
200 m  
250 m  
100 m  
120 m  
Category 5  
Fiber Optics (Multimode)  
Fiber Optics (Single Mode)  
2000 m  
2000 m  
2000 m  
2000 m  
General Rules  
Table A-15. Token Ring General Rules  
Max # Stations/Ring  
260  
7
Max # Bridges  
Topologies  
Logical Ring/Physical Star  
A-10  
Networking Standards and Limitations  
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Charts and Tables  
FDDI  
FDDI Distance Limitations  
Table A-16. FDDI Distance Limitations  
Media  
PMD Standard  
Max Link Distance  
Fiber Optics (Multimode)  
Fiber Optics (Single Mode)  
MMF-PMD  
SMF-PMD  
TP-PMD  
2 km  
60 km  
100 m  
100 m  
a
Unshielded Twisted Pair  
b
Shielded Twisted Pair  
a. Category 5 UTP cabling only  
b. IBM Type 1 STP cabling only  
General Rules  
Table A-17. FDDI General Rules  
Max # Stations/Ring  
500  
Max Total Ring Length  
Topologies  
100 km  
Logical Ring, Tree  
Networking Standards and Limitations  
A-11  
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Charts and Tables  
A-12  
Networking Standards and Limitations  
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Glossary  
This glossary provides brief descriptions of some of the recurrent terms in the main text, as well as  
related terms used in discussions of the relevant networking discussions. These descriptions are not  
intended to be comprehensive discussions of the subject matter. For further clarification of these terms,  
you may wish to refer to the treatments of these terms in the main text.  
Words in the glossary description text listed in boldface type indicate other entries in the glossary  
which may be referred to for further clarification.  
100BASE-FX  
100BASE-TX  
10BASE2  
IEEE standard which details the operating and performance  
characteristics of fiber optic cabling in Fast Ethernet networks.  
IEEE standard which deals with the use and performance of UTP cabling  
in Fast Ethernet networks.  
IEEE standard which governs the operation of devices connecting to  
Ethernet thin coaxial cable.  
10BASE5  
IEEE standard which governs the operation of devices connecting to  
Ethernet thick coaxial cable.  
10BASE-FL  
10BASE-T  
A/B Ports  
IEEE standard which governs the operation of devices connecting to  
Ethernet fiber optic cable. Supersedes previous FOIRL standard.  
IEEE standard which governs the operation of devices connecting to  
Ethernet Unshielded Twisted Pair (UTP) cable.  
FDDI ports which provide connection, in pairs, to the dual  
counter-rotating ring.  
Application  
Architecture  
1: A software operation performed by a workstation or other network  
node. 2: A layer of the OSI Model.  
A collective rule set for the operation of a network. Architectures describe  
the means by which network devices relate to one another. Architecture  
types include Mainframe-Terminals, Peer-to-Peer, and Client-Server.  
ATM  
Asynchronous Transfer Mode. A networking technology that is based on  
the use of connections between communicating devices that are set up,  
used, and then eliminated.  
Glossary-1  
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Attenuation to Client-Server  
Attenuation  
Loss of signal power (measured in decibels) due to transmission through  
a cable. Attenuation is dependent on the type, manufacture and  
installation quality of cabling, and is expressed in units of loss per length,  
most often dB/m.  
AUI  
Attachment Unit Interface. A cabling type used in Ethernet networks,  
designed to connect network stations and devices to transceivers.  
Backbone  
Bit  
A portion of a network which provides the interconnection of a number  
of separate, smaller networks.  
Binary Digit. A bit is the smallest unit of information, consisting of a  
single binary number. A bit is represented by a numerical value of 1 or 0.  
BOOTP  
Bootstrap Protocol. Checks MIB variables of an SNMP manageable  
device to determine whether it should start up using its existing firmware  
or boot up from a network server specifically configured for the purpose.  
Bridge  
Bridges are network devices which connect two or more separate  
network segments while allowing traffic to be passed between the  
separate networks when necessary. Bridges read in packets and decide to  
either retransmit them or block them based on the destination to which  
the packets are addressed.  
