Cabletron Systems TRMIM-20R Installation Manual

TRMIM-20R

UTP TOKEN RING

CONCENTRATOR

MEDIA INTERFACE MODULE

INSTALLATION GUIDE

CABLETRON SYSTEMS, P. O. Box 5005, Rochester, NH 03867-5005

The Complete Networking Solution

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 March 1991 by:
Cabletron Systems, Inc.

P.O. Box 5005, Rochester, NH 03867-5005
All Rights Reserved

Printed in the United States of America
Order Number: 9030275-01 March 1991

TRMIM-20R, TRMIM-10R, TRRMIM-16, TRMIM-12,
Remote LANVIEW/Windows, SPECTRUM, and MMAC are

trademarks of Cabletron Systems, Inc.

LANVIEW is a registered trademark of Cabletron Systems, Inc.
IBM is a registered trademark of International Business Machines

Corporation.

i

FCC NOTICE

FCC NOTICE

This device complies with Part 15 of FCC rules. Operation is subject
to the following two conditions: (1) this device may not cause harmful
interference, and (2) this device must accept any interference
received, including interference that may cause undesired operation.

WARNING: This equipment uses and generates and can radiate
radio frequency energy and if not installed properly and used in
accordance with the instruction manual, may cause interference to
radio communications. It has been tested and found to comply with
the limits for a Class A digital device pursuant to Part 15 of FCC
Rules, which are designed to provide reasonable protection against
such interference in a commercial environment. Operation of this
equipment in a residential area is likely to cause interference in
which case the user at his own expense will be required to take
whatever steps may be necessary to correct the interference.

If this equipment does cause interference to radio or television, which
can be determined by turning the equipment off and on, the user is
encouraged to try to correct the interference by one or more of the
following measures:

• Re-orient the receiving antenna.

• Relocate the MMAC with respect to the receiving antenna.

• Move the MMAC away from the receiver.

• Plug the MMAC into a different outlet so that the MMAC and
the receiver are on different branch circuits.

If necessary, the user should consult the dealer or an experienced
radio/ television technician for additional suggestions. The user may
find the following booklet prepared by the Federal Communication
Commission helpful:

“How to Identify and Resolve Radio TV Interference Problems”

This booklet is available from the U.S. Government Printing Office,
Washington D.C. 20402 - Stock No. 004-000-00345-4.

ii

CONTENTS

CONTENTS

CHAPTER 1 INTRODUCTION

1.1 Using This Manual ......................................................................1-1

1.2 The TRMIM-20R..........................................................................1-2

1.3 Related Manuals..........................................................................1-4

1.4 Recommended Reading ...............................................................1-5

1.5 Getting Help ................................................................................1-5

CHAPTER 2 INSTALLATION REQUIREMENTS/

SPECIFICATIONS

2.1 Network Requirements ...............................................................2-1

2.1.1 Cable Types .......................................................................2-1

2.1.2 Cable Lengths ...................................................................2-2

2.1.3 Impedance .........................................................................2-4

2.1.4 Attenuation .......................................................................2-4

2.1.5 Maximum Number Of Stations........................................2-4

2.1.6 Crosstalk............................................................................2-4

2.1.7 Noise ..................................................................................2-5

2.1.8 Temperature......................................................................2-5

2.2 Operating Specifications .............................................................2-5

2.2.1 Ring Speed.........................................................................2-5

2.2.2 Ring Sequence...................................................................2-5

2.2.3 Connector Types................................................................2-6

2.2.4 LANVIEW LEDs...............................................................2-8

2.2.5 General Specifications ......................................................2-9

CHAPTER 3 INSTALLING THE TRMIM-20R

3.1 Unpacking The TRMIM-20R ......................................................3-1

3.2 Installing The TRMIM-20R Into The MMAC ............................3-2

3.3 Cabling The TRMIM-20R............................................................3-4

3.3.1 Lobe Cabling......................................................................3-4

3.3.2 Trunk Cabling...................................................................3-6

3.4 Finishing The Installation ..........................................................3-8

iii

CONTENTS

CONTENTS (CONT.)

CHAPTER 4 TESTING AND TROUBLESHOOTING

4.1 Installation Checkout ..................................................................4-1

4.2 Using LANVIEW .........................................................................4-2

APPENDIX A BASIC TOKEN RING NETWORKS

A.1 Basic Token Ring Operation.......................................................A-1

A.2 Design Considerations................................................................A-7

APPENDIX B APPLICATIONS

B.1 Adding To An Existing Token Ring Network............................B-1

B.2 Separate Token Ring Networks In One MMAC........................B-2

B.3 Token Ring Networks Bridged Together ...................................B-3

B.4 MMAC With Ethernet And Token Ring Simultaneously .........B-4

APPENDIX C CALCULATING RING LENGTH

C.1 Rules For Calculating Cable Lengths........................................C-1

C.2 Single Wiring Closet Networks..................................................C-2

C.3 Multiple Wiring Closet Networks ..............................................C-8

C.4 Calculating Mixed Cable Types ...............................................C-15

iv

INTRODUCTION

CHAPTER 1

INTRODUCTION

Welcome to the TRMIM-20R Token Ring Passive Concentrator
Media Interface Module Installation Guide. This guide is

designed to serve as a reference for the installation and
troubleshooting of Cabletron Systems’ TRMIM-20R.

The TRMIM-20R is a token ring network concentrator used in
conjunction with Cabletron System’s Multi Media Access Center
(MMAC). The TRMIM-20R provides ten trunk coupling unit ports
and passive Ring-In and Ring-Out ports. The TRMIM-20R is IEEE

802.5 compliant, and compatible with IBM products. Since the Ring­In/Ring-Out ports are passive and do not regenerate signal timing,
Adjusted Ring Length (ARL) must be considered when planning cable
lengths.

Prior to installing and operating the TRMIM-20R, read through this
manual to familiarize yourself with its content and to gain an
understanding of the features of TRMIM-20R. A general working
knowledge of Token Ring (IEEE 802.5) networks will be helpful when
installing the TRMIM-20R.

1.1 USING THIS MANUAL

Chapter 1, Introduction, covers using this document, briefly
describes features of the TRMIM-20R and token ring, and lists
related manuals.

Chapter 2, Installation Requirements/Specifications, lists
network requirements that must be met before you install the
TRMIM-20R and specifications for the TRMIM-20R.

Chapter 3, Installing the TRMIM-20R, describes installing the
TRMIM-20R into the MMAC, connecting stations, and inserting the
TRMIM-20R into a token ring network.

Page 1-1

INTRODUCTION

Chapter 4, Testing and Troubleshooting, describes LANVIEW,
Cabletron Systems’ built-in visual diagnostic and status monitoring
system, and gives procedures for verifying the proper installation of
the TRMIM-20R.

Appendix A, Basic Token Ring Networks, covers basic operation
and concepts related to the design of token ring networks.

Appendix B, Applications, presents a variety of network
configurations, showing practical applications for several Cabletron
Systems’ token ring products.

Appendix C, Calculating Ring Length, describes methods for
calculating various ring cable lengths in a passive token ring
network.

1.2 THE TRMIM-20R

The TRMIM-20R, shown in Figure 1-1, is a Media Interface Module
(MIM) that can be installed into a Cabletron Systems’ MMAC-8FNB,
MMAC-8, MMAC-5FNB, MMAC-3FNB or MMAC-3.

The TRMIM-20R functions as a ten port concentrator in a token ring
network providing passive Ring-In and Ring-Out ports and ten trunk
coupling ports.

The TRMIM-20R provides two DB-9 and ten RJ-45 connectors on the
front panel. Two DB-9 connectors permit attachment for shielded
twisted pair (STP) Ring-In and one Ring-Out trunk cabling. Ten
unshielded twisted pair (UTP), RJ-45 connectors support trunk
coupling ports for up to ten token ring stations.

The Ring-In and Ring-Out ports support IBM Type 1, 2, 6 and 9 STP
cable. Each of the TRMIM-20R trunk coupling unit ports supports
station connections via voice grade UTP.

Since the Ring-In and Ring-Out ports are passive trunk connections,
trunk cable length must be calculated giving consideration to
Adjusted Ring Length (ARL). Refer to Appendix C, Calculating
Ring Length, to determine trunk cable length.

Page 1-2

INTRODUCTION

The TRMIM-20R supports voice grade UTP at lobe lengths of up to
100 meters at 4 Mbit/sec and up to 60 meters at 16 Mbit/sec.
Supported cable types and lengths are listed in Chapter 2,
Installation Requirements/Specifications.

TRMIM-20R

7

X

8

X

9

X

10
X

RI

RO

1

X

2

X

3

X

4

X

5

X

6

X

UTP

TOKEN RING

Figure 1-1. TRMIM-20R Token Ring Concentrator

Page 1-3

INTRODUCTION

It is possible to have several network types and media in one MMAC,
such as a shielded twisted pair token ring network and a thin-net
Ethernet network. There are a number of configuration guidelines
concerning multiple networks within an MMAC. These guidelines
are listed in Chapter 3, Installing the TRMIM-20R.

