1、BRITISH STANDARD BS ISO/IEC 10177:1993 Implementation of ISO/IEC 10177:1993 Information technology Telecommunications and information exchange between systems Provision of the connection-mode Network internal layer service by intermediate systems using ISO/IEC8208, the X.25Packet Layer Protocol UDC
2、681.3:621.39BSISO/IEC10177:1993 This British Standard, having been prepared under the directionof the Information Systems Technology Standards Policy Committee, was publishedunder the authority ofthe Standards Board and comesintoeffect on 15October1993 BSI 02-2000 The following BSI references relate
3、 to the work on this standard: Committee reference IST/6 Draft for comment 90/67534 DC ISBN 0 580 22587 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Technical Comm
4、ittee IST/6, upon which the following bodies were represented: British Computer Society British Telecommunications plc CCTA (the Government Centre for Information Systems) Digital Equipment Co. Ltd. IBM United Kingdom Ltd. Information Systems Committee of the Universities Funding Council Institution
5、 of Electrical Engineers International Computers Limited Logica UK Ltd. Ministry of Defence Rank Xerox Ltd. Swift Project Consortium Amendments issued since publication Amd. No. Date CommentsBSISO/IEC10177:1993 BSI 02-2000 i Contents Page Committees responsible Inside front cover National foreword i
6、i Foreword iii Text of ISO/IEC 10177 1BSISO/IEC10177:1993 ii BSI 02-2000 National foreword This British Standard reproduces verbatim ISO/IEC 10177:1993 and implements it as the UK national standard. This British Standard is published under the direction of the Information Systems Technology Standard
7、s Policy Committee whose Technical Committee IST/6 has the responsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and European
8、developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Services, Publications, BSI, Linford Wood, Milton Keynes, MK14 6LE. A British Standard does not purport to include all the necessary provisions of a contra
9、ct. Users of 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, pages ii t
10、o iv, pages 1 to 28 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.ISO/IEC10177:1993 (E) ii BSI 02-2000 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Norma
11、tive references 2 3 Definitions 2 4 Abbreviations 3 5 Overview and principles of the protocol mapping 3 6 Conformance 4 7 General considerations in mapping Network connections 6 8 Protocol mapping for NC establishment and release 6 9 Protocol mapping for data transfer phase 13 10 SNDCP for use of Pe
12、rmanent Virtual Circuits 16 Annex A (normative) PICS Proforma 18 Annex B (normative) Modified PICS requirements for ISO/IEC 8208 23 Annex C (informative) Illustration of processing of Transit Delay QOS 26 Figure 1 Intermediate-system model 4 Figure C.1 Scenario and relaying model for transit delay c
13、alculation 27 Table 1 Static conformance requirements 5 Table 2 Protocol mapping for NILS NC establishment and release primitives and parameters 7 Table 3 Mapping between Cause/Diagnostic Code and Originator/Reason (Mapping independent of NC phase) 12 Table 4 Mapping from Cause/Diagnostic Code to Or
14、iginator/Reason (NC establishment phase) 12 Table 5 Mapping from Cause/Diagnostic Code to Originator/Reason (Data transfer phase) 13 Table 6 Protocol mapping for NILS primitives and parameters in NC data transfer phase 14 Table 7 Mapping between Cause/Diagnostic Code and Originator/Reason (NC reset)
15、 16ISO/IEC10177:1993 (E) BSI 02-2000 iii 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
16、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
17、 liaison with ISO and IEC, also take part in the work. 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
18、an International Standard requires approval by at least 75% of the national bodies casting a vote. International Standard ISO/IEC 10177 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Sub-Committee SC 6, Telecommunications and information exchange between systems. An
19、nex A and Annex B form an integral part of this International Standard. Annex C is for information only.iv blankISO/IEC10177:1993 (E) BSI 02-2000 1 Introduction This International Standard is one of the set of standards associated with the Network layer of ISO7498s Reference Model for Open Systems I
20、nterconnection (OSI), aimed collectively at provision and support of the OSI Network service defined in ISO8348. It has been developed within the general framework provided by ISO8648, Internal Organization of the Network Layer, andinaccordance with the more detailed modelofintermediate-system funct