BRIM  
Bridge/Router Interface Module. BRIMs are added to BRIM-capable  
Cabletron Systems equipment to provide connections to external  
networks through an integrated bridge or router.  
Broadcast  
Buffered Uplink  
A type of network transmission; a broadcast transmission is one which is  
sent to every station on the network, regardless of location, identification,  
or address.  
A type of Fast Ethernet connection that provides retiming and  
regeneration of signals. In effect, the buffered uplink provides the  
distance characteristics of a bridged connection without performing  
actual segmentation.  
Client  
A workstation or node which obtains services from a server device  
located on the network.  
Client-Server  
A computing model which is based on the use of dedicated devices  
(servers) for the performance of specific computational or networking  
tasks. These servers are accessed by several clients, workstations which  
cannot perform those functions to the same extent or with the same  
efficiency as the servers.  
Glossary-2  
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Coaxial to Decryption  
Coaxial  
An Ethernet media type which consists of a core of electrically conductive  
material surrounded by several layers of insulation and shielding.  
Concentrator  
Congestion  
A network device which allows multiple network ports in one location to  
share one physical interface to the network.  
An estimation or measure of the utilization of a network, typically  
expressed as a percentage of theoretical maximum utilization of the  
network.  
Connectivity  
Crossover  
The physical connection of cabling or other media to network devices.  
The coupling of media to the network.  
A length of multi-stranded cable in which the transmit wire(s) of one end  
is/are crossed over within the cable to connect to the receive wire(s) of  
the other end. Crossovers are used to connect devices to like devices,  
ensuring that transmit and receive connections are properly made.  
Crosstalk  
CSMA/CD  
A corruption of the electrical signal transmitted through a Shielded or  
Unshielded Twisted Pair cable. Crosstalk refers to signals on one strand  
or set of strands affecting signals on another strand or set of strands.  
Carrier Sense Multiple Access with Collision Detection. CSMA/CD is the  
basis for the operation of Ethernet networks. CSMA/CD is the method  
by which stations monitor the network, determine when to transmit data,  
and what to do if they sense a collision or other error during that  
transmission.  
Data  
Information, typically in the form of a series of bits, which is intended to  
be stored, altered, displayed, transmitted, or processed.  
Data Loop  
A condition caused by the creation of duplicate paths which network  
transmissions could follow. Data loops are created by the use of  
redundant connections between network segments or devices. Ethernet  
networks cannot effectively function with data loops present. To allow  
the creation of fault-tolerant networks, data loops are automatically  
detected and eliminated by the Spanning Tree algorithm.  
DB15  
A 15-pin connector used to terminate transceiver cables in accordance  
with the AUI specification.  
DB9  
A 9-pin connector, typically used in Token Ring networks and for serial  
communications between computers.  
Decryption  
The translation of data from an encrypted (see encryption) form into a  
form both recognizable and utilizable by a workstation, node, or network  
device.  
Glossary-3  
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Dedicated to Fault-Tolerance  
Dedicated  
Assigned to one purpose or function.  
Device (network)  
Any discrete electronic item connected to a network which either  
transmits and receives information through it, facilitates that  
transmission and reception, or monitors the operation of the network  
directly.  
DLM  
Distributed LAN Monitor. DLM is a feature of some SNMP management  
devices which allows that device to locally monitor other devices under  
its control and report to a central network management station any noted  
errors. This frees the network management station from directly  
monitoring every SNMP device.  
DNI  
Desktop Network Interface. DNI cards are devices which are added to  
workstations to provide them with a connection to a network (NIC).  
Dual Attached  
Dual Homing  
Connected to an FDDI dual counter-rotating ring through the use of A/B  
ports.  
A station connection method for FDDI which connects a device’s A/B  
ports to the M ports of two separate dual-attached concentrator devices,  
providing fault-tolerance.  
EEPROM  
Electronic Erasable Programmable Read-Only Memory.  
Encryption  
A security process which encodes raw data into a form that cannot be  
utilized or read without decryption.  
EPIM  
Ethernet Port Interface Module. EPIMs are added to  
specifically-designed slots in Cabletron Systems Ethernet products to  
provide connections to external media. EPIMs allow a great flexibility in  
the media used to connect to networks.  