Several MMACs can be connected into the same ring network by
installing token ring concentrators (TRMIM-10R/TRMIM-20R) or
token ring repeaters (TRRMIM-16/TRRMIM-26). The choice between
using concentrators or repeaters depends on specific network
configurations.

The TRMIM-20R incorporates LANVIEW, a useful tool to help you
quickly diagnose physical layer network problems. Several LEDs
(light emitting diodes) are located at the front of the TRMIM-20R.
These LEDs indicate the ring speed, detection of a TRMIM-20R
hardware error, and when a specific port is attached to the ring.

A variety of network management tools can be used to control and
monitor the TRMIM-20R, including Cabletron Systems Local
Management, Cabletron Systems Remote LANVIEW Windows, and
Cabletron Systems SPECTRUM.

1.3 RELATED MANUALS

The manuals listed below should be used to supplement the
procedures and other technical data provided in this manual. The
procedures in them will be referenced, where appropriate, but will not
be repeated in this document.

Cabletron Systems’ Multi-Media Access Center Overview and

Set Up Guide.
Cabletron Systems’ TRMIM-10R Token Ring Concentrator

Media Interface Module Installation Guide.
Cabletron Systems’ TRMIM-12 Token Ring Media Interface

Module Installation Guide.
Cabletron Systems’ TRRMIM-16 Token Ring Repeater Media

Interface Module Installation Guide.

Page 1-4

INTRODUCTION

Cabletron Systems’ TRMIM-22 UTP Passive Token Ring Media
Interface Module Installation Guide.

1.4 RECOMMENDED READING

The following publications are recommended if more information is
required on implementing a token ring network.

Local Area Networks, Token Ring Access Method, IEEE
Standard 802.5

Commercial Building Wiring Standard, EIA Standard
Proposal No. 1907-A (if approved, to be published as EIA/TIA-568)

LAN Troubleshooting Handbook, Mark Miller (1989, M&T

Publishing, Inc.)

1.5 GETTING HELP

If you need additional support related to the Cabletron Systems’
TRMIM-20R, or if you have any questions, comments or suggestions
related to this manual, please contact Cabletron Systems Technical
Support at:

Cabletron Systems
P. O. Box 5005
Rochester, NH 03867-0505

Phone: [phone]

Page 1-5

REQUIREMENTS/SPECIFICATIONS

CHAPTER 2

INSTALLATION REQUIREMENTS/

SPECIFICATIONS

Before you attempt to install your TRMIM-20R, review the
installation requirements and operating specifications outlined in
this chapter. The conditions, guidelines and requirements described
in this chapter must be met to obtain satisfactory performance from
this equipment.

2.1 NETWORK REQUIREMENTS

Take care in planning and preparing the cabling and connections for
your network. The quality of the connections, the length of cables
and other conditions of the installation are critical factors in
determining the reliability of your network.

NOTE: While the TRMIM-20R supports voice grade UTP cabling,
some applications, where existing telephone voice grade UTP is used,
may be subject to crosstalk, electrical noise, signal attenuation or other
environmental factors that exceed acceptable limits. This could reduce
the maximum cable lengths or, in extreme cases, prevent using the
existing cables. In some cases acceptable performance will be obtained
by reducing the lobe length or rerouting the cable. Where more severe
interference is encountered, the installation of new cabling may be
necessary.

The following sections describe the network requirements for
TRMIM-20R operation, however, the same requirements apply
whenever UTP cabling is used within a passive ring segment.

2.1.1 Cable Types
Trunk Cabling - The TRMIM-20R supports IBM Type 1, 2, 6 and 9

shielded twisted pair cable.

Page 2-1

REQUIREMENTS/SPECIFICATIONS
Lobe Cabling - In addition to IBM Type 3 unshielded twisted pair

(UTP), the TRMIM-20R supports voice grade UTP cable as described
in EIA Standard Proposal No. 1907-A. Table 2-1 lists IBM cable
types.

2.1.2 Cable Lengths

The TRMIM-20R is a passive concentrator. It neither regenerates
nor retimes ring signals and the cable lengths used with the
concentrator must consider the Adjusted Ring Length (ARL). ARL
results from recovery processes that attempt to restore continuity to a
broken ring. The ARL is the longest potential ring length, the ring
that would exist following recovery from a failure of the shortest ring
segment trunk cable. Refer to the discussion of token ring concepts
related to ARL in Appendix A. Appendix C describes how to calculate
cable lengths in your network, giving consideration to ARL.

Considering ARL, two cable lengths must be defined: Lobe Length
and Trunk Length. Their combined length defines the path
between two token ring stations and cannot exceed the maximum

drive distance.
Lobe Length - This is the physical length of UTP cable connecting a

station to the trunk coupling unit (TCU) port on the TRMIM-20R.
The recommended maximum length for the longest UTP lobe cable is
shown in Table 2-2. This is a recommended maximum because
cable length calculations for passive ring connections described in
Appendix C could produce a maximum lobe length for your network
that exceeds this limit. However, installing a lobe that exceeds the
recommended maximum should be avoided since it could restrict
future expansion of the network.

Trunk Length - This is the physical length of the STP cabling in the
main ring path, from Ring-Out to Ring-In on each of the attached
token ring devices. The cable budget for the trunk cabling must be
determined by performing the calculations described in Appendix C.
In a totally passive ring (no repeaters or active concentrators, etc. on
the ring), the entire trunk length must be included in calculation of
cable lengths. When only a portion of the ring is passive, the
combined length of the trunk cabling between the passive components
must be considered in the cable length calculations.

Page 2-2

REQUIREMENTS/SPECIFICATIONS

Drive Distance - Drive distance is the limit of reliable signal

propagation without the installation of repeaters in the ring. The
maximum drive distance using Type 1 STP cabling is 770 meters
(2525 feet) at 4 Mbit/sec and 346 meters (1138 feet) at 16 Mbit/sec.
These limits include the combined length of all trunk cables plus
twice the length of the longest lobe cable. (When UTP lobe cables are
used, as with the TRMIM-20R, determining the overall drive distance
requires converting the UTP cable lengths to their Type 1 equivalent
length and then using the Type 1 equivalent to calculate cable
lengths.)

Table 2-1. IBM Cable Types

Type 1 Two shielded twisted pairs (STP) of 22 AWG solid wire

for data. Used for the longest cable runs within the
walls of buildings.

Type 2 Similar to Type 1 data cable, but having four additional

unshielded twisted pairs of 22 AWG solid wire carried
outside of the shield casing. Typically used for voice
communication.

Type 3 Four unshielded twisted pairs (UTP) of 24 AWG solid

wire for data or voice communication. Used for cable
runs in walls of buildings.

Type 5 Two 100/140 µm optical fibers in a single sheath.
Type 6 Two STP of 26 AWG stranded wire for data. This type

is used in patch panels or to connect devices to/from
wall jacks.

Type 8 One flat STP of 26 AWG stranded wire for under carpet

installation.

Type 9 Similar to Type 1, but uses 26 AWG solid wire.

NOTES:

1. Refer to Appendix C for cable conversion factors.

2. Table 2-1 lists all cable types for reference. The TRMIM-20R
supports Type 3 for TCU port cabling and Types 1, 2, 6, and 9 as
trunk cabling.

Page 2-3

REQUIREMENTS/SPECIFICATIONS

Table 2-2. Recommended Maximum Lobe Length

Maximum Lobe Length

4 Mbit/sec 16 Mbit/sec

Voice Grade UTP
(or IBM Type 3) 100 meters 60 meters

2.1.3 Impedance

The characteristic impedance for UTP cable is 100 ohms ±15% and
150 ohms (@ 1 MHz to 20 MHz) ±10% for STP cable.

2.1.4 Attenuation

Attenuation values include the attenuation of the cables, connectors,
and patch panels. Maximum attenuation for UTP cable segments
used with the TRMIM-20R is:

4.0 MHz 16.0 MHz

UTP (Voice Grade) 56 dB/km 131 dB/km
STP (IBM Types 1 & 2) 22 dB/km 45 dB/km
STP (IBM Types 6 & 9) 33 dB/km 66 dB/km

2.1.5 Maximum Number of Stations

The maximum number of stations in a single ring, using UTP cabling,
is 72 stations, regardless of the ring speed.

2.1.6 Crosstalk

Crosstalk is caused by signal coupling between the different cable
pairs contained within a multi-pair cable bundle.

Page 2-4

REQUIREMENTS/SPECIFICATIONS

2.1.7 Noise

Noise can be caused by either crosstalk or externally induced
impulses. If noise induced errors are suspected, it may be necessary
to re-route cabling away from potential noise sources (motors,
switching equipment, high amperage equipment), or to ensure that
the electrical wiring in the area is properly wired and grounded.

