ISO/IEC 13239:1997
(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
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Standards Content (Sample)
ISOAEC
INTERNATIONAL
13239
STANDARD
First edition
1997-06-I 5
Information technology -
Telecommunications and information
exchange between systems - High-level
data link control (HDLC) procedures
TMcommunications et Bchange
Technologies de I’informa tion -
d ‘informa tion en tre sys t&mes - Pro&dures de commande de liaison de
don&es 2 haut niveau (HDLC)
Reference number
ISOAEC 13239: 1997(E)
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ISO/IEC 13239: 1997(E)
Contents
Page
iv
Foreword .
V
Introduction .
1
1 Scope .
2
............................................................................
2 Normative references
.............................................. 2
3 Definitions, acronyms and abbreviations
2
3.1 Definitions .
6
................................................................
3.2 Acronyms and abbreviations
.......................................................................... 8
4 HDLC frame structure
........................................................................... 8
4.1 Elements of the frame
10
4.2 Transparency .
12
Transmission considerations .
4.3
12
..............................................................................
4.4 Inter-frame time fill
........................................................................................ 13
4.5 Invalid frame
13
4.6 Extensions .
13
4.7 Addressing conventions .
14
HDLC elements of procedures .
5
........................................................................ 14
5.1 Data link channel states
14
5.2 Modes .
17
5.3 Control field formats .
5.4 Control field parameters . 19
..................................................................... 22
5.5 Commands and responses
......................................... 41
5.6 Exception condition reporting and recovery
................................................................. 45
6 HDLC classes of procedures
Types of data station . 45
6.1
...................................................................................... 46
6.2 Configurations
................................................................................ 46
6.3 Operational modes
6.4 Addressing scheme . 46
Send and receive state variables . 46
6.5
....................................................... 46
6.6 Fundamental classes of procedures
................................................................................ 47
6.7 Optional functions
.................................................... 48
6.8 Consistency of classes of procedures
6.9 Conformance to the HDLC classes of procedures . 49
Method of indicating classes and optional functions . 49
6.10
........................ 50
6.11 Unbalanced operation (point-to-point and multipoint).
......................................................
6.12 Balanced operation (point-to-point) 53
6.13 Unbalanced connectionless operation (point-to-point and multipoint). . 56
6.14 Balanced connectionless operation (point-to-point) . 58
............................................................... 60
6.15 Uses of the optional functions
0 ISO/IEC 1997
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ISO/IEC Copyright Office l Case postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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ISO/IEC 13239:1997(E)
OISO/IEC
7 General purpose Exchange Identification (XID) frame. . 65
General purpose XID frame information field structure. . 65
7.1
7.2 General purpose XID frame information field encoding. . 65
7.3 Single-frame exchange negotiation process . 69
7.4 Frame check sequence negotiation rules . 71
Resolution/negotiation of data link layer address in switched
8
71
environments .
8.1 Operational requirements . 71
8.2 Address resolution . 71
Annexes
A Explanatory notes on the implementation of the frame checking
sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
B Example of the. use of commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Time-out function considerations for NRM, ARM and ABM . . . . . . . . . . . . . . 96
C
D Examples of typical HDLC procedural subsets . . . . . . . . .*. 98
E Illustrative examples of FCS negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
F Guidelines for communicating with LAPB X.25 DTEs. . . . . . . . . . . . . . . . . . . . . . 103
Examples of information field encoding in multi-selective reject
G
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
frames 104
..o
111
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ISO/IEC 13239: 1997(E) 0 ISOAEC
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
organizations 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. 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.
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.
Annexes A to G of this International Standard are for information only.
