ISO/IEC TR 11802-1:1995
(Main)Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Technical reports and guidelines — Part 1: The structure and coding of Logical Link Control addresses in Local Area Networks
Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Technical reports and guidelines — Part 1: The structure and coding of Logical Link Control addresses in Local Area Networks
Technologies de l'information — Télécommunications et échange d'information entre systèmes — Réseaux locaux et métropolitains — Rapports techniques et lignes directrices — Partie 1: Structure et codage des adresses de contrôle de liaison logique dans les réseaux locaux
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TECHNICAL
ISO/IEC
REPORT TR 11802-1
First edition
1995-02-01
Information technology -
Telecommunications and information
exchange between systems - Local and
metropolitan area networks - Technical
-
reports and guidelines
Part I:
The structure and coding of Logical Link
Control addresses in Local Area Networks
Technologies de l'informa tion - Télécommunications et échange
- Réseaux locaux et métropolitains -
d'information entre systèmes
Rapports techniques et lignes directrices -
Partie 1: Structure et codage des adresses de contrôle de liaison logique
dans les réseaux locaux
Reference number
ISO/IEC TR 11802-1 :I 995(E)
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ISO/IEC TR 11802-1:1995(E)
Contents Page
1 Scope 1
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
3
5 Unreserved addresses
4
6 Reserved addresses
7 Procedures for assignment of reserved addresses 4
4
7.1 General considerations
7.2 Specific procedures 4
8 LLC address assignments 6
Table 1 - Individual LLC address values 6
Table 2 - Group LLC address values 8
10
Annex A - General format of ISO/IEC 8802-2 addresses
Figure A.l - Format of the LLC address fields 10
11
Annex B - IEEE 802. - Sub Network Access Protocol (SNAP)
11
Figure B.l - Illustration of the IEEE 802 SNAP mechanism
Annex C - Guidelines for requesting an LLC address value 12
0 ISO/IEC 1995
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..
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O ISO/IEC ISOAEC TR 11802y995E)
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, but 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;
-type 3, when a technical committee has collected data of a different kind
from that which is normally published 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 11802-1, which is a Technical Report of type 3, was prepared by Joint
Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6,
Telecommunications and information exchange between systems.
This Technical Report cancels and replaces ISO/TR 11178:1991, of which it
constitutes a technical revision.
ISOlIEC 11802 consists of the following parts, under the general title Znformution
technology - Telecommunications and information exchange between systems -
Local and metropolitan area networks - Technical reports and guidelines:
- Part 1: The structure and coding of Logical Link Control addresses in Local
Area Networks [Technical Report]
- Part 2: Standard Croup MACAddresses [Technical Report]
...
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ISO/IEC TR 11802-1:1995(E) 0 ISO/IEC
Introduction
The standards for LANs generally comprise of the physical layer, the medium access control (MAC) sublayer, and the logical link
control (LLC) sublayer. In OS1 terminology, the MAC and LLC sublayers are considered to be sublayers of the OS1 data link
layer. Both the MAC and LLC sublayers contain fields for addressing.
This TR contains a description of the LLC addresses, together with a list of those 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
To this end this TR indicates the kind of considerations which
consume this resource in a considered and conservative manner.
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 TR will be kept up to date by ISO/IEC JTC 1 as new entries are added to the tables.
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TECHNICAL REPORT 0 ISO/IEC ISODEC TR 11802-1:1995(E)
Information technology - Telecommunications and
information exchange between systems - Local and
metropolitan area networks - Technical reports and
guidelines -
Part 1:
The structure and coding of Logical Link Contro addresses in
Local Area Networks
1 Scope
This Technical Report (TR) provides:
a description of the ISO/IEC 8802-2 addressing conventions,
a)
the consideration for the manner in which new LLC address uses are assigned an entry in this TR, and
b)
a record, in the form of a table, of assigned uses of ISOAEC 8802-2 address values.
c)
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 judgements regarding the entities which are identified by particular
address value@).
2 References
ISO/IEC TR 9577 : 1993, Information technology - Telecommunications and information exchange between systems - Protocol
identification in the network layer.