2.1.8 Temperature

The attenuation of PVC insulated cable varies significantly with
temperature. At temperatures greater than 40° C (104° F), it is
strongly recommended that you use plenum-rated cables to ensure
that cable attenuation remains within specification. Check the cable
manufacturer’s specifications.

2.2 OPERATING SPECIFICATIONS

This section describes the operating specifications for the
TRMIM-20R. Cabletron Systems, Inc. reserves the right to change
these specifications at any time without notice.

2.2.1 Ring Speed

The TRMIM-20R can be operated at a ring speed of either 4 Mbit/s or
16 Mbit/s. Selection of the ring speed is accomplished either by a
hardware jumper on the TRMIM-20R or by software selection. The
software selection overrides the jumper selection.

2.2.2 Ring Sequence

When multiple token ring boards (set to the same ring speed) are
installed in adjacent slots within an MMAC, they can be attached via
the FNB to create a larger ring network. The default configuration
for the TRMIM-20R attaches boards in adjacent slots automatically
at power on, but the configuration can be modified via network
management software, so that adjacent boards are attached or
detached, resulting in changes in the ring sequence.

Page 2-5

REQUIREMENTS/SPECIFICATIONS

When a TRMIM-20R is installed, the ring sequence starts at the
externally accessible Ring-In port. If the concentrator is detached (by
software, incompatible ring speed or empty adjacent slots) from other
token ring boards, the ring sequence is restricted to the TRMIM-20R
and goes from the Ring-In port to each of the TCU ports, in ascending
port number order, and then out the Ring-Out port.

When multiple token ring boards are installed in consecutive slots
and attached via the FNB, the sequence is in ascending slot number
order. When a concentrator, such as the TRMIM-20R is attached via
the FNB to other token ring boards, the ring sequence begins at the
Ring-In port of the concentrator and is first routed out, via the FNB,
to the next (higher slot number) token ring board on the bus. An
empty slot or non-token ring board causes the FNB trunk connection
to loop back to the first token ring board in the sequence and
continues to thread through the TCU ports and token ring boards
until it returns to the concentrator. There, it threads through the
TCU ports and finally to the Ring-Out port.

Example: TRMIM-22 in slot 1 with ports 2, 5, 8, & 12 in use.

TRMIM-20R in slot 2 with ports 1, 2, 3, 5, and 6 in use.
TRMIM-12 in slot 3 with ports 1, 5, 7, 11, & 12 in use.
An FNB is installed in the MMAC.
All three boards are attached via the FNB.

The ring sequence for this example is from Slot 2, Ring-In port to the
FNB and Slot 3, ports 1, 5, 7, 11, 12, via the FNB to Slot 1 ports 2, 5,
8, 12; then, returning to Slot 2 ports 1, 2, 3, 5, and 6, then out the
Ring-Out port of the TRMIM-20R.

2.2.3 Connector Types
Trunk Coupling Unit Ports - Ten Female RJ-45 connectors are

located on the front panel of the TRMIM-20R. They are labeled 1
through 10. Figure 2-1 shows the pin layout and signal connections
for these connectors.

Page 2-6

REQUIREMENTS/SPECIFICATIONS

-45

g)

TCU Ports: Pin Pin

1 No Connection 5 RX–
2 No Connection 6 TX+
3 TX– 7 No Connection
4 RX+ 8 No Connection

Tx+

Rx­Rx +

Tx-

8
7

6
5

FEMALE RJ

4
3
2
1

Figure 2-1. Trunk Coupling Unit RJ-45 Pinout

STP Trunk Connections - Two Female DB-9 connectors for
attaching STP trunk cables are located on the lower left side of the
TRMIM-20R front panel. Figure 2-2 shows the signal and pin
assignments for the STP ring interface.

Trunk Port: Pin Pin

Ring-In 1 RX– (Main Ring) 5 TX– (Backup Ring)

2 Ground 6 RX+ (Main Ring)
3 Ground 7 Ground
4 Ground 8 Ground

9 TX+ (Backup Ring)

Ring-Out 1 TX– (Main Ring) 5 RX– (Backup Ring)

2 Ground 6 TX+ (Main Ring)
3 Ground 7 Ground
4 Ground 8 Ground

9 RX+ (Backup Ring)

FEMALE DB-9 RECEPTACLE

(Main Ring) RX-

Common

Ground

(Backup Ring) TX-

RING- IN RING-OUT

FEMALE DB-9 RECEPTACLE

1
2
3

4
5

6

RX+ (Main Ring)

7

Common

Ground

8

TX+ (Backup Ring)

9

(Main Ring) TX-

Common

Ground

(Backup Ring) RX-

1
2
3

4
5

Figure 2-2. Trunk Cable Connections

TX+ (Main Ring)

6
7

Common

Ground

8

RX+ (Backup Rin

9

Page 2-7

REQUIREMENTS/SPECIFICATIONS

G

Trunk Wrap Connector - Two male wrap plugs are provided with
each TRMIM-20R. The TRMIM-20R does not automatically wrap.
When no external trunk cable is attached at either ring port (Ring-In/
Ring Out), or if a ring port must be wrapped without using
management software, a wrap plug must be attached to the
appropriate ring port. The wrap plug connects the primary and
backup rings. Figure 2-3 shows the wiring for the wrap plug.

PRIMARY RING

1
2
3
4
5

6
7
8
9

BACKUP RIN

Figure 2-3. Trunk Wrap Plug

2.2.4 LANVIEW LEDs

There are a number LANVIEW LEDs on the front panel of the
TRMIM-20R. The exact locations and functions for these LEDs are
illustrated in Figure 2-4.

16 Mb (Yellow)

TRMIM-20R

SN

7

8
9

10

R I
RO

7
X

16Mb

A
T
T
A
C
H
E
D

ERR

A

1

T

2

T
A

3

C
H

4

E
D

5
6

1

X

RING-IN/RING-OUT (GREEN - 2)

ERR (Red)

ATTACHED (GREEN - 10)

Figure 2-4. TRMIM-20R LANVIEW LEDs

Page 2-8

REQUIREMENTS/SPECIFICATIONS

Table 2-3. LANVIEW LEDs

Label Color Description

16 Mb Yellow Ring Speed Indicator

ON TRMIM-20R is set for 16 Mbit/sec
OFF TRMIM-20R is set for 4 Mbit/sec

RI/RO Green Ring-In/Ring-Out Status (2)

ON Respective ring port is in a non-wrap state
OFF Respective ring port is in a wrap state

ERR Red ON TRMIM-10R hardware error detected

OFF Normal operation

Attached Green Link Attached (10 - One for each TCU port)

ON The respective port is inserted into the

ring.

OFF The respective port is removed (bypassed)

from the ring.

2.2.5 General Specifications

SAFETY

WARNING: It is the responsibility of the person who sells the
system to which the TRMIM-20R will be a part to ensure that the
total system meets allowed limits of conducted and radiated
emissions.

This equipment is designed in accordance with UL478, UL910,
NEC 725-2(b), CSA, IEC, TUV, VDE Class A, and meets FCC
part 15, Class A limits.

SERVICE

MTBF (MHBK-217E)> 109,471 hrs.
MTTR < 0.5 hr.

Page 2-9

REQUIREMENTS/SPECIFICATIONS

PHYSICAL

Dimensions 13.4D x 11.5H x 2.0W inches

(34.0D x 29.2H x 5.1W centimeters)
(includes front panel)

Weight 2 lbs. 2 oz.

(963.9 grams)

Page 2-10

INSTALLING THE TRMIM-20R

CHAPTER 3

INSTALLING THE TRMIM-20R

This chapter contains instructions for installing the TRMIM-20R into
a Cabletron Systems’ MMAC. Instructions for connecting a Twisted
Pair Segment to the MIM for operation are also included. Check that
all requirements listed in Chapter 2, Installation Requirements/

Specifications, are met before installing the MIM.

3.1 UNPACKING THE TRMIM-20R

Prior to installation, you should visually inspect the MIM. Perform
the following steps to unpack the MIM:

1. Carefully remove the MIM from the shipping box. Save the box
and materials in the event the unit has to be repackaged and
shipped.

CAUTION: The electronic components on the MIM are sensitive
to electrostatic discharges (ESD). Observe all ESD prevention
measures when handling the MIM. Static discharges will damage
the MIM.

2. Remove the MIM from its protective plastic bag, holding only the
edges of the MIM or the metal front panel. Avoid touching the
components or the surface of the MIM. Set the MIM on top of its
protective bag in a static free area to prevent the MIM from being
damaged.

Contact Cabletron Systems Technical Support immediately if any
problems exist.