Ethernet  
A networking technology which allows any station on the network to  
transmit at any time, provided it has checked the network for existing  
traffic, waited for the network to be free, and checked to ensure the  
transmission did not suffer a collision with another transmission. See also  
CSMA/CD.  
Fast Ethernet  
A networking technology based on the Ethernet technology. Fast  
Ethernet operates at 10 Mbps, ten times the speed of standard Ethernet  
networks.  
Fault-Tolerance  
The ability of a design (device or network) to operate at full or reduced  
capacity after suffering a failure of some essential component or  
connection. See also redundant.  
Glossary-4  
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FDDI to Impedance  
FDDI  
Fiber Distributed Data Interface. A high-speed networking technology.  
FDDI requires that stations only transmit data when they have been  
given permission by the operation of the network, and dictates that  
stations will receive information at pre-determined intervals. See also  
Token.  
Fiber Optics  
Network media made of thin filaments of glass surrounded by a plastic  
cladding. Fiber optics transmit and receive information in the form of  
pulses of light. See multimode and single mode.  
File  
A collection of related data.  
Fileserver  
A network server device which stores and maintains data files for access  
and modification by users.  
Firmware  
Flash EEPROM  
FNB  
The software instructions which allow a network device to function.  
See EEPROM.  
Flexible Network Bus. A Cabletron Systems backplane design which  
enables an FNB-configured chassis to support multiple network  
technologies simultaneously.  
Frame  
A group of bits that form a discrete block of information. Frames contain  
network control information or data. The size and composition of a frame  
is determined by the network protocol being used. Frames are typically  
generated by operations at the Data Link Layer (Layer 2) of the  
OSI Model.  
Gateway  
A device which connects networks with dissimilar network architectures  
and which operates at the Application Layer of the OSI Model. May also  
be used to refer to a router.  
Heartbeat  
See SQE.  
Hexadecimal  
A base 16 numerical system. Digits in hexadecimal run from 0 to 9 and  
continue from A to F, where F is equivalent to the decimal number 16.  
Host  
A device which acts as the source or destination of data on the network.  
Institute of Electrical and Electronic Engineers. A standards-making body.  
Internet Engineering Task Force. A standards-making body.  
IEEE  
IETF  
Impedance  
A measure of the opposition of electrical current or signal flow in a length  
of cable.  
Glossary-5  
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Interface to MAC Address  
Interface  
A connection to a network. Unlike a port, an interface is not necessarily  
an available physical connector accessible through the front panel of a  
device. Interfaces may be used as backplane connections, or may be  
found only in the internal operation of a module (All ports are interfaces,  
but not all interfaces are ports).  
Internet  
A world-wide network which provides access through a vast chain of  
private and public LANs.  
Interoperability  
The capacity to function in conjunction with other devices. Used  
primarily to indicate the ability of different vendors’ networking  
products to work together cohesively.  
IP  
Internet Protocol.  
IP Address  
Internet Protocol address. The IP address is associated, by the network  
manager or network designer, to a specific interface. The availability of IP  
addresses is controlled by the IANA.  
ISO  
International Organization for Standardization. The ISO has developed a  
standard model on which network operation is based, called the OSI  
Model.  
Jitter  
Degradation of network signals due to a loss of synchronization of the  
electrical signals. Jitter is often a result of passing a signal through too  
many repeaters.  
LAN  
Local Area Network.  
LANVIEW  
A system which relates diagnostic, troubleshooting, and operational  
information pertaining to network devices through the use of  
prominently displayed LEDs.  
LDRAM  
LED  
Local Dynamic Random Access Memory.  
Light Emitting Diode. A simple electronic light, used in networking  
equipment to provide diagnostic indicators. Also used as a light source  
for some fiber optic communications equipment.  
Load  
An indication of network utilization.  
M Ports  
FDDI connectivity ports located on concentrator devices, to which end  
nodes connect through their S ports.  
MAC Address  
Media Access Control address. The MAC address is associated, usually at  
manufacture, with a specific interface.  
