Information technology — Protocol for providing the connectionless-mode network service: Provision of the underlying service by a subnetwork that provides the OSI data link service

Specifies the way in which the underlying service assumed by the protocol defined by ITU-T Rec. X.233 ISO/IEC 8473-1 is provided by a subnetwork that provides the OSI Data Link service defined by CCITT Rec. X.212 ISO/IEC 8886, through the operation of a Subnetwork Dependent Convergence Function (SNDCF) as described in ISO/IEC 8648. Also provides the PICS proforma for this protocol, in compliance with the relevant requirements and in accordance with the relevant guidance.

Technologies de l'information — Protocole de fourniture du service de réseau en mode sans connexion: Fourniture du service sous-jacent par un sous-réseau fournissant le service de liaison de données OSI

General Information

Status
Published
Publication Date
01-Mar-1995
Current Stage
9093 - International Standard confirmed
Completion Date
28-Jun-2001
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ISO/IEC 8473-4:1995 - Information technology -- Protocol for providing the connectionless-mode network service: Provision of the underlying service by a subnetwork that provides the OSI data link service
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INTERNATIONAL ISOJIEC
8473-4
STANDARD
First edition
1995-03-15
Information technology - Protocol for
providing the connectionless-mode
network service: Provision of the
underlying service by a subnetwork that
provides the OSI data link service
- Protocole de foumiture du service de
Technologies de /‘information
r&eau en mode sans connexion: Fourniture du service sous-jacent par un
sous-rbseau fournissant le service de liaison de don&es OS/
Reference number
ISO/l EC 8473-4: 1995(E)

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ISO/IEC 8473-4: 1995(E)
CONTENTS
Page
Scope . 1
Normative references 1
.....................................................................................................................................
2.1 Identical Recommendations I International Standards . 1
2.2 . 1
Paired Recommendations I International Standards identical in technical content
1
2.3 Additional references .
Definitions . 2
2
3.1 Reference model definitions .
3.2 Network layer architecture definitions . 2
2
3.3 Network layer addressing definitions .
3.4 Data link service definitions . 2
2
Abbreviations .
Subnetwork dependent convergence function . 3
5.1 General model . 3
5.2 Subnetwork user data . 3
5.3 Subnetwork dependent convergence functions used with subnetworks that provide the OS1 data
link service .
Annex A - PICS proforma .
.........................................................................................................................................
A. 1 Introduction
.....................................................................................................
A.2 Abbreviations and special symbols
A.3 Instructions for completing the PICS proforrna .
A.4 Identification .
A.5 Major capabilities .
A.6 Subnetwork dependent convergence functions for use with subnetworks that provide the OS1
9
connectionless Data Link service .
A.7 Subnetwork dependent convergence functions for use with subnetworks that provide the OS1
9
connection-mode Data Link service .
0 ISO/IEC 1995
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 the publisher.
ISO/IEC Copyright Office l Case postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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0 ISOLIEC ISO/IEC 8473-4: 1995(E)
Foreword
IS0 (the International Organization for Standardization) and IEC (the Inter-
national 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. 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 8473-4 was prepared by Joint Technical Com-
mittee ISO/IEC JTC 1, Information technology, Subcommittee SC 6, Telecom-
munications and information exchange between systems, in collaboration with
ITU-T. The identical text is published as ITU-T Recommendation X.623.
ISOIIEC 8473 consists of the following parts, under the general title Information
technology - Protocol for providing the connectionless-mode network service:
- Part 1: Protocol specification
- Part 2: Provision of the underlying service by an ISO/IEC 8802
subnetwork
- Part 3: Provision of the underlying service by an X.25 subnetwork
- Part 4: Provision of the underlying service by a subnetwork that
provides the OSI data link service
Annex A forms an integral part of this part of ISO/IEC 8473.
. . .
111

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ISO/IEC 8473-4: 1995(E)
0 ISO/IEC
Introduction
This is one of a set of Recommendations and International Standards produced to facilitate the interconnection of open
to achieve such interco nnection.
systems. The set covers the services and protocols required
This Recommendation I International Standard is positioned with respect to other related Recommendations and
International Standards by the layers defined in ITU-T Rec. X.200 1 ISOLIEC 7498-l. In particular, it defines the way in
which an X.25 subnetwork may be used within the Network layer to provide the abstract underlying service with respect
to which the protocol defined by ITU-T Rec. X.233 I ISO/IEC 8473-l is specified.
In order to evaluate the conformance of a particular implementation of this protocol, it is necessary to have a statement
of which of the protocol’s capabilities and options have been implemented. Such a statement is called a Protocol
Implementation Conformance Statement (PICS), as defined in CCITT Rec. X.290 I ISO/IEC 9646-l. A PICS proforma,
from which a PICS may be prepared for a specific implementation, is included in this Recommendation I International
Standard as normative Annex A.
iv