Page 3-1

INSTALLING THE TRMIM-20R

3.2 INSTALLING THE TRMIM-20R INTO THE MMAC

The TRMIM-20R is designed to be easily installed into an MMAC
product When you install the TRMIM-20R, the following guidelines
must be followed:

• The TRMIM-20R cannot be installed into Slot 0. Slot 0 is
reserved for an IRM (Intelligent Repeater Module).

• To hardware daisy-chain several Token Ring MIMs in one
MMAC, be sure that a Flexible Network Bus backplane is
installed in the MMAC. If the Flexible Network Bus backplane is
not installed, each MIM will form its own independent ring
network.

• If the TRMIM-20R is being installed into an MMAC-8FNB, be
sure that a Power Supply Module (PSM or PSM-R) is installed in
the associated rear power supply slot. The PSM or PSM-R is the
source of power for MMAC modules. One PSM or PSM-R is
required for every two MIMs.

NOTE: The PSM-R is a Redundant Power Supply Module, that is
recommended for use with the MMAC-8FNB.

Install the TRMIM-20R into the MMAC as follows:

1. Position the hardware jumper on the proper pins on the
TRMIM-20R to select either 4 or 16 Mbit/sec network ring speed
(see Figure 3-1). Use the specification criteria mentioned in
Chapter 2, Installation Requirements/Specifications, to
decide which speed to use.

NOTE: The network speed is also selectable by software. The
software selection overrides the hardware jumper selection.

2. Power the MMAC chassis off, if it is not already powered off, by
unplugging the AC power cord from the wall outlet.

3. Remove the selected blank panel from the MMAC and slide the
TRMIM-20R (see Figure 3-2) into the MMAC card cage. Be sure
that the card is in the top and bottom slots of the case.

Page 3-2

INSTALLING THE TRMIM-20R

les

rd

Ten RJ-45 Connectors
(Six on mother board, and four on daughter board)

4 Mbit/sec

x x x

16 Mbit/sec

x x x

Network Speed Jumper

J1

...

J1

Mother board

Daughter board

Front
Panel

Two DB-9 Receptac

on the Daughter Boa

Figure 3-1. Network Speed Jumper

4. Secure the module to the MMAC by tightening the knurled
knobs. Failure to firmly secure the MIM may result in improper
operation.

5. Power the MMAC chassis on.

Figure 3-2. Installing the TRMIM-20R

Page 3-3

INSTALLING THE TRMIM-20R

-9

3.3 CABLING THE TRMIM-20R

Prior to connecting cables, check that the the pinout and maximum
cable lengths throughout the system conform to the requirements
described in Chapter 2, Installation Requirements/
Specifications.

Since the TRMIM-20R uses differential Manchester encoding, the
trunk coupling unit (TCU) and Ring-In/Ring-Out trunk ports are not
sensitive to signal polarity. If the (+) and (-) lines within a pair are
reversed, the network will still function properly. Operating in this
condition is not recommended and, when discovered, the cable
connections should be corrected according to the information provided
in Chapter 2, Installation Requirements/Specifications.

3.3.1 Lobe Cabling

The physical lobe connection (see Figure 3-3) from the TRMIM-20R to
the token ring station does not require the use of a crossover cable.
The TCU and token ring station connectors are wired such that the
transmit pair from the TRMIM-20R connects to the receive pair of the
station and the receive pair from the TRMIM-20R connects to the
transmit pair of the station. This provides the necessary signal
crossover or Null Modem Effect. The Type 3 Media Filter provides
impedance matching from the Type 3 (UTP) lobe cabling to the Type 1
(STP) interface provided with many token ring stations.

The twisted pair segment from the TRMIM-20R can be connected to
any Token Ring station.

TCU Port

6

3

4

5

Lobe Cable

TX+

TX–

RX+

RX–

RX+

RX–

TX+

TX–

RJ-45

Token Ring Station

6

3

TYPE 3
MEDIA
FILTER

4

5

RX+

6

RX–

1

9

TX+

5

TX–

DB

Figure 3-3. UTP Connections

Page 3-4

INSTALLING THE TRMIM-20R

Attaching UTP Lobe Cables to the TRMIM-20R

To attach a UTP lobe cable to the TRMIM-20R:

1. Connect the male RJ-45 connector from one end of the UTP lobe
cable to a port on the TRMIM-20R (see Figure 3-4).

2. If a patch panel is to be used, connect the other end of the cable
to the appropriate patch panel jack. (Install RJ-45 to MIC
adapters as needed.)

3. Repeat this process for each station

Attaching the UTP Cable at the Station

A Type 3 Media Filter must be installed at the station end of the lobe
cable. Some stations incorporate an internal filter and do not require
any additional equipment. If your station requires an external Type
3 Media Filter, install the filter between lobe cable and station port.
Otherwise, connect the stations to the wall plate using a Type 3 patch
cable. Attach one end of the patch cable to the wall plate and the
other to the station port.

Page 3-5

INSTALLING THE TRMIM-20R

K

G

3.3.2 Trunk Cabling

The TRMIM-20R Ring-In/Ring-Out ports support STP trunk cable
connections. The physical trunk connections, for both the Ring-In
and Ring-Out ports (see Figure 3-4), consist of two pairs of wire: a
transmit signal pair (TX+, TX-) and a receive signal pair (RX+, RX-).
The transmit pair at the TRMIM-20R Ring-Out port interfaces with
the primary ring path and at the Ring-In port interfaces with the
backup ring path. Similarly, the receive pair at the Ring-In port
interfaces with the primary ring path and, at the Ring-Out port,
serves the backup path.

Figure 3-4. STP Trunk Connections

TRMIM-20R

RING-IN

PORT

RX+

RX–

TX+

TX–

TX+

TX–

RX+

RX–

RING-OUT

PORT

Male DB-9

Connector

6

1

9

5

6

1

9

5

RED

GREEN

ORANGE

BLACK

RED

GREEN

ORANGE

BLACK

Male DB-9

Connector

PRIMARY

RING PATH

BACKUP

RING PATH

PRIMARY

RING PATH

BACKUP

RING PATH

FROM

PREVIOUS

TOKEN

RING

DEVICE

STP TRUN

CABLIN

TO

NEXT

TOKEN

RING

DEVICE

Page 3-6

INSTALLING THE TRMIM-20R

The STP trunk cables are attached to the TRMIM-20R using male
DB-9 connectors. If a patch panel is to be used, connect Ring-In from
the patch panel to Ring-In of the TRMIM-20R and Ring-Out from the
patch panel to Ring-Out on the TRMIM-20R. When connections are
made between concentrators within the same closet, daisy-chain the
connections, Ring-In to Ring-Out, from concentrator to concentrator.
For some installations, DB-9 to MIC adapters may be needed.

NOTE: Wrap Jumper Plugs must be used for installations with no
external ring connections to the TRMIM-20R or to replace a trunk
cable to bypass a failed ring segment. Two plugs are provided with
each TRMIM-20R.

3.4 FINISHING THE INSTALLATION

Page 3-7

INSTALLING THE TRMIM-20R

Complete the installation by doing the following:

1. Ensure the MMAC and the stations are powered on.

2. Ensure that all LEDs on the MIM and any LEDs on the stations
are illuminated properly, with no error conditions shown. If they
are not in a normal condition, proceed to Chapter 4, Testing and
Troubleshooting.

The green Link Attached LEDs on the MIM should be illuminated
for each station inserted into the ring. The yellow 16Mb LED
should only be on if 16 Mbit/s ring speed is selected.

3. Configure the networking software.

The TRMIM-20R is now ready for operation. Before placing the
network into service, test the installation thoroughly, making sure
that all stations are able to be addressed and that the data is being
relayed without error. Ensure that the networking software is
configured properly to match the installed network.

Page 3-8

TESTING AND TROUBLESHOOTING

CHAPTER 4

TESTING AND TROUBLESHOOTING

This section contains procedures to verify the cabling connecting the
TRMIM-20R to the Token Ring network and any attached stations. A
description of LANVIEW and its function in troubleshooting physical
layer network problems is also provided.

4.1 INSTALLATION CHECKOUT

Perform the following steps to check the installation of the
TRMIM-20R:

1. Be sure that the Token Ring stations and the MMAC match the

AC power source (120 Vac or 240 Vac) and are powered on.

2. Trace the ring path through the network, to be sure that there

are no breaks in the ring and that it is free from logical design
errors. While tracing the ring:

a. Check each cable connection on the MIM.
b. Verify that the pinout for every connector is correct.
c. Check the cable conductors for continuity. Cable testers are

available for this task.

d. Check each cable connection at patch panels and wall plates.

3. Check the network ring speed:

a. Check that the ring speed matches the station and cable

specifications mentioned in Chapter 2, Installation
Requirements/Specifications.

b. Verify all devices on the ring network are set to the same ring

speed. Check all MIMs and stations in the network.

Page 4-1

TESTING AND TROUBLESHOOTING

4. Verify that the maximum number of stations and maximum cable
lengths for EACH station are not exceeded.

When these checks have been successfully completed for each
connection to the TRMIM-20R, the MIM is ready for normal
operation. If further problems occur, contact Cabletron Systems
Technical Support.