Glossary-6  
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MAU to Network Radius  
MAU  
Multistation Access Unit.  
Mbps  
Megabits Per Second. Mbps indicates the number of groups of 1000 bits  
of data that are being transmitted through an operating network. Mbps  
can be roughly assessed as a measure of the operational “speed” of the  
network.  
Media  
Physical cabling or other method of interconnection through which  
network signals are transmitted and received.  
MIC Connector  
1: Token Ring genderless connector. 2: FDDI fiber optic connector which  
may be keyed to act as an M or S connector or A/B connector.  
Micron (µ)  
A micrometer, one millionth of a meter.  
MIM  
Media Interface Module. See also Module.  
Vital to the operation of a network, company, or agency.  
Mission-Critical  
Modular Chassis  
A device which provides power, cooling, interconnection, and  
monitoring functions to a series of flexible and centralized modules for  
the purposes of creating a network or networks.  
Module  
A discrete device which is placed in a modular chassis to provide  
functionality which may include, but is not limited to, bridging, routing,  
connectivity, and repeating. Modules are easily installed and removed.  
Also, any device designed to be placed in another device in order to  
operate.  
Multichannel  
Multimode  
A Cabletron Systems Ethernet design which provides three separate  
network channels (of Ethernet or Token Ring technology) through the  
backplane of a chassis, allowing for the creation of multiple networks in a  
single chassis.  
A type of fiber optics in which light travels in multiple modes, or  
wavelengths. Signals in Multimode fiber optics are typically driven by  
LEDs.  
Nanometer  
NAUN  
One billionth of a meter.  
Nearest Active Upstream Neighbor.  
Network Radius  
The distance between the two stations on a network that are most remote  
from one another and the cabling and repeater devices between them.  
Network radius calculations are essential to ensuring the proper  
operation of a Fast Ethernet network.  
Glossary-7  
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Node to Protocol  
Node  
Any single end station on a network capable of receiving, processing, and  
transmitting packets.  
NVRAM  
Non-Volatile Random Access Memory. Memory which is protected from  
elimination during shutdown and between periods of activity, frequently  
through the use of batteries.  
Octet  
A numerical value made up of eight binary places (bits). Octets can  
represent decimal numbers from zero (0000 0000) to 255 (1111 1111).  
OSI Model  
Open Standards Interconnect. A model of the way in which network  
communications should proceed from the user process to the physical  
media and back.  
Out-Of-Band  
Packet  
Performed without requiring the operation of the network technology.  
Most commonly used in reference to local management operations.  
A discrete collection of bits that form a block of information. Packets are  
similar to frames. Packets are typically generated at the Network Layer  
(Layer 3) of the OSI Model, and are encapsulated in frames before being  
transmitted onto a network media.  
Passive  
Not utilizing per-port reclocking and regeneration of the signal which is  
propagated throughout the device. Commonly applied to Token Ring  
equipment to distinguish it from active devices.  
Phantom Current  
Plenum  
A weak voltage passed by Token Ring end nodes to the MAU to open the  
relay for that port.  
A cabling term which indicates a cable with insulating material that is  
considered safe to use in return-air plenum spaces (in contrast to PVC  
insulation) due to its low relative toxicity if ignited.  
Port  
A physical connector which is used as an interface to cabling with  
modular or pinned connectors. Ports are associated with Interfaces.  
Port Assignment  
The association, through software management, of specific ports on a  
network device to specific channels of a backplane. This assignment is  
done on an individual port basis.  
Protocol  
A set of rules governing the flow of information within a communications  
infrastructure. Protocols control operations such as frame format, timing,  
and error correction. See also Architecture.  
Glossary-8  
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PVC to Server  
PVC  
Polyvinyl Chloride. A material commonly used in the fabrication of cable  
insulation. This term is used to describe a non-plenum rated insulating  
material. See also Plenum. PVC releases toxic smoke when burned.  
Redundant  
Extra or contingent. A redundant system is one that is held in reserve  
until an occurrence such as a failure of the primary system causes it to be  
required.  
