ISO/IEC 13239:2000
(Main)Information technology — Telecommunications and information exchange between systems — High-level data link control (HDLC) procedures
Information technology — Telecommunications and information exchange between systems — High-level data link control (HDLC) procedures
Technologies de l'information — Télécommunications et échange d'information entre systèmes — Procédures de commande de liaison de données à haut niveau (HDLC)
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 13239
Second edition
2000-03-01
Information technology —
Telecommunications and information
exchange between systems — High-level
data link control (HDLC) procedures
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Procédures de commande de liaison de
données à haut niveau (HDLC)
Reference number
ISO/IEC 13239:2000(E)
©
ISO/IEC 2000
---------------------- Page: 1 ----------------------
ISO/IEC 13239:2000(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading
this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in
this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the
unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO/IEC 2000
All rights reserved. Unless otherwise specified, 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 either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 734 10 79
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
© ISO/IEC 2000 – All rights reserved
ii
---------------------- Page: 2 ----------------------
ISO/IEC 13239:2000(E)
Page
Contents
Foreword. v
Introduction. vi
1 Scope . 1
2 Normative references . 2
3 Definitions, acronyms and abbreviations . 3
3.1 Definitions . 3
3.2 Acronyms and abbreviations. 7
4 HDLC frame structure. 9
4.1 Frame formats . 9
4.2 Elements of the frame . 10
4.3 Transparency. 12
4.4 Transmission considerations. 14
4.5 Inter-frame time fill. 14
4.6 Invalid frame. 14
4.7 Extensions. 15
4.8 Addressing conventions. 15
4.9 Frame format field . 16
5 HDLC elements of procedures. 17
5.1 Data link channel states . 18
5.2 Modes . 18
5.3 Control field formats. 21
5.4 Control field parameters. 22
5.5 Commands and responses . 25
5.6 Exception condition reporting and recovery. 44
6 HDLC classes of procedures. 48
6.1 Types of data station . 48
6.2 Configurations . 49
6.3 Operational modes . 50
6.4 Addressing scheme . 50
6.5 Send and receive state variables.50
6.6 Fundamental classes of procedures. 50
6.7 Optional functions . 51
6.8 Consistency of classes of procedures . 51
6.9 Conformance to the HDLC classes of procedures. 51
6.10 Method of indicating classes and optional functions . 52
6.11 Unbalanced operation (point-to-point and multipoint) . 55
6.12 Balanced operation (point-to-point).58
6.13 Unbalanced connectionless operation (point-to-point and multipoint). 61
6.14 Balanced connectionless operation (point-to-point) . 63
6.15 Uses of the optional functions. 64
7 General purpose Exchange Identification (XID) frame. 71
7.1 General purpose XID frame information field structure . 71
7.2 General purpose XID frame information field encoding. 71
7.3 Single-frame exchange negotiation process . 75
7.4 Frame check sequence negotiation rules. 76
7.5 Rules for negotiation use of the frame format field in non-basic frame format mode. 76
8 Resolution/negotiation of data link layer address in switched environments. 77
8.1 Operational requirements. 77
8.2 Address resolution . 77
Annexes
A Explanatory notes on the implementation of the frame checking sequence . 79
B Example of the use of commands and responses . 81
C Time-out function considerations for NRM, ARM and ABM . 102
D Examples of typical HDLC procedural subsets. 104
E Illustrative examples of 16/32-bit FCS negotiation . 107
F Guidelines for communicating with LAPB X.25 DTEs. 109
G Examples of information field encoding in multi-selective reject frames . 110
H Frame format types . 111
© ISO/IEC 2000 – All rights reserved
iii
---------------------- Page: 3 ----------------------
ISO/IEC 13239:2000(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO 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. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft
International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights.
ISO and IEC shall not be held responsible for identifying any or all such patent rights.
International Standard ISO/IEC 13239 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 6, Telecommunications and information exchange between systems.
This second edition cancels and replaces the first edition (ISO/IEC 13239:1997), which has been technically revised.
Annex H forms a normative part of this International Standard. Annexes A to G are for information only.
