ISO/IEC TR 10178:1992
(Main)Information technology — Telecommunications and information exchange between systems — The structure and coding of Logical Link Control addresses in Local Area Networks
Information technology — Telecommunications and information exchange between systems — The structure and coding of Logical Link Control addresses in Local Area Networks
Provides: a) a description of the ISO 8802-2 addressing conventions; b) the consideration for the manner in which new LLC-address uses are assigned an entry in this Technical Report; c) a record, in the form of a table, of assigned uses of ISO 8802-2 address values.
Technologies de l'information — Télécommunications et échange d'information entre systèmes — Structure et codage des adresses de contrôle de liaison logique dans les réseaux locaux
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Standards Content (Sample)
TECHNICAL
REPORT
10178
First edition
1992-04-01
-
Information technology - Telecommunications
and information exchange between systems -
The structure and coding of Logical Link Control
addresses in Local Area Networks
Technologies de I’informa tion - T&kommunications et @change
d’information entre systemes - Structure et codage des adresses de
contrble de liaison logique dans les rheaux locaux
Reference number
~ -
___. - .I_.___________ -. -------- _-- _ __ _ _. _ _ iSO/IEC -T-R 10178:1992(E)
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ISOllEC TR 10178:1992(E)
Page
Contents
. . .
III
Foreword .
iv
Introduction .
1
1 .
S-P
1
2 References .
2
3 Abbreviations .
4 General considerations .
................................................................
4.1 Functions of LLC addresses
...............
4.2 Binary and hexadecimal representation of LLC addresses.
4.3 The null address .
4.4 .
The global address
4.5 The address used in conjunction with ISO/IEC TR 9577 .
4.6 The address used in conjunction with SNAP .
..................................................................................
5 Unreserved addresses
.....................................................................................
6 Reserved addresses
......................................
7 Procedures for assignment of reserved addresses
7.1 General considerations .
7.2 Specific procedures .
6
8 LLC address assignments .
6
Table 1 - Individual LLC address values .
............................................................ 8
Table 2 - Group LLC address values
Annexes
............................................ 10
A General format of IS0 8802-2 addresses
11
.............................
B IEEE 802 - Sub Network Access Protocol (SNAP)
12
C an LLC address value .
Guidelines for reouestina
6 lSO/lEC 1992
All rights reserved. No part of this publication may be reproduced or utilized in any form
or by any means,*electronic or mechanical, including photocopying and microfilm, without
permission in writing from the publisher.
ISO/lEC Copyright Office l Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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iSO/IEC TR 10178:1992(E)
Foreword
IS0 (the International Organization for Standardization) and IEC (the International
Electrotechnical Commission) form the specialized system for worldwide standardization.
National bodies that are members of IS0 or IEC participate in the development of International
Standards through technical committees established by the respective organization to deal
with particular fields of technical activity. IS0 and IEC technical committees collaborate in
fields of mutual interest. Other international organizations, governmental and non-
governmental, in liaison with IS0 and IEC, also take part in the work.
In the field of information technology, IS0 and IEC have established a joint technical
committee, ISO/IEC JTC 1.
The main task of technical committees is to prepare International Standards. In exceptional
circumstances a technical committee may propose the publication of a Technical Report of one
of the following types:
- type 1, when the required support cannot be obtained for the publication of an International
Standard, despite repeated efforts
- type 2, when the subject is still under technical development or where for any other reason
there is the future but not immediate possibility of an agreement on an International
Standard ;
technical committee has collected data of a different kind from that
- type 3, when a is
normally publis hed as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to
decide whether they can be transformed into International Standards. Technical reports
of type 3 do not necessarily have to be reviewed until the data they provide are considered to
be no longer valid or useful.
ISO/IEC TR 10178, which is a Technical Report of prepared by Joint Technical
type 3, was
Committee ISO/lEC JTC 1, lnforma tion technology.
