1、I NTE R N AT1 0 NAL STANDARD ISOIIEC 8473-2 Fi rs t edit i o n 1996-03-1 5 Information technolgy - Protocol for providing the connectionless-mode network service - Part 2: Provision of the underlying service by an ISO/IEC 8802 subnetwork Technologies de /information - Protocole pour la fournittire d
2、ti service de reseau en mode sans connexion - Partie 2: Fourniture du service sous-jacent par un saus-reseau ISU/CEI 8802 National Standard of Canada CAN/CSA-ISO/IEC-8473-2-96 International Standard ISO/IEC 847321996 has been adopted, without modification, as CAN/CSA-ISO/IEC-8473-2-96, which has bee
3、n approved as a National Standard of Canada by the Standards Council of Canada. ISSN 03 17-5669 November 1996 Reference number ISO/IEC 8473-2:1996(E) ISO/IEC 8473-2: 1996(E) Con tents . Foreword 111 Introduction iv 4 5 Scope . -1 Normative references . 1 Definitions . 2 3.1 3.2 Network layer archite
4、cture definitions 2 3.3 Network layer addressing definitions 2 3.4 Local area network definitions 2 Reference model definitions 2 Abbreviations 2 Subnetwork dependent convergence function . 3 5.1 General model . 3 5.2 Subnetwork user data 3 5.3 Subnetwork dependent convergence functions used with IS
5、O/IEC 8802 subnetworks . 3 Annex A . PICS proforma 8 0 ISOIIEC 1994 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 f
6、rom the publisher . ISO/IEC Copyright Office Case postale 56 CH-1211 Genkve 20 Switzerland 11 0 ISO/IEC ISOAEC 8473-2:1996(E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardiz
7、ation. 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 mutu
8、al 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, ISOEC JTC 1. Draft International Standards adopted by the join
9、t 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 ISOLEC 8473-2 was prepared by Joint Technical Committee ISO/JEC JTC 1, lnfomzation technology,
10、 Subcommittee SC 6, Telecommunications and information exchange between systems. ISO/IEC 8473 consists of the following parts, under the general title Information technology - Protocol for providing the connectionless-mode network service: - Part I: Protocol specification - Part 2: Provision of the
11、underlying service by an ISO/IEC8802 subnetwork - Part 3: Provision of the underlying sewice by an X.25 subnetwork Part 4: Provision of the underlying service by a subnetwork that provides the USI data link service - Part 5: Provision of the underlying service for operation over ISDN circuit-switche
12、d B-channel Annex A forms an integral part of this part of ISO/IEC 8473. . 111 ISODEC 8473-2:1996(E) 0 ISOAEC Introduction This is one of a set of International Standards produced to facilitate the interconnection of open systems. The set covers the services and protocols required to achieve such in
13、terconnection. This International Standard is positioned with respect to other related International Standards by the layers defined in ISO/IEC 7498-1. In particular, it defines the way in which a local area network that conforms to ISO/IEC 8802 may be used as a subnetwork within the Network layer t
14、o provide the abstract underlying service with respect to which the protocol defined by ISODEC 8473- 1 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 capabilities and options have been i
15、mplemented. Such a statement is called a Protocol Implementation Conformance Statement (PICS), as defined in ISO/IEC 9646-1. A PlCS proforma, from which a PICS may be prepared for a specific implementation, is included in this International Standard as normative .Annex A. iv INTERNATIONAL STANDARD 0
16、 ISO/IEC ISO/IEC 8473-2: 1996(E) Information technology - Protocol for providing the connectionless-mode network service - Part 2: Provision of the underlying service by an ISO/IEC 8802 subnetwork 1 Scope This part of ISWIEC 8473 specifies the way in which the underlying service assumed by the proto
17、col defined by ISO/IEC 8473-1 is provided by a subnetwork that conforms to ISOAEC 8802 through the operation of a subnetwork dependent convergence function (SNDCF) as described in ISOAEC 8648. The SNDCF specified by this part of ISO/IEC 8473 may be used with any ISOAEC 8802 compliant subnetwork that
18、 provides the logical link control sublayer interface service defined by ISO/IEC 8802-2. This part of ISO/IEC 8473 also provides the PIGS proforma for this protocol, in compliance with the relevant requirements, and in accordance with the relevant guidance, given in ISO/IEC 9646- 1. 2 Normative refe
