Token Ring Technology Report

142 Pages·1991·3.388 MB·English

by  Architecture Technology Corp. (Auth.)

TOKEN RING TECHNOLOGY
REPORT
THIRD EDITION
SEPTEMBER 1991
^ ARCHITECTURE DISTRIBUTED OUTSIDE THE USA/CANADA BY:
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CORPORATION 256 BANBURY ROAD
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^••1 SPECIALISTS IN COMPUTER ARCHITECTURE OXFORD OX27DH
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TECHNOLOGY
<£> Copyright 1991 Architecture Technology Corporation. All rights reserved. No part of this publication may be reproduced, photocopied, stored on a
retrieval system, or transmitted without the express prior written consent of the publisher.
TOKEN RING TECHNOLOGY
REPORT
THIRD EDITION
SEPTEMBER 1991
^ ARCHITECTURE DISTRIBUTED OUTSIDE THE USA/CANADA BY:
ELSEVIER ADVANCED TECHNOLOGY
^ • TECHNOLOGY
MAYFIELD HOUSE
CORPORATION 256 BANBURY ROAD
ELSEVIER
^••1 SPECIALISTS IN COMPUTER ARCHITECTURE OXFORD OX27DH
ADVANCED
P.O. BOX 24344 · MINNEAPOLIS, MINNESOTA 55424 · [phone] UNITED KINGDOM
TECHNOLOGY
<£> Copyright 1991 Architecture Technology Corporation. All rights reserved. No part of this publication may be reproduced, photocopied, stored on a
retrieval system, or transmitted without the express prior written consent of the publisher.
DISCLAIMER
Architecture Technology Corporation makes no representations or warranties with respect to the contents
hereof and specifically disclaims any implied warranties of merchantability of fitness for any particular purpose.
Further, reasonable care has been taken to ensure the accuracy of this report, but errors and omissions could
have occurred. Architecture Technology assumes no responsibility for any incidental or consequential damages
caused thereby.
Further, Architecture Technology Corporation reserves the right to revise this guide and to make changes from
time to time in the content thereof without obligation to notify any person or organization of such revision
or changes.
This disclaimer applies to all parts of this document.
FOREWORD
This report is an overview of the IBM Token-Ring technology and products built by IBM and compatible
vendors. It consists of three sections: (1) a summary of the design tradeoffs for the IBM Token-Ring, (2)
a summary of the products of the major compatible vendors, and (3) an appendix describing how the ring
operates and the protocol analyzer used to test the ring.
Readers wishing more detail on IBM ring products are referred to IBM Token-Ring Report and Reference
and IBM Token Ring Product Guide. Readers wishing to know more about rings and ring products in
general are referred to the The Ring-Based Local Networks Report. All of the above reports are
published by Architecture Technology Corporation.