© ISO/IEC 2000 – All rights reserved
iv
---------------------- Page: 4 ----------------------
ISO/IEC 13239:2000(E)
Introduction
This International Standard is a composition of the following HDLC-related International Standard
and approved Amendments:
� ISO/IEC 13239: 1997
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures
� ISOIEC 13239: 1997/DAM1
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures � Amendment 1: Non-basic frame formats �
General
� ISOIEC 13239: 1997/DAM2
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures � Amendment 2: Non-basic frame formats �
Provision for multiple address fields
� ISOIEC 13239: 1997/DAM3
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures� Amendment 3: Provision for 8-bit FCS
� ISOIEC 13239: 1997/DAM4
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures� Amendment 4: Frame format field
� ISOIEC 13239: 1997/DAM5
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures� Amendment 5: Intra-frame timeout
� ISOIEC 13239: 1997/DAM6
Information technology � Telecommunications and information exchange between systems �
High-level data link control (HDLC) procedures� Amendment 6: Header check sequence
High-level data link control (HDLC) procedures are designed to permit synchronous or start/stop,
code-transparent data transmission. The normal cycle of the code-transparent data communication
between two data stations consists of the transfer of frames containing information from the data
source to the data sink acknowledged by a frame in the opposite direction. Generally, until the data
station comprising the data source receives an acknowledgement, it holds the original information in
memory in case the need should arise for retransmissions.
In those situations that require it, data sequence integrity between the data source and the data sink is
effected by means of a numbering scheme, which is cyclic within a specified modulus and measured
in terms of frames. An independent numbering scheme is used for each data source/data sink
combination on the data link.
The acknowledgement function is accomplished by the data sink informing the data source of the
next expected sequence number. This can be done in a separate frame, not containing information,
or within the control field of a frame containing information.
HDLC procedures are applicable to unbalanced data links and to balanced data links.
© ISO/IEC 2000 – All rights reserved
v
---------------------- Page: 5 ----------------------
ISO/IEC 13239:2000(E)
Unbalanced data links
An unbalanced data link involves two or more participating data stations. For control purposes, one
data station on the data link assumes responsibility for the organization of data flow and for
unrecoverable data link level error conditions. The data station assuming these responsibilities is
known as the primary station in unbalanced connection-mode data links and as the control station in
unbalanced connectionless-mode data links, and the frames it transmits are referred to as command
frames. The other data stations on the data link are known as the secondary stations in unbalanced
connection-mode data links and as the tributary stations in unbalanced connectionless-mode data
links, and the frames they transmit are referred to as response frames.
For the transfer of data between the primary/control station and the secondary/tributary stations, two
cases of data link control are considered (see figures A and B). In the first case, the data station
comprising the data source performs a primary/control station data link control function and controls
the data station comprising the data sink that is associated with a secondary/tributary station data link
control function, by select-type commands.
In the second case, the data station comprising the data sink performs a primary/control station data
link control function and controls the data station comprising the data source that is associated with a
secondary/tributary station data link control function, by poll-type commands.
The information flows from the data source to the data sink, and the acknowledgements are always
transmitted in the opposite direction.
These two cases of data link control may be combined so that the data link becomes capable of two-
way alternate communication, or two-way simultaneous communication.
Select/information
Primary/
Secondary/
Control Tributary
station
station
Acknowledgement
Data source Data sink
Figure A���� Unbalanced data link functions (case 1)
Poll/acknowledgement
Primary/
Secondary/
Control
Tributary
station station
Information
Data sink Data source
Figure B���� Unbalanced data link functions (case 2)
Balanced data links
A balanced data link involves only two participating data stations. For control purposes, each data
station assumes responsibility for the organization of its data flow and for unrecoverable data link
level error conditions associated with the transmissions that it originates. Each data station is known
as a combined station in balanced connection-mode data links and as a peer station in balanced
connectionless-mode data links and is capable of transmitting and receiving both command and
response frames.
For the transfer of data between combined/peer stations, the data link control functions illustrated in
figure C are utilized. The data source in each combined/peer station controls the data sink in the
other combined/peer station by the use of select-type commands. The information flows from the
data source to the data sink, and the acknowledgements are always transmitted in the opposite
direction. The poll-type commands may be used by each combined/peer station to solicit
acknowledgements and status responses from the other combined/peer station.
© ISO/IEC 2000 – All rights reserved
vi
---------------------- Page: 6 ----------------------
ISO/IEC 13239:2000(E)
Select/information/acknowledgement/poll
Combined/ Combined/
Peer Peer
station station
Select/information/acknowledgement/poll
Data sink/data source Data sink/data source
Figure C���� Balanced data link functions
Data link configurations
HDLC classes of procedures describe methods of data link operation which permit synchronous or
start/stop, code-transparent data transmission between data stations in a variety of logical and
physical configurations. The classes are defined in a consistent manner within the framework of an
overall HDLC architecture. One of the purposes of this International Standard is to maintain
maximum compatibility between the basic types of procedures, unbalanced, balanced and
connectionless, as this is particularly desirable for data stations with configurable capability, which
may have the characteristics of a primary, secondary, combined, control, tributary, or peer station, as
required for a specific instance of communication.