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ISO/IEC 8473-4 : 1995 (E)
INTERNATIONAL STANDARD
ITU-T RECOMMENDATION
INFORMATION TECHNOLOGY - PROTOCOL FOR PROVIDING THE
CONNECTIONLESS-MODE NETWORK SERVICE:
PROVISION OF THE UNDERLYING SERVICE BY A SUBNETWORK
THAT PROVIDES THE OS1 DATA LINK SERVICE
1
Scope
This Recommendation I International Standard specifies the way in which the underlying service assumed by the
protocol defined by ITU-T Rec. X.233 I ISO/IEC 8473-l is provided by a subnetwork that provides the OS1 Data Link
service defined by CCITT Rec. X.212 I ISO/IEC 8886, through the operation of a Subnetwork Dependent Convergence
Function (SNDCF) as described in ISO/IEC 8648.
This Recommendation I International Standard also provides the PICS proforma for this protocol, in compliance with the
relevant requirements, and in accordance with the relevant guidance, given in CCITT Rec. X.290 I ISO/IEC 9646-l.
2 Normative references
The following Recommendations and International Standards contain provisions which, through reference in this text,
constitute provisions of this Recommendation I International Standard. At the time of publication, the editions indicated
were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this
Recommendation I International Standard are encouraged to investigate the possibility of applying the most recent
editions of the Recommendations and Standards listed below. Members of IEC and IS0 maintain registers of currently
valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently
valid ITU-T Recommendations.
21 . Identical Recommendations I International Standards
-
ITU-T Recommendation X.200 (1994) I ISO/IEC 7498- 1: 1994, Information technology - @en Systems
Interconnection - Basic Reference Model.
-
CCITT Recommendation X.213 (1992) I ISO/IEC 8348: 1993, Information technology - Network service
definition for Open Systems Interconnection.
22 . Paired Recommendations I International Standards identical in technical content
-
CCITT Recommendation X.290 (1992), OH conformance testing methodology and framework for
protocol Recommendations for CCITT applications - General concepts.
ISO/IEC 9646- 1: 199 1, Information technology - Open Systems Interconnection - Conformance testing
methodology and framework - Part I: General concepts.
-
CCITT Recommendation X.212 (1988), Data link service definition for Open Systems Interconnection for
CCITT applications.
ISO/IEC 8886: 1992, Information technology - Telecommunications and information exchange between
systems - Data link service definition for Open Systems Interconnection.
23 . Additional references
-
ISO/IEC 8648: 1988, Information processing systems - Open Systems Interconnection - Internal
organization of the network layer.
ITU-T Rec. X.623 (1994 E)
1

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ISOKEC 8473-4 : 1995 (E)
3 Definitions
31 . Reference model definitions
This Recommendation I International Standard makes use of the following terms defined in ITU-T Rec. X.200 I
ISO/IEC 7498- 1:
network entity;
a)
b) Network layer;
c) Data link layer;
d) service;
service data unit;
e)
f) data link service;
protocol control information.
k9
32 . Network layer architecture definitions
This Recommendation I International Standard makes use of the following terms defined in ISO/IEC 8648:
subnetwork;
a>
b) subnetwork dependent convergence protocol;
subnetwork dependent convergence function;
C)
d) subnetwork access protocol.
Network layer addressing definitions
33 .
This Recommendation I International Standard makes use of the following term defined in CCITT Rec. X.213 I
ISO/IEC 8348:
-
subnetwork point of attachment.
Data link service definitions
34 .
This Recommendation I International Standard makes use of the following terms defined in CCITT X.212 I
ISO/IEC 8886:
a) data link service access point address;
b) data link connection.
4 Abbreviations
Connectionless-mode network protocol
CLNP
DL Data link layer
DLSDU Data link layer service data unit
PDU Protocol data unit
Quality of service
QOS
Service data unit
SDU
SN Subnetwork
SNDCF Subnetwork dependent convergence function
SNDCP Subnetwork dependent convergence protocol
SNICP Subnetwork independent convergence protocol
SNAcP Subnetwork access protocol
SNPA Subnetwork point of attachment
SNCR Subnetwork connection reference
SNSDU Subnetwork service data unit
2
ITU-T Rec. X.623 (1994 E)