iv
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ISO/IEC 13239: 1997(E)
OISOIIEC
Introduction
This International Standard i sa composition of the following HDLC-related International
Standards and Amendments:
0
ISOAEC 3309: 1993
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Frame
structure
0
ISO/IEC 3309: 1993/DAM4
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Frame
structure -Amendment 4: Optional range of FCS checking
0
ISO/IEC 4335:1993
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Elements
of procedures
0
ISO/IEC 4335:1993/Amd.6:1995
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Elements
of procedures - Amendment 6: Extension of HDLC sequence number modulus
beyond I28
0
ISO/IEC 4335:1993Mmd.7:1995
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Elements
of procedures - Amendment 7: Enhanced multi-selective reject option
0
ISO/IEC 4335: 1993fDAM8
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Elements
of procedures - Amendment 8: Unnumbered information frame with header
check (UIH) command and response
0
ISO/IEC 4335:1993/DAM9
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Elements
of procedures - Amendment 9: Span list encoding of the information field in the
multi-SREI frame
0
ISO/IEC 7809: 1993
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Classes of
procedures
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ISO/IEC 13239: 1997(E)
0 ISO/IEC
0
ISO/IEC 7809: 1993Amd. 10: 1995
Telecommunications and information exchange
Information technology ~
between systems - High-level data link control (HDLC) procedures - Classes
ofprocedures - Amendment 10: Extension of HDLC sequence number modulus
beyond I28
0
ISO/IEC 7809: 1993/DAM 11
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - Classes
of procedures - Amendment 1 I: Unnumbered information frame with header
check (UIH) command and response
0
ISO/IEC 7809: 1993/DAM 12
Information technology - Telecommunications and information exchange
High-level data link control (HDLC) procedures - Classes
between systems -
Amendment 12: Span list encoding of the information field in
of procedures -
the multi-SRUframe
ISO/IEC 8885: 1993
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - General
purpose XID frame information field content and format
ISO/IEC 8885: 1993/Amd.9:1995
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - General
purpose XID frame information field content and format - Amendment 9:
Extension of HDLC sequence number modulus beyond 128
0
ISO/IEC 8885:1993/DAMlO
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - General
purpose XID frame information field content and format - Amendment IO:
Unnumbered information frame with header check (UrH) command and response
0
ISO/IEC 8885:1993/DAMll
Information technology - Telecommunications and information exchange
between systems - High-level data link control (HDLC) procedures - General
purpose XID frame information field content and format - Amendment II:
Span list encoding of the information field in the multi-SREI frame
0
ISO/IEC 847 1: 1987
Information processing systems - Data communication - High-level data link
control balanced classes of procedures - Data-link layer address
resolution/negotiation in switched environments
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ISO/IEC 13239: 1997(E)
OISOIIEC
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.
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.
from the data source
The information flows to the data sink, and the acknowledgements
opposite
are always transmitted in the directi .on.
link control may be combined
These two cases of data so that the data link becomes
two-way altern .ate communication, or two-way simultan
capable of .eous communication.
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ISO/IEC 13239: 1997(E) 0 ISO/IEC
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.
4
Select/information
Primary/ b Secondary/
Control Tributary
station
1 station
Acknowledgement
. /
Data source Data sink
Figure A -Unbalanced data link functions (case 1)
Poll/acknowledgement
Primary/
b Secondary/
Control
Tributary
station 4
’ station
Information
Data sink Data source
Figure B -Unbalanced data link functions (case 2)
I Select/information/acknowledgement/poll .
Combined/ b Combined./
Peer Peer
station station
- Select/information/acknowledgementipoll -
_ _ ._ _ _ ._
Data sink/data source - Data sink/data source
Figure C - Balanced data link functions
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.
. . .
Vlll
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ISO/IEC 13239: 1997(E)
OISOIIEC
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/
I I4 b
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.
Combined/ Combined/
Peer Peer
I
station station
A B
Figure E - Balanced data link configuration
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.
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ISO/IEC 13239: 1997(E)
0 ISO/IEC
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
or error recovery procedures, hence the designation
acknowledgement procedures,
“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
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.
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ISO/IEC 13239: 1997(E)
INTERNATIONAL STANDARD OISO/IEC
Information technology - Telecommunications and
information exchange between systems - High-level data
link control (HDLC) procedures
1 Scope
This International Standard specifies the frame structure, 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 and the bit combination
for the frame delimiting sequence (flag). The mechanisms used to achieve bit pattern independence (transparency) within the
frame are also defined. In addition, two 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.
terms of action commands at a
These HDLC elements of procedures are defined specifically in the s that occur on receipt of
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.
in circumstances which require equ .a1 control at either end of the data link. Operational
Balanced operation is intended for use
requirements are covered in accordance with the overall HDLC architecture.
The content and format of the Exchange Identification (MD) 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
This International Standard defines a single-exchange
selection of optional functions and facilities concerning each station.
negotiation procedure for establishing operational characteristics when either one or more stations are capable of providing
multiple selections.
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.
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ISO/IEC 13239: 1997(E)
0 ISO/IEC
Mechanisms are provided to permit the general
It defines encoding for information related to the basic HDLC standards only.
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:
Identification of the calling and called stations when using circuit switched networks (including switched network backup
a)
applications).
Identification of stations operating on non-switched networks requiring identification at start-up.
b)
The XID command frame with an individual, group or all-station address may be used to solicit XID response frame(s)
C)
from other station(s) on the data link, prior to or following data link establishment.
Negotiation of the Frame Check Sequence (FCS) to be used for subsequent information interchange, by stations that
4
support both 16-bit FCS and 32-bit FCS capabilities.
Convey higher layer information that may be required prior to data link establishment.
e)
Transmission of an XID response frame at any respond opportunity to request an XID exchange to modify some of the
f)
operational parameters (for example, window size) following data link establishment.
Negotiation of the number of protected bits in the frame when an Unnumbered Information with Header check (UIH)
g)
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, identified below. It is used to select a pair of operational link addresses when preassigned, system designated
Additional XID frame functions (including the
addresses are not known on an a priori basis; e.g., switched circuited data links.
exchange of operational parameters, command/response support, higher layer information, etc.) may be accomplished in
conjunction with data link layer address determination or following address determination, with additional XID frame exchanges.
NOTE - Address re
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