Five fundamental classes of procedures (two unbalanced, one balanced, and two connectionless) are
defined herein. The unbalanced classes apply to both point-to-point and multipoint configurations
(as illustrated in figure D using the primary/secondary nomenclature) over either dedicated or
switched data transmission facilities. A characteristic of the unbalanced classes is the existence of a
single primary station at one end of the data link plus one or more secondary stations at the other
end(s) of the data link. The primary station alone is responsible for data link management, hence the
designation "unbalanced" classes of procedures.
Primary/
Control
station
Secondary/ Secondary/
Tributary Tributary
station station
A N
Figure D�� Unbalanced data link configuration
��
The unbalanced connectionless class applies to point-to-point configurations over either dedicated or
switched data transmission facilities, or to multipoint configurations over dedicated data transmission
facilities (as illustrated in figure D using the control/tributary nomenclature). A characteristic of the
unbalanced connectionless class is the existence of a single control station at one end of the data link
plus one or more tributary stations at the other end(s) of the data link. The control station is
responsible for determining when a tributary station is permitted to send. Neither the control station
nor the tributary station(s) support any form of connection establishment/termination procedures,
flow control procedures, data transfer acknowledgement procedures, or error recorvery procedures,
hence the designation “connectionless” class of procedures.
The balanced class applies to point-to-point configurations (as illustrated in figure E using the
combined nomenclature) over either dedicated or switched data transmission facilities. A
characteristic of the balanced class is the existence of two data stations, called combined stations, on
a logical data link, that may share equally in the responsibility for data link management, hence the
designation "balanced" class of procedures.
© ISO/IEC 2000 – All rights reserved
vii
---------------------- Page: 7 ----------------------
ISO/IEC 13239:2000(E)
I
Combined/ Combined/
Peer Peer
station station
A B
Figure E�� Balanced data link configuration
��
The balanced connectionless class applies to point-to-point configurations over either dedicated or
switched data transmission facilities (as illustrated in figure E using the peer nomenclature). A
characteristic of the balanced connectionless class is the existence of two data stations, called peer
stations, on a data link, that are each independently in control of when they can send. Neither peer
station supports any form of connection establishment/termination procedures, flow control
procedures, data transfer acknowledgement procedures, or error recovery procedures, hence the
designation "connectionless" class of procedures.
For each class of procedures, a method of operation is specified in terms of the capabilities of the
basic repertoire of commands and responses that are found in that class.
A variety of optional functions are also listed. Procedural descriptions for the use of the optional
functions are defined.
It is recognized that it is possible to construct symmetrical configurations for operation on a single
data circuit from the unbalanced classes of procedures which are defined in this International
Standard. For example, the combination of two unbalanced procedures (with I frame flow as
commands only) in opposite directions would create a symmetrical point-to-point configuration (as
illustrated in figure F).
Primary Secondary
station station
I
1 1
I
I
I
Secondary Primary
I
I
station station
2 2
Figure F���� Symmetrical data link configuration
These HDLC procedures define the exchange identification (XID) command/response frame as an
optional function for exchange of data link information (identification, parameters, functional
capability, etc.). The content and format for a general purpose XID frame information field is
defined.
These HDLC procedures also specify the parameters and procedures which may be employed by two
data stations to mutually determine the data link layer addresses to be used, prior to logical data link
establishment.
© ISO/IEC 2000 – All rights reserved
viii
---------------------- Page: 8 ----------------------
INTERNATIONAL STANDARD ISO/IEC 13239:2000(E)
Information technology — Telecommunications and information
exchange between systems — High-level data link control (HDLC)
procedures
1Scope
This International Standard specifies the frame structures, the elements of procedures, the classes of procedures, the content
and format of the general purpose Exchange Identification (XID) frame, and a means for resolution/negotiation of a data link
layer address in switched environments for data communication systems using bit-oriented high-level data link control
(HDLC) procedures.