4.2 USING LANVIEW

LANVIEW is Cabletron Systems’ built-in visual diagnostic and status
monitoring system. Using LANVIEW, your network troubleshooting
personnel can quickly scan the LANVIEW LEDs to observe network
status or diagnose network problems, and determine which node or
segment is faulty. The definitions and locations for the front panel
LANVIEW LEDs are illustrated in Figure 4-1.

16 Mb (Yellow)
ON - Ring speed is set for 16 Mbit/sec.
OFF - Ring speed is set for 4 Mbit/sec.

ERR (Red)

TRMIM-20R

SN

A

A

7

T

T

8

T

T

A

A

9

C

C

H

H

10

E

E

R I

D

D

RO

7
X

ERR16Mb

1
2
3
4
5
6

1
X

ON - A hardware error has occurred.
OFF - Normal operation

ATTACHED (Green - 10)
ON - This station is inserted into the ring.
OFF - This station is removed from the ring.

RING-IN/RING-OUT Port Status (Green - 2)
ON - Respective Ring-In/Ring-Out Port
is in a non-wrap state.
OFF - Respective Ring-In/Ring-Out Port
is in a wrap state

Figure 4-1. TRMIM-20R LANVIEW LEDs

Page 4-2

TESTING AND TROUBLESHOOTING

• 16 Mb - The Ring Speed LED (Yellow) is lit to indicate that the

TRMIM-10R ring speed is set to 16 Mbit/sec. When this indicator
is not lit, the ring speed is set to 4 Mbit/sec. The ring speed is set
to a default setting by hardware jumper, J1 (refer to Chapter 3,
Installing the TRMIM-20R, for setting this jumper). The
TRMIM-20R is set to the default ring speed at power on. The ring
speed can be changed via local network management software.

• RI/RO Status - The ring status indicators (2, Green) indicate the

state of the Ring-In and Ring-Out ports. The normal condition is
lit, indicating that the respective ring port is in a non-wrap state.
When either indicator is not lit, it indicates that the respective
ring port has been set to the wrap state by network management
software. (The TRMIM-20R does not automatically wrap to
recover from ring segment failure.)

• ERR - The error indicator (Red) should not be lit under normal

operating conditions. When lit, this LED indicates the detection
of a TRMIM-20R hardware failure. If the problem persists,
contact Cabletron Systems Technical Support.

• Attached - Ten Attached LEDs (Green), one for each TCU port

indicate that the station attached to the respective TCU port is
powered on and inserted into the ring. When an Attached LED is
not lit, the respective port is inactive, and the station is removed
(bypassed) from the ring.

Page 4-3

BASIC TOKEN RING NETWORKS

APPENDIX A

BASIC TOKEN RING NETWORKS

This Appendix covers the basic operation and concepts related to
design considerations for token ring networks.

A.1 BASIC TOKEN RING OPERATION

A token ring network is made up of a number of stations electrically
connected to form a continuous loop. Physically, the stations are
usually arranged in a star pattern around a hub or concentrator
module. The hub or concentrator provides ring access for several
stations that are electrically (or optically in the case of fiber optic
media) attached to the ring. The connections at the hub form wiring
drops, called lobes, that extend out to each of the attached stations
and return to the hub (see Figure A-1).

STATION 3

STATION 2

STATION 1

STATION 8

Figure A-1. Typical Token Ring Physical Installation

HUB

STATION 7

STATION 4

STATION 5

STATION 6

Page A-1

BASIC TOKEN RING NETWORKS

Basic Token Ring Protocol

This summary briefly covers a basic subset of the overall token ring
access protocol. The IEEE Standard 802.5 provides greater detail on
token ring access methods and should be referenced whenever more
complete information is needed.

Each station attached to the ring is identified by a unique station
address differentiating it from all other stations. When a token ring
station is activated and inserted into a ring, several actions are
initiated to maintain order on the ring. All the active stations enter
into a monitor contention dialogue, resulting in one station (the
highest currently active address) establishing itself as the Active
Monitor (AM). As part of its duties, the AM initializes the ring and
transmits a special message frame called a token.

The token circulates around the ring from station to station. Receipt
of the token grants a station the privilege of accessing the ring to
transmit data. When a station receives a token and uses the
opportunity to transmit information, it appears that the token is
removed from the ring and held by the station for the duration of the
transmission. In reality, the token is modified by the station and
used to create the data frame. The token is divided and the
information is inserted between the modified Access Control (AC)
field, and the Ending Delimiter (ED). Figure A-2 shows the token
and information frame formats. Each station receives the token from
a station preceding it on the ring and either uses it while
transmitting data or passes (transmits) it to the next active station on
the ring. When a station has data to transmit, the station modifies
the token AC field, inserts its data into the frame between the AC
and ED, waits for the transmission to circulate completely around the
ring, strips its own data transmission from the ring, and then
restores the token. A Token Holding Timer (THT) controls the length
of time that any station may retain the token. Here is a typical token
ring sequence:

1. AM initiates the ring and places the token on the ring.

2. Station xxx wants to send some data to station yyy. Station xxx

modifies the token by inserting the information addressed to
station yyy.

Page A-2

BASIC TOKEN RING NETWORKS

TOKEN FRAME

3. The frame addressed for yyy circulates around the ring. All

stations in the ring examine the frame, checking the address, in
successive order. When the transmission gets to yyy, station yyy
copies the data as it goes past.

4. When the original transmission finishes the trip around the ring

and is seen by station xxx again, station xxx removes the
transmission from the ring. At this time, if station xxx has no
more data to send or if its Token Holding Time (THT) has
expired, station xxx releases the token back onto the ring.

5. The ring is now available for use by another station. The token

resumes its circulation until it reaches the next station that is
waiting to send data. Here, the process will begin again with
that station seizing the token.

Unless an error occurs that disrupts normal token passing, the
original token remains in circulation. Lost tokens are detected by the
AM and appropriate corrective procedures are initiated.

ACSD ED

INFORMATION FRAME

ACSD ED

DAFC SA FS

Figure A-2. Token Ring Frame Formats

SD - Starting Delimiter (1 octet)
AC - Access Control (1 octet)
FC - Frame Control (1 octet)
DA - Destination Address (2 or 6 octets)
SA - Source Address (2 or 6 octets)
INFO - Information (0 or more octets)
FCS - Frame Check Sequence (4 octets)
ED - Ending Delimiter (1 octet)
FS - Frame Status (1 octet)

INFO

FCS

Page A-3

BASIC TOKEN RING NETWORKS

Early Token Release

Early Token Release (ETR) is a second protocol option presented in
the IEEE 802.5 Standard. ETR is an optional protocol that may be
used with 16 Mbit/sec 802.5 token ring networks. It has the
advantage of increasing the efficiency of the ring by allowing
transmissions from more than one station to occupy the ring at the
same time. This protocol is similar to the basic token ring protocol in
that possession of the token determines the transmitting station, but
with ETR the token is returned to the ring immediately following the
message frame or upon THT expiration. ETR is a function of the
network software and, when used, is usually invoked dynamically in
response to increased network loads.

Expanding the Token Ring

Concentrators, repeaters, converters and bridges are found
throughout token ring networks. They are used to create ring
topologies to meet the specific needs of many different network
applications. Some of these topologies are discussed in Appendix B.
Together with Figure A-3, the following descriptions provide a brief
introduction to these components. The network functions provided by
the following devices are often combined in a single device.

A concentrator is a device that provides multiple trunk coupling
unit ports, bounded by externally accessible Ring-In and Ring-Out
trunk ports. The primary function of a concentrator is to serve as a
hub, providing trunk coupling units for attaching stations and
controlling access to the ring. Each trunk coupling unit port can be
electrically shorted to bypass the attached lobe when a station is
disabled or when the lobe cable is disconnected. A concentrator is
referred to as an Active Concentrator when the Ring-In/Ring-Out
trunk ports provide regeneration and retiming of ring signals.
Passive Concentrators rely on the drive from the transmitting
station to carry a message to its destination. Multiple concentrators
are often linked via their trunk connections to form a single larger
ring.

Repeaters are used when the length of the the main ring must be
extended beyond the drive distance of other components on the ring.
The repeater’s primary role is to regenerate and retime the signals on
the ring. They are often used to connect concentrators together to
form a larger ring. Active concentrators provide the same
regeneration and retiming function as a repeater and some, as in the

Page A-4

BASIC TOKEN RING NETWORKS

case of Cabletron Systems’ Token Ring Repeater (TRRMIM-16),
convert from one media type to another (eg. shielded twisted pair to
fiber optic).

Converters (not illustrated) provide the means for changing from
one media type to another. Usually, the conversion allows a
particular ring segment to cover a greater distance. Converters
typically regenerate and retime signals as part of their functions.