Relay  
An electrical switch which opens and closes in response to the application  
of voltage or current.  
Repeater  
A network device consisting of a receiver and transmitter which is used  
to regenerate a network signal to increase the distance it may traverse.  
Ring-In/Ring-Out  
Token Ring connections which are made between MAUs utilizing two  
separate physical cables and incorporating an auto-wrap recovery  
feature.  
RJ45  
A modular connector style used with twisted pair cabling. The RJ45  
connector resembles the modern home telephone connector (RJ11).  
RMIM  
Repeating Media Interface Module. A term used to indicate a family of  
Cabletron Systems Ethernet Media Interface Modules (See MIM) which  
are capable of performing their own repeater functions.  
Router  
A router is a device which connects two or more different network  
segments, but allows information to flow between them when necessary.  
The router, unlike a bridge, examines the data contained in every packet  
it receives for more detailed information. Based on this information, the  
router decides whether to block the packet from the rest of the network or  
transmit it, and will attempt to send the packet by the most efficient path  
through the network.  
S Ports  
FDDI ports which are used by FDDI stations and end nodes to make  
single attached connections to FDDI concentrators.  
SDRAM  
Shared Dynamic Random Access Memory.  
Segment  
A portion of a network which is separated from other networks. A  
segment may be one portion of a bridged, switched, or routed network.  
Segments must be capable of operating as their own networks, without  
requiring the services of other portions of the network.  
Server  
A workstation or host device that performs services for other devices  
(clients) on the network.  
Glossary-9  
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SIMM to Switch  
SIMM  
Single In-line Memory Module. A collection of Random Access Memory  
(RAM) microprocessors which are placed on a single, replaceable printed  
circuit board. These SIMMs may be added to some devices to expand the  
capacity of certain types of memory.  
Single Attached  
Single Mode  
Connected to an FDDI network through a single cable which does not  
provide for auto-wrap functions.  
A type of fiber optics in which light travels in one predefined mode, or  
wavelength. Signals in single mode fiber optics are typically driven by  
lasers. The use of lasers and the transmission characteristics of single  
mode fiber optics allow the media to cover greater distances than  
multimode fiber optics.  
SMA  
Sub-Miniature Assembly. A modular connector and port system used in  
multimode fiber optic cabling. The SMA connector is threaded, and is  
screwed into an SMA port.  
Spanning Tree  
A mathematical comparison and decision algorithm performed by  
Ethernet bridges at power-up. Spanning tree detects the presence of data  
loops and allows the bridges to selectively activate some ports while  
others remain in a standby condition, avoiding the data loops and  
providing redundant paths in the event of bridge failures.  
SQE  
ST  
Signal Quality Error. A self-monitoring test performed by some Ethernet  
equipment which examines the status of the device at arbitrary and  
predefined intervals.  
Straight-Tip. A modular connector and port system used with both  
multimode and single mode fiber optic cabling. The ST connector utilizes  
an insert and twist-lock mechanism.  
Station  
STP  
See node.  
Shielded Twisted Pair. Refers to a type of cabling, most commonly used in  
Token Ring networks, which consists of several strands of cables  
surrounded by foil shielding, which are twisted together. See also UTP.  
Straight-Through  
Switch  
A length of multi-stranded cable in which the transmit wire(s) of one end  
is/are passed directly through the cable to the same location on the other  
end. Straight-through cables are used for most facility cabling. See also  
crossover.  
A network device which connects two or more separate network  
segments and allows traffic to be passed between them when necessary. A  
switch determines if a packet should be blocked or transmitted based on  
the destination address contained in that packet.  
Glossary-10  
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TCP to UTP  
TCP  
Transmission Control Protocol.  
Terminal  
A device for displaying information and relaying communications.  
Terminals do not perform any processing of data, but instead access  
processing-capable systems and allow users to control that system.  
Throughput  
Token  
The rate at which discrete quantities of information (typically measured  
in Mbps) are received by or transmitted through a specific device.  
A particular type of frame which informs a station in the Token Ring and  
FDDI network technologies that it may transmit data for a specified  
length of time. Once that time has expired, the station must stop  
transmitting and pass the token along to the next station in the network.  