NOTE� The use of the phrase “bit-oriented”, referring to the HDLC control procedures, pertains to the allocation of a non-integral number
of bits to various subfields used for HDLC control purposes. However, the frame as an entirety may be constructed from octet-oriented units
(e.g., start-stop mode) for transmission purposes.
The frame structure portion defines the relative positions of the various components of the basic frame format and the non-
basic frame format. The mechanisms used to achieve bit pattern independence (transparency), where and when required,
within the frame are also defined. In addition, three frame checking sequences (FCS) are specified; the rules for address field
extension are defined; and the addressing conventions available are described.
The elements of procedures portion specifies elements of data link control procedures for synchronous or start/stop, code-
transparent data transmission using independent frame numbering in both directions.
These HDLC elements of procedures are defined specifically in terms of the actions that occur on receipt of commands at a
secondary station, a tributary station, a peer station, or a combined station.
This International Standard is intended to cover a wide range of applications; for example one-way, two-way alternate or
two-way simultaneous data communication between data stations which are usually buffered, including operations on
different types of data circuits; for example multipoint/point-to-point, duplex/half-duplex, switched/non-switched,
synchronous/start-stop, etc.
The defined elements of procedures are to be considered as a common basis for establishing different types of data link
control procedures. This International Standard does not define any single system and should not be regarded as a
specification for a data communication system. Not all of the commands or responses are required for any particular system
implementation.
The classes of procedures portion describes the HDLC unbalanced classes of procedures, the HDLC balanced class of
procedures, and the HDLC connectionless classes of procedures for synchronous or start/stop data transmission.
For the unbalanced classes, the data link consists of a primary station plus one or more secondary stations and operates in
either the normal response mode or the asynchronous response mode in a point-to-point or multipoint configuration. For the
balanced class, the data link consists of two combined stations and operates in the asynchronous balanced mode in a point-to-
point configuration. For the unbalanced connectionless class, the data link consists of a control station plus one or more
tributary stations and operates in the unbalanced connectionless-mode in a point-to-point or multipoint configuration. For the
balanced connectionless class, the data link consists of two peer stations and operates in the balanced connectionless-mode in
a point-to-point configuration. In each class, a basic repertoire of commands and responses is defined, but the capability of
the data link may be modified by the use of optional functions.
Balanced operation is intended for use in circumstances which require equal control at either end of the data link.
Operational requirements are covered in accordance with the overall HDLC architecture.
The content and format of the Exchange Identification (XID) frame portion builds on the fact that the principal use of the
XID frame is to exchange data link information between two or more HDLC stations. For the purpose of this International
Standard, data link information shall include any and all essential operational characteristics such as identification,
authentication and/or selection of optional functions and facilities concerning each station. This International Standard
defines a single-exchange negotiation procedure for establishing operational characteristics when either one or more stations
are capable of providing multiple selections.
© ISO/IEC 2000 – All rights reserved
1
---------------------- Page: 9 ----------------------
ISO/IEC 13239:2000(E)
This International Standard provides a means for exchanging the necessary information to establish, at a minimum, a data
link connection between two correspondents wishing to communicate. It describes a general purpose XID frame information
field content and format for that purpose.
It defines encoding for information related to the basic HDLC standards only. Mechanisms are provided to permit the general
purpose XID frame information field to be used to negotiate private parameters in a single XID exchange simultaneously
with negotiation of the defined basic parameters.
This International Standard does not limit or restrict the use of the XID frame information field from defining other standard
formats for use in specific applications.
The following are examples of potential uses of the XID command/response frame interchange:
a) Identification of the calling and called stations when using circuit switched networks (including switched network
backup applications).
b) Identification of stations operating on non-switched networks requiring identification at start-up.
c) The XID command frame with an individual, group or all-station address may be used to solicit XID response
frame(s) from other station(s) on the data link, prior to or following data link establishment.
d) Negotiation of the Frame Check Sequence (FCS) to be used for subsequent information interchange, by stations that
support both 16-bit FCS and 32-bit FCS capabilities.
e) Convey higher layer information that may be required prior to data link establishment.
f) Transmission of an XID response frame at any respond opportunity to request an XID exchange to modify some of
the operational parameters (for example, window size) following data link establishment.
g) Negotiation of the number of protected bits in the frame when an Unnumbered Information with Header check (UIH)
frame is used.
The means for resolution/negotiation of a data link layer address in switched environments portion is applicable to data
stations employing HDLC balanced classes of procedures which provide the XID command/response capability with the two
specific parameter fields, identifi
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.