1、BRITISH STANDARD BS ISO/IEC 8473-5:1997 Information technology Protocol for providing the connectionless-mode network service Part 5: Provision of the underlying service by ISDN circuit-switched B-channels ICS 33.080; 35.100.30BSISO/IEC8473-5:1997 This British Standard, having been prepared under th
2、e directionof the DISC Board, waspublished under the authorityof the Standards Boardand comes into effect on 15 December1997 BSI 08-1999 ISBN 0 580 28854 4 National foreword This British Standard reproduces verbatim ISO/IEC8473-5:1997 and implements it as the UK national standard. The UK participati
3、on in its preparation was entrusted to Technical Committee IST/6, Data communications, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK inte
4、rests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. From1 January1997, all IEC publications have the number60000 added to the old number. For instance
5、, IEC27-1 has been renumbered as IEC60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this d
6、ocument may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users o
7、f British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theISO/IEC title page, pagesii toiv, pages1
8、to12 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO/IEC8473-5:1997 BSI 08-1999 i Contents Page Nat
9、ional foreword Inside front cover Foreword iii Text of ISO/IEC8473-5 1ii blankBSISO/IEC8473-5:1997 ii BSI 08-1999 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Normative references 1 2.1 Identical Recommendations|International Standards 1 2.2 Paired Recommendations|International Standards id
10、entical intechnicalcontent 1 2.3 Additional references 2 3 Definitions 2 3.1 Reference model definitions 2 3.2 Network layer architecture definitions 2 3.3 Network layer addressing definitions 2 4 Abbreviations 2 5 Subnetwork dependent convergence function 3 5.1 General model 3 5.2 Subnetwork user d
11、ata 3 5.3 Subnetwork dependent convergence functions used with ISDNcircuit-switched B-channel 4 6 Conformance 7 6.1 Static conformance 7 6.2 Dynamic conformance 7 6.3 PICS proforma 7 Annex A PICS proforma 8 A.1 Introduction 8 A.2 Abbreviations and special symbols 8 A.3 Instructions for completing th
12、e PICS proforma 8 A.4 Identification 10 A.5 Subnetwork dependent convergence functions for use with X.25 subnetworks 11 Figure 1 ES-to-IS, IS-to-IS, or ES-to-ES directly connected via ISDN 4 Figure 2 Protocol layers at S- and T-reference points 4 Descriptors: Data processing, information interchange
13、, network interconnection, open system interconnection, network layer, data transmission, connectionless mode transmission, communication procedure, services, protocols.BSISO/IEC8473-5:1997 BSI 08-1999 iii Foreword ISO (the International Organization for Standardization) and IEC (theInternational El
14、ectrotechnical 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 tec
15、hnical 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. In the field of information technology, ISO and IEC have established a joint tech
16、nical committee, ISO/IEC JTC1. 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 least75% of the national bodies casting a vote. International Standard ISO/IEC8473-5 wa
17、s prepared by Joint Technical Committee ISO/IEC JTC1, Information technology, Subcommittee SC6, Telecommunications and information exchange between systems, in collaboration with ITU-T. The identical text is published as ITU-T Recommendation X.625. ISO/IEC8473 consists of the following parts, under
18、the general title Information technology Protocol for providing the connectionless-mode network service: Part 1: Protocol specification; Part 2: Provisions of the underlying service by an ISO/IEC8802 subnetwork; Part 3: Provision of the underlying service by an X.25 subnetwork; Part 4: Provision of
19、the underlying service by a subnetwork that provides the OSI data link service; Part 5: Provision of the underlying service by ISDN circuit-switched B-channels. Annex A forms an integral part of this part of ISO/IEC8473.iv blankBSISO/IEC8473-5:1997 BSI 08-1999 1 Introduction This Recommendation|Inte
20、rnational Standard is one of a set of Recommendations and International Standards produced to facilitate the interconnection of open systems. The set covers the services and protocols required to achieve such interconnection. This Recommendation|International Standard is positioned with respect to o
21、ther related Recommendations and International Standards by the layers defined in ITU-T Rec. X.200|ISO/IEC7498-1. In particular, it defines the way in which the B-channels of an ISDN subnetwork may be used within the Network layer to provide the abstract underlying service with respect to which the
22、protocol defined by ITU-T Rec. X.233|ISO/IEC8473-1 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 protocols capabilities and options have been implemented. Such a statement is called a Protocol I
23、mplementation Conformance Statement (PICS), as defined in CCITT Rec. X.290 and ISO/IEC9646-1. A PICS proforma, from which a PICS may be prepared for a specific implementation, is included in this Recommendation|International Standard as Annex A. 1 Scope This Recommendation|International Standard spe
24、cifies the way in which the underlying service assumed by the protocol defined by ITU-T Rec. X.233|ISO/IEC8473-1 is provided by a subnetwork that conforms to Recommendation Q.931 through the operation of a Subnetwork Dependent Convergence Function (SNDCF) as described in ISO/IEC8648. This Recommenda
25、tion|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 and ISO/IEC9646-1. 2 Normative references The following Recommendations and International Standards con
26、tain provisions which, through reference in this text, constitute provisions of this Recommendation|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