Bridge devices (not illustrated) connect rings that cannot be
expanded (at their maximum number of stations) or rings that are
operating at different speeds (4 Mbit/sec vs. 16 Mbit/sec). They do not
expand a single network, rather they connect multiple networks
together. They maintain routing information, filter messages that
cross the bridge, regenerate signals and provide buffering required for
network synchronization.

MMAC
Chassis

TRMIM-10R

Concentrator #1

Ring-In

Ring-Out

MMAC
Chassis

Ring-Out

MAIN RING

TRRMIM-16

TRC-800

Concentrator #2

Ring-In

Ring-In

Ring-Out

Repeater

TRMIM-12

Figure A-3. Repeaters In a Token Ring

Page A-5

BASIC TOKEN RING NETWORKS

T

Reliability

Since token ring networks depend on ring topology for proper
operation, the entire network is vulnerable to the frailties of each ring
segment. Arranging the ring as a star, using concentrators, and
providing trunk coupling units for the station connections reduce the
risk of a single failing node bringing the entire network down. To
further reduce this vulnerability, a redundant data path is provided
in the main ring trunk cabling.

While our theoretical ring required media capable of only one-way
traffic to achieve the circular flow of data, actual token ring
applications use media that provides two ring paths, a primary ring
and a backup ring. This backup ring is used to restore the continuity
of the ring in the event of a failed trunk segment (broken trunk
cable). Figure A-4 illustrates how the open ends of the ring can be
wrapped into the backup ring, restoring continuity through the
creation of a new ring. (Some devices will wrap automatically when a
problem is detected. Others require human intervention to restore
the ring.) The ability to wrap and bypass trunk segments introduces
other problems. The recovery process produces a much longer
physical trunk cable length. When this length exceeds the maximum
drive distance, the problem must be solved by the network designer
by adjusting cable lengths or installing repeaters in the ring.

RING-IN

Page A-6

RING-OUT

CONCENTRATOR #2

WRAP

RING-OUT

Figure A-4. Wrapping a Broken Ring

RING-IN

CONCENTRATOR #3

PRIMARY RING

BACKUP RING

CONCENTRATOR #1

RING-OU

RING-IN

BASIC TOKEN RING NETWORKS

RS

A.2 DESIGN CONSIDERATIONS

A major design consideration is ring length. The ring propagation
must be long enough to accommodate an entire token (24 bit times)
and still be short enough for the transmitting devices to reliably send
information to the next station. The AM inserts an artificial delay
that prevents the ring from appearing too short. Overly long ring
lengths create a problem as well, but these problems are best solved
through restraints in the network design.

Drive Distance is the limit of reliable signal propagation around the
ring. The cable length between a sending and receiving station must
not exceed the drive distance. The cable lengths that make up the
drive distance include the lobe from the sending station to the
concentrator, the sum of the trunk cable segments around the ring
and, since the sending station must ultimately remove the original
message from the ring, the lobe from the concentrator to the sending
station. Figure A-5 illustrates the cables that make up the drive
distance in a token ring.

50

METERS

CONCENTRATOR #3

CONCENTRATOR #2

150

75

METERS

DRIVE DISTANCE
LOBE CABLING
TRUNK CABLING

CONCENTRATOR #1

LONGEST LOBE

(150 METERS)

METE

Figure A-5. Cable Lengths in a Token Ring

When a wrap occurs that bypasses the shortest segment of trunk
cable on the ring, it produces a “worst case” ring length referred to as
the Adjusted Ring Length (ARL). Since the lobe is easily bypassed
by the concentrator’s trunk coupling units, lobe cabling does not
provide a backup path. Consequently, a wrap affects only the main
ring (trunk cables). The lobe cable length is not included in the ARL.

Page A-7

BASIC TOKEN RING NETWORKS

RS

ARL is calculated by combining the lengths of all the trunk cables,
subtracting the length of the shortest trunk cable (typically an 8-foot
patch cable within a wiring closet) and then doubling the result (Lobe
cabling is not part of the ARL calculation). The impact of ARL on
drive distance is apparent when we examine the resulting calculation
for drive distance. The ARL plus the Longest Lobe Length is now the
maximum drive length. This maximum drive length is the limit of
reliable data transmission. (Appendix C provides procedures and
tables to assist in calculating cable lengths, giving consideration to
ARL.)

Figure A-6 shows the impact of a broken trunk segment on overall
ring length. Without the break, the ring length is 275 meters and the
drive distance for the station at the longest lobe is 575 meters (275 +
(2 x 150)). With the 50-meter section of trunk cable between
Concentrator #2 Ring-Out and Concentrator #3 Ring-In broken, the
two ring ports must be wrapped, connecting the primary ring to the
backup ring, and bypassing the broken trunk cable. In this condition,
the ring length increases from 275 meters to 450 meters (2 x (75 +

150)) and the drive distance becomes 750 meters.

75

METERS

Page A-8

RING-OUT

CONCENTRATOR #2

50

METERS

WRAP

CONCENTRATOR #1

Figure A-6. Adjusted Ring Length

RING-IN

CONCENTRATOR #3

PRIMARY RING

BACKUP RING

LONGEST LOBE

(150 METERS)

150

METE

APPLICATIONS

ith

APPENDIX B

APPLICATIONS

This Appendix presents the following network applications as
examples of how the TRMIM-20R may be used in a token ring
network. These are examples to help clarify features and
applications for the TRMIM-20R and actual applications are NOT
limited to those shown here.

• Adding to an existing Token Ring Network

• Separate Token Ring Networks in One MMAC

• Token Ring Networks Bridged Together

• MMAC with Ethernet and Token Ring Operating Simultaneously

B.1 ADDING TO AN EXISTING TOKEN RING NETWORK

Figure B-1 shows the addition of an MMAC with a TRMIM-22 and a
TRMIM-20R into an existing token ring network. Here, the
TRMIM-20R is used to insert an MMAC and its token ring products
into the ring. Any concentrator (with externally accessible trunk
ports) designed for use in an MMAC can be used. The Ring-In and
Ring-Out ports of the TRMIM-20R are connected to Ring-In and Ring­Out ports of the adjacent concentrators. The existing token ring
network could consist of many vendors’ products.

Ring-In

MMAC
Chassis

Figure B-1. Adding to an Existing Ring Network

Concentrator #1

Ring-Out / Ring-In

Ring-Out

TRMIM-20R

TRMIM-22

Concentrator #2

Ring-In

Ring-Out

Token Ring Network with two
concentrators and one MMAC w
TRMIM-20R and TRMIM-22.

Page B-1

APPLICATIONS

B.2 SEPARATE TOKEN RING NETWORKS IN ONE MMAC

Figure B-2 shows three independent Token Ring Networks within the
same MMAC-8. The MMAC-8 has eight slots. The IRM occupies slot
0, leaving seven slots available for network boards. Cabletron
Systems’ token ring products are recognized on the MMAC-8FNB
Flexible Network Bus (FNB) backplane by a unique identifier. If an
FNB is installed, when the MMAC is powered on, all the adjacent
token ring MIMs set to the same ring speed will be automatically
linked together forming a single larger ring network. If several
independent ring networks are desired, the configuration must be set,
via the local (IRM) management console, so as to isolate specific
MIMs. MIMs set to different ring speeds (e.g. one at 4 Mbit/sec and
one at 16 Mbit/sec) cannot be linked together.

Example:

MMAC-8FNB, one TRMIM-20R, one TRMIM-22,
five TRMIM-12s and one IRM.
Slot 0 IRM
Slot 1 TRMIM-20R for ring network #1 at 4 Mbit/sec
Slot 2 TRMIM-22 for ring network #1 at 4 Mbit/sec
Slot 3 first TRMIM-12 for ring network #2 at 4 Mbit/sec
Slot 4 second TRMIM-12 for ring network #2 at 4 Mbit/sec
Slot 5 first TRMIM-12 for ring network #3 at 16 Mbit/sec
Slot 6 second TRMIM-12 for ring network #3 at 16 Mbit/sec
Slot 7 third TRMIM-12 for ring network #3 at 16 Mbit/sec

Page B-2

MMAC-8FNB

Token Ring Network #3
made up of three TRMIM-12s
at 16 Mbit/sec.

Token Ring Network #1 made up of
a TRMIM-20R and one TRMIM-22
running at 4 Mbit/sec.

Token Ring Network #2
made up of two TRMIM-12s
at 4 Mbit/sec.

NOTE:
Management software can be used
to control the ring speed and linking
of Token Ring Network Boards.