19、rences The following standards contain provisions which? through reference in this text, constitute provisions of this part of ISOiIEC 8473. At the time of publication, the editions indicated were valid. All International Standards are subject to revision, and parties to agreements based on this par
20、t of ISODEC 8473 are encouraged to investigate the possibility of applying the most recent editions of the Standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. ISOiIEC 7498- 1 : 1994, Information technology - Open Systems Interconnection - Bas
21、ic Reference Model: The Basic Model. ISO/IEC 8348: 1993, Information technology - Open Systems Interconnection - Network service definition. ISOAEC 8648: 1988 Information processing systems - Open Systems Interconnection - Internal organization of the network layer. ISO/IEC TR 8802- 1 : 1994. Inform
22、ation technologj - Telecommunications and information exchange between systems - Data communications - Local and metropolitan area nemorks - Specific requirements - Part i: Overview of Local Area Network Standards. IS O/IEC 8 802-2: 1994, lnformation technology - Telecommunications and information e
23、xchange between sysferns - Data communications - Local and metropolitan area networks - Spec$c requirements - Part 2: Logical link conrrol. ISO/IEC 9646- 1 : 199 1, information technology - Open Systems Interconnection - Conformance testing methodology and framework - Part 1: General concepts. 1 ISO
24、/IEC 8473-2: 1996(E) 0 ISOflEC 3 3.1 Definitions Reference model definitions This part of ISO/EC 8473 makes use of the following terms defined in ISO/IEC 7498-1: a) network entity b) Network layer c) service d) service data unit e) protocol control information 3.2 Network layer architecture definiti
25、ons This part of ISO/IEC 8473 makes use of the following terms defined in ISO/IEC 8648: a) subnetwork b) subnetwork dependent convergence protocol c) subnetwork dependent convergence function d) subnetwork access protocol 3.3 Network layer addressing definitions This part of ISOEC 8473 makes use of
26、the following terms defined in ISO/IEC 8348: a) subnetwork point of attachment 3.4 Local area network definitions This part of ISO/IEC 8473 makes use of the following terms defined in ISO/IEC 8802-1: a) local area network b) logical link control c) logical link control sublayer d) media access conrr
27、ol 4 CLNP LLC MAC PDU PlCS QoS SDU SN SNDCF SNPA Abbreviations connectionless-mode network protocol logical link control medium access control protocol data unit protocol implementation conformance statement quality of service service data unit subnetwork subnetwork dependent convergence function su
28、bnetwork point of attachment SNSDU subnetwork service data unit UI unnumbered information 2 0 ISOAEC ISOAEC 8473-2: 1996(E) 5 5.1 Subnetwork dependent convergence function General model The general model for providing the underlying service assumed by the protocol in conjunction with a real subnetwo
29、rk 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 UN ITD
30、ATA 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 su
31、bnetwork 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 discarde
32、d. The receipt of subnetwork-specific PDUs containing SN-User-data causes the SNDCF to generate an SN-UNITDATA Indication to the CLNP. Where a red subnetwork is designed to use either a connectionless-mode or a connection-mode subnetwork access protocol, the provision of the underlying service assum
33、ed by the CLN P is achieved by using the connectionless-mode alternative. 5.2 Subnetwork user data The SN-User-data consists of an ordered multiple of octets, and is transferred transparently between the specified subnetwork points of attachment. The underlying service assumed by the GLNP is require
34、d to support a service data unit size of at least 512 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-segmentin
35、g protocol subset may be used. Data received from a subnetwork with protocol identification specifying the CLNP protocol (ISO/IEC 8473) shall be processed according to ISODEC 8473- 1. NOTE - Data with other protocol idenrification should be ignored, since it may have been sent by an implementation s