27、|International Standard are encouraged to investigate the possibility of applying the most recent edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. TheTelecommunication Standardization Bureau of the ITU ma
28、intains a list of currently valid ITU-T Recommendations. 2.1 Identical Recommendations|International Standards ITU-T Recommendation X.200 (1994)|ISO/IEC7498-1:1994, Information technology Open Systems Interconnection Basic Reference Model: The Basic Model. CCITT Recommendation X.213 (1992)|ISO/IEC83
29、48:1993, Information technology Open Systems Interconnection Network service definition. ITU-T Rec. X.233 (1993)|ISO/IEC8473-1:1994, Information technology Protocol for providing the connectionless-mode Network service: Protocol specification. ITU-T Rec. X.622 (1994)|ISO/IEC8473-3:1995, Information
30、technology Protocol for providing the connectionless-mode Network service: Provision of the underlying service by an X.25 subnetwork. ITU-T Rec. X.623 (1994)|ISO/IEC8473-4:1995, Information technology Protocol for providing the connectionless-mode Network service. Provision of the underlying service
31、 by a subnetwork that provides the OSI data link service. 2.2 Paired Recommendations|International Standards identical in technical content CCITT Recommendation X.290 (1992), OSI conformance testing methodology and framework for protocol Recommendations for CCITT applicationsGeneral concepts. ISO/IE
32、C9646-1:1994, Information technologyOpen Systems InterconnectionConformance testing methodology and frameworkPart1: General concepts.BSISO/IEC8473-5:1997 2 BSI 08-1999 2.3 Additional references CCITT RecommendationI.231 (1988), Circuit-mode bearer service categories. ITU-T RecommendationI.430 (1993)
33、, Basic user-network interfaceLayer1 specification. ITU-T RecommendationI.431 (1993), Primary rate user-network interface Layer1 specification. ITU-T Recommendation Q.921 (1993), ISDN user-network interfaceData link layer specification. ITU-T Recommendation Q.931 (1993), Digital Subscriber Signallin
34、g System No. 1 (DSS1)ISDN user-network interface layer3 specification for basic call control. ITU-T Recommendation X.25 (1993), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data network
35、s by dedicated circuit. CCITT Recommendation X.121 (1992), International numbering plan for public data networks. ISO/IEC7776:1995, Information technologyTelecommunications and information exchange between systemsHigh-level data link control proceduresDescription of the X.25 LAPB-compatible DTE data
36、 link procedures. ISO/IEC8208:1995, Information technologyData communicationsX.25 Packet Layer Protocol for Data Terminal Equipment. ISO8648:1988, Information processing systemsOpen Systems InterconnectionInternal organization of the Network Layer. ISO/IEC11575:1995, Information technologyTelecommun
37、ications and information exchange between systemsProtocol mappings for the OSI Data Link service. 3 Definitions 3.1 Reference model definitions This Recommendation|International Standard makes use of the following terms defined in ITU-T Rec. X.200|ISO/IEC7498-1: a) network entity; b) Network layer;
38、c) service; d) service data unit; e) protocol control information. 3.2 Network layer architecture definitions This Recommendation|International Standard makes use of the following terms defined in ISO/IEC8648: a) subnetwork; b) subnetwork dependent convergence protocol; c) subnetwork dependent conve
39、rgence function; d) subnetwork access protocol. 3.3 Network layer addressing definitions This Recommendation|International Standard makes use of the following term defined in CCITT Rec. X.213|ISO/IEC8348: subnetwork point of attachment. 4 Abbreviations For the purposes of this Recommendation|Interna
40、tional Standard, the following abbreviations apply: CLNP Connectionless-mode Network Protocol DCE Data Circuit-terminating Equipment DTE Data Terminal Equipment ES End System IS Intermediate SystemBSISO/IEC8473-5:1997 BSI 08-1999 3 5 Subnetwork dependent convergence function 5.1 General model The ge
41、neral 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-UNIT-DATA Request by the CLNP results in the generation of a corresponding subnetwork-specific U
42、NIT-DATA request by the subnetwork dependent convergence function. The receipt of a subnetwork-specific UNIT-DATA indication associated with delivery of a connectionless data unit to its destination causes the SNDCF to generate an SN-UNIT-DATA indication to the CLNP. The general model for providing
43、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-UNIT-DATA request by the CLNP causes a connection (logical channel, logical link, or the equivalent) to be made available for
44、 the transmission of SN-User-data. If a connection cannot be made available, the SN-UNIT-DATA Request is discarded. The receipt of subnetwork-specific PDUs containing SN-User-data causes the SNDCF to generate an SN-UNIT-DATA indication to the CLNP. Where a real subnetwork is designed to use either a
45、 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. 5.2 Subnetwork user data The SN-Userdata is an ordered multiple of octets, and is transferred transparently betw
46、een the specified subnetwork points of attachment. The underlying service assumed by the CLNP is required to support a service data unit size of at least512 octets. If the minimum service data unit sizes supported by all of the subnetworks involved in the transmission of a particular PDU are known t
47、o 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|ISO/IEC8473-1) shall be processed according to this Recomm
48、endation|International Standard. NOTEData 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. ISDN Integrated Services Digital Network PDU Protocol Data Unit PVG Permanent Virtual
49、Circuit QOS Quality of Service SDU Service Data Unit 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 TA Terminal Adapter TE Terminal EquipmentBSISO/IEC8473-5:1997 4 BSI 08-1999 5.3 Subnetwork dependent convergence functions used with ISDN ci