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ISO/IEC 8473-4 : 1995 (E)
5 Subnetwork dependent convergence function
. General model
51
The general model for providing the underlying service assumed by the protocol in conjunction with a real subnetwork
that uses a connectionless subnetwork access protocol is as follows. The generation of an SN-UNITDATA Request by
the CLNP results in the generation of a corresponding subnetwork-specific UNITDATA request by the subnetwork
dependent convergence function. The receipt of a subnetwork-specific UNITDATA indication associated with delivery
of a connectionless data unit to its destination causes the SNDCF to generate an SN-UNITDATA Indication to the
CLNP.
The general model for providing the underlying service assumed by the CLNP in conjunction with a real subnetwork
that uses a connection-mode subnetwork access protocol is as follows. The generation of an SN-UNITDATA Request by
the CLNP causes a connection (logical channel, logical link, or the equivalent) to be made available for the transmission
of SN-User-data. If a connection cannot be made available, the SN-UNITDATA Request is discarded. The receipt of
subnetwork-specific PDUs containing SN-User-data causes the SNDCF to generate an SN-UNITDATA Indication to the
CLNP.
Where a real subnetwork is designed to use either a connectionless-mode or a connection-mode subnetwork access
protocol, the provision of the underlying service assumed by the CLNP is achieved by using the connectionless-mode
alternative.
52 . Subnetwork user data
The SN-Userdata is an ordered multiple of octets, and is transferred transparently between the specified subnetwork
points of attachment.
The underlying service assumed by the CLNP is required to support a service data unit size of at least 5 12 octets.
If the minimum service data unit sizes supported by all of the subnetworks involved in the transmission of a particular
PDU are known to be large enough that segmentation is not required, then either the full protocol or the non-segmenting
protocol subset may be used.
Data received from a subnetwork with protocol identification specifying this protocol (see ITU-T Rec. X.233 I
ISO/IEC 8473-l) shall be processed according to this Recommendation I International Standard.
NOTE - Data with other protocol identification should be ignored, since it may have been sent by an implementation
supporting additional protocols intended for use with this protocol.
53 . Subnetwork dependent convergence functions used with subnetworks that provide the OS1
data link service
This subclause defines a mapping of the OS1 Data Link service to the underlying service assumed by ITU-T Rec. X.233 I
ISO/IEC 8473-l. The OS1 Data Link service definition defines two types of Data Link service: a connectionless service
and a connection-mode service. SNDCFs are defined for subnetworks that provide either of these two modes of service.
5.3.1 SNDCF used with the connectionless Data Link service
The primitives defined for provision of the underlying service assumed by the CLNP map directly onto the UNITDATA
Request and Indication primitives defined for the connectionless Data Link service. Subnetwork dependent convergence
functions perform a mapping of the connectionless Data Link service onto the underlying service assumed by the CLNP.
The mapping is as follows. The generation of an SN-UNITDATA request by the CLNP results in the generation of a
DL-UNITDATA request (as described in CCITT Rec. X.212 I ISO/IEC 8886) by the subnetwork dependent
convergence function. A corresponding DL-UNITDATA indication prompts the SNDCF to generate an SN-
UNITDATA indication to the CLNP. No explicit subnetwork dependent convergence protocol control information is
exchanged between Network entities to provide this mapping of service.
The parameters of the SN-UNITDATA primitives are mapped onto the DL-UNITDATA primitives as follows. The
SN-Destination-Address and SN-Source-Address parameters are conveyed in the DL-Destination-Address and
DL-Source-Address parameters, respectively. The addresses used in the SN-UNITDATA request and indication
primitives are the Data Link service access point addresses described in CCITT Rec. X.212 I ISO/IEC 8886.
The SN-Quality-of-Service parameter is conveyed. The available QOS is known prior to the issuance of the
DL-UNITDATA request. There is no discrimination among DLSDUs.
parameter. The subnetwork must be able to support
The SN-Userdata parameter is conveyed in the DL-Userdata the
service data unit requirements defined in 5
.2.
ITU-T Rec. X.623 (1994 E) 3

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ISO/IEC 8473-4 : 1995 (E)
5.3.2 SNDCF used with the connection-mode Data Link service
The primitives defined for provision of the underlying service assumed by the CLNP are mapped onto the primitives
defined for the connection-mode Data Link service. Subnetwork dependent convergence functions perform a mapping of
the connection-mode Data Link service onto the underlying service assumed by the CLNP. The mapping is as follows.
On receiving an SN-UNITDATA request from the CLNP machine, the SNDCF determines if a Data Link connection
already exists between this source and destination address pair to convey the user data. If so, it issues a DL-DATA
request containing the SN-Userdata as the DL-Userdata.
If a Data Link connection does not already exist, a DL-CONNECT request is issued by the local/calling SNDCF with the
source and destination Data Link service access point addresses specified in the SN-UNITDATA request and waits for a
DL-CONNECT confirm. The SN-Quality-of-Service parameter is conveyed. The available QOS is known prior to the
issuance of the DL-CONNECT request. There is no requirement to use expedited data.
When the remote/called SNDCF receives a DL-CONNECT indication from the Data Link layer, it issues a
DL-CONNECT response. Once the corresponding DL-CONNECT confirm is received by the local/calling SNDCF, it
may issue a DL-DATA request(s) conveying user data. When the remote/called SNDCF receives a DL-DATA indication
from the Data Link l
...

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