Token-Ring Technology Report
Figure List
Section I
Figure 1: IEEE 802 Standards Summary 2
Figure 2: 802.2 Relationship To OSI Model 2
Figure 3: Token Passing 5
Figure 4: Manchester Encoding 9
Figure 5: Token-Ring Type 3 Wiring 10
Figure 6: Type 3 Wiring Components 11
Figure 7: MAU Configurations 14
Figure 8: IBM Token-Ring Network Multistation Access Unit 15
Figure 9: 16-Mbp Token-Ring Operation 22
Section II
Figure 1: IBM Token-Ring Network Connectivity 4
Figure 2: Token-Ring Interfaces 11
Figure 3: PC LAN Program Servers 15
Figure 4: Asynchronous Communication Server 16
Figure 5: 3270 Emulation Program 18
Figure 6: Series/1 Connect 20
Figure 7: OS/2 Communications Manager Interfaces 25
Figure 8: Type 3 Wiring Components 29
Figure 9: Cable Types 30
Figure 10: Performance Capabilities of Cable Types 31
Figure 11: MAU Configurations 33
Figure 12: MAU Rack Configuration with Repeater 34
Figure 13: Inside the MAU 35
Figure 14: MAU Wall Mounting 36
Figure 15: IBM Cabling System Evolution 36
Figure 16: Example ProNET-4 Configuration 48
Figure 17: Proteon Multistation Wire Centers 50
Figure 18: Racore Network Interface Cards 58
Figure 19: Comparison of PC Adapter Boards 63
Figure 20: Front, Rear Views of Type 3 MAU 63
Figure 21: Compatibility Summary 64
Figure 22: Supported Interfaces 65
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Token-Ring Technology Report
Figure 23: Network Management Bus, Connection Detail 72
Figure 24: Network Management Configuration, Local Site 73
Figure 25: Single MAU View Screen 74
Figure 26: AMRL Calculation Example 76
Figure 27: Redundant Main Ring Configuration 78
Figure 28: 818AT-6 As A Lobe Repeater 79
Figure 29: LattisNet System 3000 Token-Ring/Ethernet Configuration 82
Figure 30: ATS 1000 System Architecture 88
Figure 31: Token-Ring Network With MAUs 96
Figure 32: Intelligent-Type Token-Ring Adapter 105
Figure 33: The Relationship Between TRC and Network Manager 108
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Token-Ring Technology Report
1. Introduction
The IBM Token-Ring is a networking technology that was initially developed to provide local area
network capabilities for IBM Corporation. This technology and its implications take on the same level of
importance as the architecture of the Systems/360, IBM's SNA architecture, and the IBM Personal
Computer. This technology has the capability to provide long-term significant enhancements to IBM data
networking concepts. Because the impact of such a product set is more significant than just the total
announced product devices, this report will discuss in detail some of the technology trade-offs and issues
within the Token-Ring environment.
The Token-Ring was originally developed in the early 70's at the IBM labs in Zurich, Switzerland. The
transmission system (media and data included) was primarily decided upon based on trade-offs that were
made to try and achieve higher reliability in a LAN environment. The fundamental concept of the
network is that it follows the OSI structured protocols and provides for a long-term consistent growth path
with a protocol that gives fair and equal access to all stations at a given priority level within the ring. The
initial prototypes were demonstrated at Telecom '83 in Geneva, Switzerland. They were built using IBM
PCs, DisplayWriter, 6670 Laser Printer, and a Series 1 computer. These early rings had all the features of
the current rings and a majority of the fail-soft capabilities that are provided under the current structures.
The Cabling System was announced in March 1984, and the first Token-Ring network products were
announced in October 1985.
2. LAN Standards
One of the key issues within IBM is that of international standards for local area networks. There are a
number of reasons why standards are important to users. Some of the main reasons include the concepts
of: 1) greater compatibility of products; 2) higher product volumes (at a lower cost); 3) ease of attach-
ment to a particular network strategy; 4) allowing many different vendors to build multiple types of
connection strategies; 5) the ability for the user to choose equipment that best fits a particular need; and
6) the idea that the standards process allows fair and equal opportunity for all vendors (regardless of their
size) to impact the capabilities required in the standards.
The dominant standards group in the LAN area is IEEE 802 (see summary in Figure 1). Although other
groups are also working on LAN standards, the IEEE is the leading organization. In fact, the European
Computer Manufacturers Association (ECMA), Technical Committee 82 has followed the lead set by
IEEE 802. Within IEEE 802, the Computer Society sponsors the 802 project, where standards are drafted
and then go to the IEEE standards boards. IEEE submits its standards to the International Standards
Organization (ISO), where local area networks are the responsibility of Committee 97, Subcommittee 6,
for telecommunications and information exchange between systems. ISO standards are then provided to
the user community as published standards which provide functional specifications to which manufacturers
can build equipment.
Although a number of standards exist within IEEE 802, two are of primary interest to this report: IEEE
802.2 and IEEE 802.5. 802.2 describes a standardized logical link control (LLC) protocol. This LLC
protocol is actually a sublayer of Layer 2 (see Figure 2) of the OSI Reference Model (the Datalink Layer),
and defines the formats and protocols for exchanging frames between logical link control layers for two
devices attached to a local area network. It provides for two kinds of data transfer services: connection-
oriented and connectionless (datagram). A third type acknowledged connectionless is in draft status.