Token Ring  
A network technology which requires that stations only transmit data  
when they have been given permission by the reception of a Token, and  
dictates that stations will receive information at pre-determined intervals  
and in a definite series.  
Topology  
TP-PMD  
The physical organization of stations and devices into a network.  
Twisted Pair - Physical Medium Dependent.  
Transceiver  
A device which transmits and receives. A transceiver provides the  
electrical or optical interface to the network media, and may convert  
signals from one media for use by another.  
User  
UTP  
Any person who utilizes a workstation or node on the network.  
Unshielded Twisted Pair. A type of network media which consists of a  
number of individual insulated cable strands which are twisted together  
in pairs.  
Glossary-11  
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UTP to UTP  
Glossary-12  
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Index  
Numerics  
E
100BASE-FX 2-3  
100BASE-TX 2-3  
EPIM 4-3  
Ethernet 2-2, 6-1  
cable lengths 2-2  
high-end department 6-19  
home office 6-5  
A
Active circuitry 2-6  
APIM 4-5  
remote office 6-16  
shared devices 6-2  
signal path 2-3  
Assistance 1-3  
small office 6-11  
station count 2-3  
switched devices 6-4  
Expansion (of networks) 5-15  
B
Backbones  
collapsed 5-19  
definition 5-17  
device 5-20  
F
distributed 5-18  
Fast Ethernet 7-9  
selection 5-21  
Bandwidth 2-2  
Bridge 3-2  
Fast Ethernet 2-3, 7-1  
100BASE-FX 2-3  
100BASE-TX 2-3  
buffered uplink 2-4  
cable length 2-4  
high-end department 7-6  
network radius 2-4  
repeater classes 2-3  
shared devices 7-1  
small office 7-3  
BRIM 3-7, 4-8, 4-8 to 4-10  
C
Chapter summaries 1-2  
Collapsed backbone 5-19  
Concentrator 3-2  
CSMA/CD 2-2  
station count 2-5  
switched devices 7-2  
Customer Support 1-3  
Fast Ethernet Interface Modules 4-3  
FPIM 4-4  
Frontier 3-6  
D
Device backbone 5-20  
Distributed backbone 5-18  
Document conventions 1-3  
Document organization 1-2  
G
Geographical proximity 5-3  
Index-1  
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Index  
H
S
Help 1-3  
Segmentation 5-2  
Small office 6-11, 7-3, 8-3  
Stackable 3-4  
High-end department 6-19, 7-6  
Home office 6-5  
HubSTACK Interconnect Cables 3-5  
interconnect cable 3-5  
internetworking 3-7  
management 3-6  
Standalone 3-1  
management 3-3  
I
Installation  
planning 5-11  
Interconnect cables 3-5  
internetworking 4-8  
Introduction 1-1  
T
Technical Support 1-3  
Technology  
selection 5-9  
N
Token Ring 2-5, 8-1  
active circuitry 2-6  
link lengths 2-7  
Ring-In/Ring-Out 2-6  
shared devices 8-1  
small office 8-3  
station count 2-8  
TPIM 4-4  
Network  
growth 5-15  
layout 5-10  
planning 5-10  
Network map 5-14  
Network radius 2-4  
Networking Services 1-3  
P
U
PIM 4-1  
Using this Guide 1-1  
ATM 4-5  
decoding 4-2  
Ethernet 4-3  
Fast Ethernet 4-3  
FDDI 4-4  
naming 4-2  
table of types 4-6  
Token Ring 4-4  
Wide Area 4-5  
W
Workgroup 5-2  
designing 5-3  
organization  
common function 5-6  
departmental organization 5-4  
geographical proximity 5-3  
planning 5-2  
technologies 5-9  
Workgroups  
R
Redundancy 5-13  
Related documents 1-4  
Remote office 6-16  
Repeater 3-2  
high-end 6-19  
high-end department 7-6  
home office 6-5  
remote office 6-16  
small office 6-11, 7-3, 8-3  
Ring-In/Ring-Out 2-6  
WPIM 4-5  
Index-2  
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