Annexes A to C of this Technical Report are for information only.
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ISOllEC TR 10178:1992(E)
Introduction
The standards for lANs generally comprise the physical layer, the medium access control
(MAC) sublayer, and the logical link control (LLC) sublayer. In OSI terminology, the MAC and
LLC su blayers are considered to be su blayers of the OSI data link layer. Both the MAC and
LLC sublayers contain fields for addressing.
This Technical Report contains a description of the LLC addresses, together with a list of
values in current use.
The addressing space in LLC is limited, and it is such that it is considered to be a scarce
resource. It is therefore prudent to consume this resource in a considered and conservative
manner. To this end this Technical Report indicates the kind of considerations which will be
used by ISO/IEC when making the association between a particular LLC address value and
use to which it is put. These considerations are intended to be sufficiently broad to allow a wide
variety of LLC address uses to be recorded, and also sufficiently restrictive so that addresses
values are not unwisely assigned.
This Technical Report will be kept up to date by ISO/IEC JTC 1 as new entries are added to
the tables.
iv
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TECHNICAL REPORT ISO/IEC TR 10178:1992(E)
- Telecommunications and
Information technology
information exchange between systems - The structure and
coding of Logical Link Control addresses in Local Area
Networks
1 Scope
This Technical Report (TR) provides:
a description of the IS0 8802-2 addressing conventions,
a)
the consideration for the manner in which new LLC address uses are assigned an entry in this TR, and
W
a record, in the form of a table, of assigned uses of IS0 8802-2 address values.
Cl
This TR is for use by implementors to ascertain the value, or values, of LLC addresses that have been assigned for use in a
particular circumstance.
It is outside the scope of this TR to provide architectural judgments regarding the entities which are identified by particular address
value(s).
2 References
Telecommunications and information exchange between systems - Protocol
ISOAEC TR 9577 : 1990, Information technology -
identification in the network layer.
Local area networks - Part 2 : Logical Link Control.
IS0 8802-2:1988, information processing systems -
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ISO/IEC TR 10178:1992(E)
Abbreviations
3
The following abbreviations are used in this Technical Report.
DSAP Destination Service Access Point
IEEE Institute of Electrical and Electronics Engineers
LLC Logical Link Control
PDU Protocol Data Unit
SAP Service Access Point
SNAP Sub Network Access Protocol
SSAP Source Service Access Point
LSAP Link Service Access Point
4 General considerations
4.1 Functions of LLC addresses
In the DSAP address field, the components are an address type designation bit, and seven bits of actual address. When the
address type designation bit is set to ‘O’, it denotes that the actual address is an individual address. When the address type
designation bit is set to ‘l’, it denotes that the DSAP actual address is a group address. This Technical Report considers and
records the two types of actual address separately.
ents are the command/response identifier bit, and seven bits of actual address. The actual
In the SSAP address field, the compon
individual address.
address in the SSAP field is always an
applicable to SSAP actual addresses, and DSAP individual actual
Table 1 is a record of individual address values and is
actual addresses.
addresses. Table 2 is a record of DSAP group
In the general case, an individual actualaddress identifies a protocol, or set of protocols, in the next higher layer. In OSI
environments, the next higher layer is the Network Layer. In non-OS1 environments, the next higher layer is dependent on the
architecture in use.
There are certain exceptions to this general rule as discussed below.
NOTES
1 The terms ln italics, namely; address type deskptthn b#, wmman&response tientirier bit and actual address are as defined in IS0 8802-2. See IS0 8802-2
clause 3.3.1.1 items (2). (3), and (4).
2 The format of LLC addresses is defined in IS0 8802-2. For information this is reproduced in Annex A.
3 An individual actual address value does not necessarily have any relationship with a group address of the same actual address value.