Connection-oriented service ensures that a given device can send an error-free, non-duplicated, properly
sequenced frame to another user. The connection-oriented protocol permits peer-to-peer communication
over the LAN as if the participating peers had a point-to-point link protocol between them. Actually,
multiple stations multiplex several logical data link protocols over a single physical link, the shared
I-l
Token-Ring Technology Report
1. Introduction
The IBM Token-Ring is a networking technology that was initially developed to provide local area
network capabilities for IBM Corporation. This technology and its implications take on the same level of
importance as the architecture of the Systems/360, IBM's SNA architecture, and the IBM Personal
Computer. This technology has the capability to provide long-term significant enhancements to IBM data
networking concepts. Because the impact of such a product set is more significant than just the total
announced product devices, this report will discuss in detail some of the technology trade-offs and issues
within the Token-Ring environment.
The Token-Ring was originally developed in the early 70's at the IBM labs in Zurich, Switzerland. The
transmission system (media and data included) was primarily decided upon based on trade-offs that were
made to try and achieve higher reliability in a LAN environment. The fundamental concept of the
network is that it follows the OSI structured protocols and provides for a long-term consistent growth path
with a protocol that gives fair and equal access to all stations at a given priority level within the ring. The
initial prototypes were demonstrated at Telecom '83 in Geneva, Switzerland. They were built using IBM
PCs, DisplayWriter, 6670 Laser Printer, and a Series 1 computer. These early rings had all the features of
the current rings and a majority of the fail-soft capabilities that are provided under the current structures.
The Cabling System was announced in March 1984, and the first Token-Ring network products were
announced in October 1985.
2. LAN Standards
One of the key issues within IBM is that of international standards for local area networks. There are a
number of reasons why standards are important to users. Some of the main reasons include the concepts
of: 1) greater compatibility of products; 2) higher product volumes (at a lower cost); 3) ease of attach-
ment to a particular network strategy; 4) allowing many different vendors to build multiple types of
connection strategies; 5) the ability for the user to choose equipment that best fits a particular need; and
6) the idea that the standards process allows fair and equal opportunity for all vendors (regardless of their
size) to impact the capabilities required in the standards.
The dominant standards group in the LAN area is IEEE 802 (see summary in Figure 1). Although other
groups are also working on LAN standards, the IEEE is the leading organization. In fact, the European
Computer Manufacturers Association (ECMA), Technical Committee 82 has followed the lead set by
IEEE 802. Within IEEE 802, the Computer Society sponsors the 802 project, where standards are drafted
and then go to the IEEE standards boards. IEEE submits its standards to the International Standards
Organization (ISO), where local area networks are the responsibility of Committee 97, Subcommittee 6,
for telecommunications and information exchange between systems. ISO standards are then provided to
the user community as published standards which provide functional specifications to which manufacturers
can build equipment.
Although a number of standards exist within IEEE 802, two are of primary interest to this report: IEEE
802.2 and IEEE 802.5. 802.2 describes a standardized logical link control (LLC) protocol. This LLC
protocol is actually a sublayer of Layer 2 (see Figure 2) of the OSI Reference Model (the Datalink Layer),
and defines the formats and protocols for exchanging frames between logical link control layers for two
devices attached to a local area network. It provides for two kinds of data transfer services: connection-
oriented and connectionless (datagram). A third type acknowledged connectionless is in draft status.