ISO/IEC 8802-2 : 1994, Information Technology - Telecommunications and information exchange between systems - Local and
metropolitan area networks - Specific requirements - Part 2: Logical link control.
1
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ISODEC TR 11802-1:1995(E) 0 ISO/IEC
3 Abbreviations
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 Neiwork Access Protocol
Source Service Access Point
SSAP
LSAP Link Service Access Point
4 General considerations
4.1 Functions of LLC addresses
Logical Link Control (LLC) protocol data units contain addressing information. This addressing information consists of two fields;
the Destination Service Access Point (DSAP) address field, and the Source Service Access Point (SSAP) address field. Each of
these is an 8 bit field and each is made up of two components.
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 IO', it denotes that the actual address is an individual address. When the address type
designation bit is set to Il', it denotes that the DSAP actual address is a group address. This Technical Report considers and
records the two types of actual address separately.
In the SSAP address field, the components are the commandresponse identifier bit, and seven bits of actual address. The actual
address in the SSAP field is always an individual address.
Table 1 is a record of individual address values and is applicable to SSAP actual addresses, and DSAP individual actual
addresses. Table 2 is a record of DSAP group actual addresses.
In the general case, an individual acîual address identifies a protocol, or set of protocols, in the next higher layer. In OS1
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 terns In italics, namely; address type designaiion bit, CommaWrespOnsa /dentifief bit and actualaddress are as defined in ISOAEC 8802-2. See ISOiIEC
8802-2 clause 3.3.1.1 items (2). (3). and (4).
2 The tomat of LLC addresses Is defined in ISO/iEC 8802-2. For infomation this is reproduced in Annex A.
3 An individual aciualaddressvalue does not necessarily have any reiatlonship with a group address of the same actutd addressvalue.
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 DSAPBSAP 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
commandresponse 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;
O111 1011
2111 1011
The following is the permitted binary representation of an example group actual address;
1101 O101
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 O 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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0 ISO/IEC
ISODEC TR 11802=1:1995(E)
D UDF
The following is 3 permitted hexadecimc 'epresentation c
the exam . group actual address shown in .2.1 (1101 0101);
AB
4.2.3 Bit order of transmission
The order of transmission of bits or other components of the octet address field by any particular MAC is outside the scope of this
Technical Report which describes LLC address values in terms of the significance of individual bits.
4.3 fhe null address
Function of the null address
4.3.1
The null LLC address designates the LLC entity associated with the underlying MAC 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 ISOAEC 8802-2.
4.3.2 Definition of the null address
The null address (DSAP and SSAP) is defined in ISOAEC 8802-2.
The null LLC address is included in table 1.
4.4 The global address
4.4.1 Function of the global address
The global LLC address is an address reserved from the range of group addresses (see table 2) and is used to identify all LSAPs
at the station identified by the MAC address.
4.4.2 Definition of the global address
The global LLC (DSAP) address is defined in ISOAEC 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 '1 11 11 11' 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 ISOiiEC TR 95ï7
The mechanisms described in ISOAEC 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 ISOAEC 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 ISOAEC 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 ISOAEC TR 9577.
In these cases, associating that protocol with a different actual address value could be necessary; see clause 7.
The address used in conjunction with SNAP
4.6
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.
5 Unreserved addresses
This Technical Report defines a range of individual actual addresses as unreserved. The corresponding DSAP and SSAP
'ZOO0 0001' through to 'Z011 11 11' inclusive (the left most bit is the least significant bit); see table 1.
addresses are in the range
3
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O ISO/IEC
ISO/IEC TR 11802-1:1995(E)
This Technical Report defines a range of group actual addresses as unreserved. The corresponding DSAP addresses are in the
range '1000 0000' through '101 1 11 11' inclusive (the left most bit is the least significant bit); see table 2.
Further definition of the unreserved addresses is beyond the scope of this Technical Report. They may be used for any purpose
whatsoever, including identification of protocols to which reserved addresses have been assigned. The responsibility for
controlling the use of unreserved LLC addresses rests with an appropriate authority, for example a system designer, an
im
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