4.2
Binary and Hexadecimal representation of LLC addresses
4.2.1 Binary representation
The seven-bit LLC actual address value is conveyed in the eight-bit DSAP/SSAP fields and therefore can be represented as a
sequence of eight binary digits. The least significant digit is shown to the left and the significance of the digits increases from left
to right. The least significant digit of the sequence represents the address type designation bit of the DSAP address field and the
command/response identifier bit of the SSAP address field, see figure A. 1.
The following are the two permitted binary representations of an example individual actual address;
0111 1011
2111 1011
The following is the permitted binary representation of an example group actual address;
11010101
4.2.2
Hexadecimal representation
The eight-bit binary representation of an actual address value may be represented as two hexadecimal digits encoding the value
of the octet address field with the least significant bit set to 0 in the case of an Individual address and the least significant bit set to
1 in the case of a group address.
2
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ISO/IEC TR 10178:1992(E)
The following is the permitted hexadecimal representation of the example individual actual address shown in clause 4.2.1 (Zl 11
1011);
DEIDF
The following is the permitted hexadecimal representation of the example group actual address shown in 4.2.1 (1101 0101);
A8
4.2.3
Bit order of transmission
of transmission of bits or other components of the octet address field by any particular MAC is outside the
The order of this
Technical Report which describes LLC address values in ter .ms of the sign ificance of individual bits.
. 4.3 The null address
4.3.1 Function of the null address
The null LLC address designates the LLC entity associated with the underlying SAP. The null address does not identify any
higher layer protocol nor the LLC sublayer management entity.
The null address is only valid for use in the address fields of XID and TEST PDUs. The use of the null address (DSAP and SSAP)
is specified in IS0 8802-2.
4.3.2 Definition of the null address
The null address (DSAP and SSAP) is defined in IS0 8802-2.
The null LLC address is included in table 1.
4.4 The global address
4.4.1 Function of the global address
address reserved from the range of addresses (see table 2) and is
The global LLC address is an to identify all LSAPs
group
at the station identified by the MAC address.
4.4.2
Definition of the global address
The global LLC (DSAP) address is defined in IS0 8802-2.
The global LLC address is included in table 2.
NOTE - The global address can only exist as a DSAP address. The Individual actual addresses value ‘111 1111' in DSAP and SSAP address fields is a different
address and should not be confused with the global address.
4.5 The address used in conjunction with ISOAEC TR 9577
The mechanisms described in ISO/IEC TR 9577 is an important feature of this Technical Report. It provides a means for
standardised network layer protocols to be self identifying. Protocols within the scope of ISO/IEC TR 9577 do not therefore need
to be separately identified by means of distinct individual actual address values. A specific individual actual address has been
assigned to ISO/IEC TR 9577 and this is recorded in table 1.
The considerations in clause 7 include the notion that whenever possible, new protocols should be identified by ISO/IEC TR 9577.
It might not be possible in all cases to identify the protocol which operates above the LLC sublayer by means of ISO/IEC TR 9577.
fferent actual address value could be necessary; see clause 7.
In these cases, associatin g that protocol with a di
4.6 The address used in conjunction with SNAP
Proprietary protocols do not qualify for inclusion in this Technical Report, nor are they suitable for identification by ISO/IEC TR
9577. To accommodate the use of private and proprietary protocols in a LAN environment, the method defined in Annex B is
available.
This method of identifying private/proprietary protocols is associated with a specific individual actual address value as indicated in
table 1.
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ISO/IEC TR 10178:1992(E)
5 Unreserved addresses
addresses as unreserved.
This Technical Report defines a range of individual actual The corresponding DSAP and SSAP
1 11’ inclusive (the left most bit is the least significant bit); see table
addresses are in the range ‘2000 0001 ‘ through to ‘ZOll 1 1.
This Technical Report defines a range of group actual addresses as unreserved. The corresponding DSAP addresses are in the
range ‘1000 0000’ through ‘1011 1111’ inclusive (the left most bit is the least significant bit); see table 2.
Further definition of the unreserved addres
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