Figure B-2. Several Independent Ring Networks

in One MMAC-8FNB

APPLICATIONS

B.3 TOKEN RING NETWORKS BRIDGED TOGETHER

Figure B-3 illustrates the bridging of two token ring networks
together using a token ring to token ring network bridge. Bridging
ring networks is necessary when: the networks are of different ring
speeds (one at 4 Mbit/sec and the other at 16 Mbit/sec), or when there
is a need for networks to be connected and one or both of the rings is
at maximum capacity. In Figure B-3, one network is running at
4 Mbit/sec and the other is running at 16 Mbit/sec. The 16 Mbit/sec
ring network with 130 stations is close to its maximum capacity of
136 stations. When the two networks are connected, the bridge is
counted as a station in both rings.

Token Ring Network
running at 16 Mbit/s

135 stations maximum
plus the bridging device

Token Ring Network
running at 4 Mbit/s

249 stations maximum
plus the bridging device

TOKEN RING

TO

TOKEN RING

BRIDGE

Figure B-3. Using a Bridge to Connect Ring Networks

Page B-3

APPLICATIONS

B.4 MMAC WITH ETHERNET AND TOKEN RING

SIMULTANEOUSLY

Figure B-4 illustrates the simultaneous installation of an Ethernet
network with a token ring network in the same MMAC. To connect
the two networks together requires a token ring to Ethernet bridge.
Without this bridge, information cannot pass between the two
networks. In this illustration the Ethernet and token ring networks
are not able to communicate with each other.

Ethernet Network

T

T

T

AUI Cable

MMAC-8FNB
with IRM,
THN-MIM, and
TRMIM-12.

Since the Ethernet
and Token Ring
Networks are NOT
Bridged together by
a bridging device,
they can NOT share
data.

Token Ring Network

Figure B-4. Token Ring and Ethernet in the Same MMAC

Page B-4

CALCULATING RING LENGTH

APPENDIX C

CALCULATING RING LENGTH

This Appendix presents methods for calculating cable lengths for
passive token ring networks or passive network segments giving
consideration to adjusted ring length (ARL). These calculations
differ between networks that are wholly contained within a single
wiring closet and networks spanning multiple wiring closets.
This appendix describes both network configurations. Be sure to use
the tables and instructions that apply to your network’s wiring when
calculating the cable lengths.

A subsection titled Formulas follows the cable length calculations.
These formulas are presented as a source of additional reference
information. They show how the tables on the Cable Length
Worksheets were compiled and are NOT needed for calculating your
cable lengths.

Chapter 2, Requirements/Specifications, lists information related
to the maximum lobe length, maximum drive distance, and
specifications for various cable types that can be used with your
Cabletron Systems’ token ring products. Refer to that chapter
whenever you have a question about recommended cable types or
maximum cable lengths.

C.1 RULES FOR CALCULATING CABLE LENGTHS

Several rules must be followed when using the tables and
instructions for ARL. They define the cable types and cable lengths
used for various segments of your token ring network.

Rules:

• Internal closet trunk cabling is Type 6 in the following lengths:

- 8 feet - Trunk coupling unit port to patch panel

- 8 feet - Patch panel to concentrator ring ports

- 8 feet - Concentrator to concentrator

- 30 feet - Rack to Rack.

Page C-1

CALCULATING RING LENGTH

• Wherever Type 6 or Type 9 cable is used, the length must be

converted to the equivalent Type 1 cable length as follows:

(Length of Type 6 or 9 cable) x 3/2 =

Equivalent Type 1 or 2 length

C.2 SINGLE WIRING CLOSET NETWORKS

In a single wiring closet application, all of the trunk cabling is
contained inside the closet, and the cable length of interest is the
longest lobe length (the cabling between the concentrator’s TCU
port and the most distant Token ring station). Use the UTP Cable
Length Worksheet, Single Wiring Closet form at the end of this
section to calculate your longest lobe cable length. Choose the column
that matches your ring speed and complete the worksheet as follows:

1. The Maximum Drive Limit, when considering ARL, is one-half
the maximum drive distance (2525 feet at 4 Mbit/s or 1138 feet at
16 Mbit/s) or 1263 feet at 4 Mbit/s or 569 feet at 16 Mbit/s for
Type 1 STP cable.

2. Refer to the table at the bottom of the worksheet to find the
Internal Trunk Length for your wiring closet configuration.

3. Subtract the Internal Trunk Length from the Maximum
Drive Limit to obtain the Type 1 Cable Budget:

Type 1 Cable Budget =

Maximum Drive Limit – Internal Trunk Length

4. Since we are trying to determine the UTP Lobe Length for your
network, the Type 1 Cable Budget must be converted to a
Maximum UTP Cable Length using a conversion factor of .39
for networks operating at 4 Mbit/s or by .34 for 16 Mbit/s.

5. Multiply the Type 1 Cable Budget by the conversion factor.

Type 1 Cable Budget x (.39 or .34) =

Maximum UTP Lobe Length

Page C-2

CALCULATING RING LENGTH

6. Determine your Actual Longest Lobe length, combine:

TCU port to patch panel feet
Wiring closet to wall plate + feet
Wall plate to station + feet

Longest Lobe Length

7. Compare the Maximum UTP Lobe Length, calculated in step

5, with your networks longest lobe, from Step 6. If your Actual
Longest Lobe exceeds the Maximum UTP Lobe Length
(negative result in step 7), you must adjust your lobe length or
add active components (repeaters) to extend the available trunk
cable length.

I f you need further assistance with your network design, contact
Cabletron Systems Technical Support.

Use Figure C-1 to follow the calculations using the UTP Cable Length
Worksheet for Single Wiring Closets in this example for a 4 Mbit/sec
ring:

Single Wiring Closet 4 Mbit/sec

1. Maximum Drive Limit 1. 1263 ft.

2. Internal Trunk Length
(7 concentrators in 2 racks = 150') 2. – 150 ft.

3. Type 1 Cable Budget 3. 1113 ft.

4. Type 1 STP to UTP Conversion 4. X .39

5. Maximum UTP Lobe Length 5. 434 ft.

6. Actual Longest Lobe (Station 2)
(8' x 3/2) + 185' + (30 x 3/2) = 242' 6. – 242 ft.

7. Result 7. 192 ft.

The result is positive and no repeaters or cable adjustments are
needed.

Page C-3

CALCULATING RING LENGTH

STATION 1

WALL
PLATE

150'

UTP LOBE CABLING

STP TRUNK CABLING

8'

8'

8'

30'

30'

185'

WALL
PLATE

WIRING CLOSET

Figure 6-1. Wiring in a Single Wiring Closet

Formulas

Two formulas were used to create the tables for the UTP Cable
Length Worksheets. The first defines the cabling for a single
wiring closet with only one rack and the second for multiple racks
within the wiring closet. The difference between the two
formulas is accounted for by the cabling between the racks within
a wiring closet. The term Internal Trunk Length refers to the
trunk cable length within the wiring closet, adjusted to give
consideration to ARL. The actual calculations used in the table
are as follows:

STATION 2

Page C-4

CALCULATING RING LENGTH

Single Rack

Internal Trunk Length =

(Concentrator to Concentrator Patch Cables)

where:

Concentrator to Concentrator Patch Cables =

12' x number of Concentrators (see note)

NOTE: Wrap plugs must be installed if no external trunk cabling

is connected at the TRMIM-20R ring ports.

Multiple Rack

Internal Trunk Length =

(Rack to Rack Patch Cables +

Concentrator to Concentrator Patch Cables)

where:

Rack to Rack Patch Cables = 45' x number of Racks

Concentrator to Concentrator Patch Cables =

12' x (number of Concentrators - number of Racks)

NOTE: You are hereby authorized to copy the next page (UTP Cable

Length Worksheet) in this appendix. Copy the worksheet for your
planning needs, but remember to keep a blank copy for future network
configuration changes.

Page C-5

CALCULATING RING LENGTH

UTP CABLE LENGTH WORKSHEET

Single Wiring Closet

1. Maximum Drive Limit

(1263 feet for 4 Mbit/s or 569 feet for 16 Mbit/s)

2. Internal Trunk Length

(Value from Table below)

3. Type 1 Cable Budget

(1) – (2) = (3)

4. Type 1 STP to UTP Conversion

(.39 for 4 Mbit/s or .34 for 16 Mbit/s)

5. Maximum UTP Lobe Length

6. Actual Longest Lobe

7. If you get a negative result, adjust
cable lengths or add active
components to the ring.

4 Mbit/sec 16 Mbit/sec

1.

2. – ft.

3. ft.

4.

5.

6. ft.

7.

1263 ft.

X

.39

–

1.

2. – ft.

3. ft.

X

4.

5.

ft.

6. ft.

–

7.

569 ft.

.34

ft.