36、upporting additional protocols intended for use with this protocol. 5.3 Subnetwork dependent convergence functions used with ISO/IEC 8802 subnetworks ESO/IEC 8802-2 describes two classes of logical link control (LLC). Class 1 provides an unacknowledged connectionless-mode service only. Class 2 provi
37、des both connectionless-mode and connection-mode services. For stations which conform to either of these two classes of service, the unacknowledged connectionless-mode service is used to provide the underlying service assumed by ISODEC 8473-1. The unacknowledged connectionless-mode service described
38、 in ISOfiEC 8802-2 is precisely that required by the CLNP. This service, with the exception of QoS, is summarized in Table 1. I Primitive Par am et e rs I D L- P ria r it y , Table 1 - ISO/IEC 8802-2 LLC sublayer service primitives 3 ISO/IEC 8473-2:1996(E) 0 ISO/IEC Subnetwork dependent convergence
39、functions perform a mapping of the unacknowledged connectionless-rnode service provided by a LLC Class 1 or Class 2 subnetwork onto the underlying service assumed by the CLNP. The mapping is as follows. The generation of an SN-UNITDATA request by the CLN P results in a DL-UN ITDATA request (as descr
40、ibed in ISO/IEC 8802-2) being generated by the subnetwork dependent convergence function. A corresponding D L- UNITDATA indication prompts the SNDCF to generate an SN-UNITDATA indication to the CLNP. No expIicit subnetwork dependent convergence protocol control information is exchanged between netwo
41、rk entities to provide this mapping of service. The addresses used in the SN-UNITDATA request and indication primitives are the seven-octet LAN station addresses described in ISO/IEC 8802-2, consisting of the six-octet medium access control (MAC) address plus the one-ocrer LLC service access point a
42、ddress. NOTE - In order to provide the underlying service assumed by ISO/IEC 8473-1, the underlying service shall be able to support a minimum service data unit size of 512 octets. While no SDU size resmction is imposed by ISOflEC 8802-2, the minimal requirement for a MAC is that it be capable of co
43、nveying unnumbered information (Ul) PDUs containing 128 octets in the information field. The additional constraint is therefore imposed on the SNDCF in such circumstances that it be able to convey at least 512 octets of user data iTI UI PDUs. 4 0 ISO/IEC ISOAEC 8473-2: 1996(E) Annex A1 (normative) P
44、lCS proforma A.1 Introduction The supplier of a protocol implementation which is claimed to conform to this part of ISO/IEC 8473 shall complete the following Protocol Implementation Conformance Statement (PICS) proforma. A completed PlCS proforma is the PlCS for the implementation in question. The P
45、lCS is a statement of which capabilities and options of the protocol have been implemented. The P1CS can have a number of uses, including use - by the protocol implementor, as a check-list to reduce the risk of failure to conform to the standard through oversight; - by the supplier and acquirer - or
46、 potential acquirer - of the implementation, as a detailed indication of the capabilities of the implementation, stated relative to lhe common basis for understanding provided by the standard PI CS proforma; - by the user - or potential user - of the implementation, as a basis for initially checking
47、 the possibility of interworking with another implementation (note that, while interworking can never be guaranteed, failure to interwork can often be predicted from incompatible PICSs); - by a protocol tester, as the basis for selecting appropriate tests against which to assess the claim for confor
48、mance of the implementation. A.2 Abbreviations and special symbols A.2.1 Status symbols M 0 O.a X : A mandatory optional optional, but support of at least one of the group of options labelled by the same numeral is required prohibited conditional-item symboI, including predicate identification (see
49、A.3.4) logical negation, appIied to a conditional items predicate A.2.2 Other symbols receive aspects of an item send aspects of an item 1 Copyright release for PI CS proformas Users of this part of ISO/lEC 8473 may freely reproduce the PlCS proforma in this Annex so that it can be used for its intended purpose and may further publish the completed PICS. 5 ISO/IEC 8473-2:1996(E) 0 ISO/IEC A.3 Instructions for completing the PlCS proforma A.3.1 General structure of the PICS proforma The first part of the PlCS proforma - Implementation Identification and Protocol Summary - is to be completed