Connection-oriented service ensures that a given device can send an error-free, non-duplicated, properly
sequenced frame to another user. The connection-oriented protocol permits peer-to-peer communication
over the LAN as if the participating peers had a point-to-point link protocol between them. Actually,
multiple stations multiplex several logical data link protocols over a single physical link, the shared
I-l
Token-Ring Technology Report
PROTOCOLS LAYER OTHER
802.7
BROADBAND
802.1 INTERNETWORKING NETWORK ADVISORY
GROUP
oLDLr 802.2 LOGICAL LINK CONTROL LOLGINICKA L 802.8
C T FIBEROPTIC
EN
TE ADVISORY
II IS GROUP
SE S 802.3 802.4 802.5 802.6 MEDIA
* < MEDIA MEDIA MEDIA MEDIA ACCESS
ce 5 ACCESS ACCESS ACCESS ACCESS CONTROL
802.9
I INTEGRATED
LU
Ζ 802.3 802.4 802.5 802.6 VOICE/DATA
c\j CSMA/CD TOKEN TOKEN METRO. PHYSICAL
οω PASSING PASSING AREA LINK
BUS RING NETWORK
802.10
SECURITY
Figure 1: IEEE 802 Standards Summary
transmission medium of the Token-Ring. To accommodate multiple data link users at a single station
point, service access points (SAP) on the link protocol provide in-point addressing between the data link
user and the logical link control layer. In actuality, the logical link protocol of IEEE is independent of the
specific Token-Ring medium access control. Generally, IBM tends to favor the connection-oriented
services of the logical link protocol. In this environment, a data link connection is established between
two service access points prior to any exchange of information and may be reset or terminated at any time
by either data link user of the connection.
The connectionless service is a datagram type approach which frames are simply sent and received without
any correlation to previous or subsequent frames. Connectionless services are likely to require the use of
higher layer error control and sequencing services. All the frames exchanged between stations adhere to a
very simple format.
It contains the source and destination addresses, some control fields, and information fields. These
address fields identify the service access points of the source and the destination. The control field
specifies the type of frame, whether it is supervisory, unnumbered control information transfer, or
numbered information transfer. The procedures for connection-oriented service are much more complex
than the datagram-level service. There are a series of link protocols which allows the service access point
to send sequenced numbers so that end destination users may verify the proper ordering of frames in case
of re-transmission. Further, timers are associated with the services to ensure that acknowledgements are
received at appropriate times.
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Token-Ring Technology Report
LLC 802.2
Datalink
Layer
MAC
Physical
PHY 802.5
Layer
Medium
Figure 2: 802.2 Relationship To OSI Model
The medium access control (MAC) technique (of which 802.5 is one form) provides a control of media
access that is a sublayer of the Datalink protocol and allows that link layer to communicate to an
associated physical layer specification. The function of this layer is to ensure that individual stations are
properly assigned their opportunity to transmit over the LAN without interference from any other station
attempting to transmit at the same time. IEEE 802.5 defines the ring-oriented protocol. Access to the
link level is controlled by a token which is sequentially passed around the ring, and by changing the token
to a frame, a station gains access to the ring.
This report does not contain an in-depth discussion on token ring standards; IEEE documents contain
detailed discussions of these standards. These documents are available from the IEEE Computer Society
in Washington, D.C. When we discuss standardized approaches in the remainder of this report, we will be
referring to either IEEE 802.2 or IEEE 802.5.
3. Overview of Token Rings
The function of a token ring is to provide a means for nodes to be sequentially connected in a circular
topology and allow for the transmission of frames to the access control mechanism (token) to a frame and
allow for error detection and isolation. Because such networks can be physically limited in size (to areas
such as those typically found in offices or campuses), they may run at a very high rate. In data communi-
cations, however, the higher the rate of signal transmission, the more prone the signal is to errors.
Bearing this in mind, this section will describe general trade-offs of LAN development, as well as IBM's
LAN strategy. In the sections that follow, we will look at the protocols and technology of these networks
in detail.
The preferred LAN approach of IBM is a technology called a token ring. It is basically a network where
devices are sequentially connected together in a circular topology. Each device connects onto the network
n
through an interface called a ring interface adapter. This adapter handles all of the so-called basic
functions." That is, it knows how to recognize frames and addresses; it knows how to buffer data; it knows
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