Internal Trunk Length for a Single Wiring Closet

Number of Number of Racks (Single Closet)

Concentrators 12345 6 7 8910

1 12
2 24 90 Values are Type 1
3 36 102 135 Equivalent in feet
4 48 114 147 180
5 60 126 159 192 225
6 72 138 171 204 237 270
7 84 150 183 216 249 282 315
8 96 162 195 228 261 294 327 360

9 108 174 207 240 273 306 339 372 405
10 120 186 219 252 285 318 351 384 417 450
11 132 198 231 264 297 330 363 396 429 462
12 144 210 243 276 309 342 375 408 441 474
13 222 255 288 321 354 387 420 453 486
14 234 267 300 333 366 399 432 465 498
15 246 279 312 345 378 411 444 477 510
16 258 291 324 357 390 423 456 489 522
17 270 303 336 369 402 435 468 501 534
18 282 315 348 381 414 447 480 513 546
19 294 327 360 393 426 459 492 525 558
20 306 339 372 405 438 471 504 537 570

Page C-6

CALCULATING RING LENGTH

C.3 MULTIPLE WIRING CLOSET NETWORKS

In multiple wiring closet applications, both external trunk cable
length and lobe cable length must be considered in the overall drive
distance for a passive ring. Use the UTP Cable Length
Worksheet, Multiple Wiring Closet form toward the end of this
section to determine the cable lengths that can be used in multiple
wiring closet token ring applications. Choose the column that
matches your ring speed and complete the worksheet as follows:

1. Determine your Actual Longest Lobe length, by combining:
TCU port to patch panel feet

Wiring closet to wall plate + feet
Wall plate to station + feet

Longest Lobe Length

2. Since we are trying to establish a budget for Type 1 STP trunk

cabling, the UTP Lobe Length for your network (Actual

Longest Lobe) must be converted to an Equivalent Type 1
Lobe Length using a conversion factor of 2.54 for networks

operating at 4 Mbit/s or by 2.91 for 16 Mbit/s.

3. Multiply the Actual Longest Lobe by the conversion factor.

Actual Longest Lobe x (2.54 or 2.91) =

Equivalent Type 1 Lobe Length

4. Refer to the table at the bottom of the worksheet to find the

Internal Trunk Length for each Wiring Closet (WC) in the
multiple closet configuration. Add these values to find the total
Combined Trunk Length:

WC-1 + WC-2 + WC-n = Combined Trunk Length

Page C-7

CALCULATING RING LENGTH

5. Add the Equivalent Type 1 Lobe Length (step 3) to the
Combined Trunk Length (step 4) to find the Internal Drive
Distance, and enter the sum here and on line 4a.

Internal Drive Distance =

Combined Trunk Length + Actual Longest Lobe

6. The Maximum Drive Limit, when considering ARL, is one-half
the maximum drive distance (2525 feet at 4 Mbit/s or 1138 feet at
16 Mbit/s) or 1263 feet at 4 Mbit/s or 569 feet at 16 Mbit/s for STP
cable.

7. Subtract the Internal Drive Distance (step 5) from the

Maximum Drive Limit to obtain cable length available for the
External Trunk Cable Budget (outside the closets) in your

configuration:

External Trunk Cable Budget =

Maximum Drive Limit - Internal Drive Distance

8. Find the total length of the Actual Trunk Cable lengths
between wiring closets.

9. Compare the Actual Trunk Cable length with the External

Trunk Cable Budget (step 7). When your Actual Trunk
Cable length exceeds the External Trunk Cable Budget

(negative result in step 9), you must either adjust your lobe/trunk
lengths or add active components (repeaters) to extend the
available trunk cable length.

If you need further assistance with your network design, contact
Cabletron Systems Technical Support.

Page C-8

CALCULATING RING LENGTH

Use Figure C-2 to follow the calculations using the UTP Cable Length
Worksheet for Multiple Wiring Closets in the following example of a 4
Mbit/sec ring.

Example:

Multiple Wiring Closet 4 Mbit/sec

1. Actual Longest Lobe (given as 85 feet) 1. 85 ft.

2. UTP to Type 1 STP Conversion 2. X 2.54

3. Equivalent Type 1 Lobe Length 3. 216 ft.

4. Combined Trunk Length
93' + 69' + 24' = 186' 4. + 186 ft.

5. Internal Drive Distance 5. 402 ft.

6. Maximum Drive Limit 6. 1263 ft.
6a. Internal Drive Distance – 402 ft.

7. External Trunk Cable Budget 7. 861 ft.

8. Actual External Trunk Cable Length
95' + 70' + 175' = 340' 8. – 340 ft.

9. Result 9. 521 ft.

The result is positive and no repeaters or cable adjustments are
needed.

Page C-9

CALCULATING RING LENGTH

70'

95'

WC-1
2 Racks

Token Ring Corporation

4 Concentrators
93 feet

WC-2
2 Racks
2 Concentrators
69 feet

85'

175'

WC-3
1 Rack
1 Concentrator
24 feet

LONGEST

LOBE

Figure C-2. Building Cable Budget

Formulas

The formulas used to create the table for the UTP Cable Length
Worksheet for Multiple Wiring Closets yield values equal to the
length of internal cabling within wiring closets (see Figure C-3) in
a multiple closet configuration. The term Internal Trunk
Length refers to trunk cabling length within the wiring closet,
adjusted to give consideration to ARL. The actual calculation
used in the table is described as follows:

Page C-10

CALCULATING RING LENGTH

Internal Trunk Length =

2 x (TCU Patch Cables) +

(Rack to Rack Patch Cables) +

(Concentrator to Concentrator Patch Cables)

where:

TCU Patch Cables = 12'

Rack to Rack Patch Cables =

45' x (number of Racks - 1)

Concentrator to Concentrator Patch Cables =

12' x (number of Concentrators - number of Racks)

STATION 1

WALL
PLATE

To Next

Wiring Closet

8'

MAIN
RING

OUT

8'

WIRING CLOSET

8'

30'

From Previous

Wiring Closet

IN

8'

STATION 2

WALL
PLATE

LOBE CABLING
TRUNK CABLING

Figure C-3. Wiring Closet Cabling

NOTE: You are hereby authorized to copy the next page (UTP Cable
Length Worksheet) in this appendix. Copy the worksheet for your
planning needs, but remember to keep a blank copy for future network
configuration changes.

Page C-11

CALCULATING RING LENGTH

UTP CABLE LENGTH WORKSHEET

Multiple Wiring Closets

1. Actual Longest UTP Lobe

4 Mbit/sec 16 Mbit/sec

1.

1.

ft.

ft.

2. UTP to Type 1 STP Conversion

(2.54 for 4 Mbit/s or 2.91 for 16 Mbit/s)

3. Equivalent Type 1 Lobe Length

(1) x (2) = (3)

4. Combined Trunk Length

(Sum of values for all closets, from Table below)

5. Internal Drive Distance

(3) + (4) = (5)

6. Maximum Drive Limit

(1263 feet for 4 Mbit/s or 569 feet for 16 Mbit/s)

6a. Internal Drive Distance

(from 5)

7. External Trunk Cable Budget

8. Actual External Trunk Cable Length

9. If you get a negative result, adjust
cable lengths or add active
components to the ring.

2.

3.

4.

5. ft.

6.

7.

9.

2.54

X

+ ft.

1263 ft.

–

–

3.

ft.

4.

5. ft.

6.

–

7.

ft.

ft.8.

9.

X2.

2.91

+ ft.

569 ft.

–

ft.8.

ft.

ft.

Internal Trunk Length for Multiple Wiring Closets

Number of Number of Racks (Multiple Closets)

Concentrators 12345 6 7 8910

1 24
2 36 69 Values are Type 1
3 48 81 114 Equivalent in Feet
4 60 93 126 159
5 72 105 138 171 204
6 84 117 150 183 216 249
7 96 129 162 195 228 261 294
8 108 141 174 207 240 273 306 339

9 120 153 186 219 252 285 318 351 384
10 132 165 198 231 264 297 330 363 396 429
11 144 177 210 243 276 309 342 375 408 441
12 156 189 222 255 288 321 354 387 420 453
13 201 234 267 300 333 366 399 432 465
14 213 246 279 312 345 378 411 444 477
15 225 258 291 324 357 390 423 456 489
16 237 270 303 336 369 402 435 468 501
17 249 282 315 348 381 414 447 480 513
18 261 294 327 360 393 426 459 492 525
19 273 306 339 372 405 438 471 504 537
20 285 318 351 384 417 450 483 516 549

Page C-12

CALCULATING RING LENGTH

C.4 CALCULATING MIXED CABLE TYPES

When calculating cable lengths for installations using mixed cable
types, you must compensate for different cable attenuations. Usually
cable lengths are most useful when converted to a Type 1 equivalent
length. Use the following formulas to convert to Type 1/2 from Type
6/9 and Type 1/2 from UTP at 4 Mbit/s or UTP at 16 Mbit/s:

Multiply the To find the
length of: By: length of:

Type 1 or Type 2 .39 UTP @ 4 Mbit/s

.34 UTP @ 16 Mbit/s
3/2 (1.5) Type 6 or Type 9

UTP 2.54 Type 1 or 2 @ 4 Mbit/s

2.91 Type 1 or 2 @ 16 Mbit/s

Page C-13