21、ions defined in ISO/IEC10028. ISO/IEC 10028 defines the relaying functions of a Network-layer intermediate system, in terms of the Network internal layer service (NILS): the NILS models the information flow within the Network layer in support of instances of Network-layer communication, at a level o
22、f abstraction that is independent of particular protocols and subnetwork technologies. This International Standard specifies the mapping between the NILS and theX.25 packet layer protocol (specified in ISO/IEC8208) for those cases where a real interworking unit modelled by an abstract intermediate s
23、ystem operates theX.25 packet layer protocol at its point of attachment to a real subnetwork, in support of the OSI connection-mode Network service. The use of the X.25 packet layer protocol specified in this International Standard for interworking units is compatible with that specified in ISO 8878
24、:1987 for real end systems; indeed, in certain scenarios, the same packet exchanges between an interworking unit and an end system are described by ISO8878 when viewed from the end system, and by this International Standard when viewed from the interworking unit. This International Standard applies
25、to each environment in which ISO/IEC8208 is used in support of the connection-mode Network service, including among others: a Packet Switched Public Data Network a Packet Switched Private Data Network a Local Area Network use of switched access to a packet switched (public or private) data network,
26、eg, by ISDN, CSDN or PSTN other subnetworks where the DTE/DTE mode of the X.25 Packet Layer Protocol is used in support of the connection-mode Network service. 1 Scope This International Standard specifies the method by which a Network-layer interworking unit (IWU) uses the X.25 packet layer protoco
27、l specified in ISO/IEC 8208 to support the OSI connection-mode Network service. The specification is expressed in terms of a mapping between the Network internal layer service defined in ISO/IEC 10028 and the Virtual Call (VC) and Permanent Virtual Circuit (PVC) services of the X.25 packet layer pro
28、tocol. An IWU to which this International Standard applies interconnects, for any individual Network connection, two real subnetworks, at least one of which is accessed using the X.25 packet layer protocol. When both subnetworks are accessed using the X.25 packet layer protocol, the specification ap
29、plies independently to the IWUs operation on each subnetwork. In addition, this International Standard uses ISO/IEC 10028s definition of the relaying functions of an intermediate system to extend its application beyond a single subnetwork point of attachment, to specify the requirements to be met by
30、 an IWU as a whole in supporting the OSI connection-mode Network service. This International Standard covers operation of theX.25 packet layer protocol that is compatible with the 1984 and later versions of CCITTRecommendation X.25, and that is compatible with the 1980 version of X.25 when the Perma
31、nent Virtual Circuit service is used; compatibility with the 1980 version of X.25 for Virtual Calls is outside the scope of this International Standard. To enable use of the PVC service, this International Standard defines a set of subnetwork dependent convergence protocol (SNDCP) procedures. These
32、allow a given PVC to support one Network connection at a time, but to support different Network connections, with the same or different values for address and quality of service parameters, etc, at different times. The procedures also allow for the possibility of using a PVC in support of other prot
33、ocols, but not simultaneously with these procedures (apart from transient collision cases, which do not fail unnecessarily). To evaluate conformance of a particular implementation, it is necessary to have a statement of which capabilities and options have been implemented. Such a statement is called
34、 a Protocol Implementation Conformance Statement (PICS), as defined in ISO/IEC 9646-1. This International Standard provides the PICS proforma in compliancewith the relevant requirements, and in accordance with the relevant guidance, given in ISO/IEC 9646-2.ISO/IEC10177:1993 (E) 2 BSI 02-2000 This In
35、ternational Standard does not specify any requirements relating to the exchange of routing information or layer-management information between an IWU and other systems. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of t
36、his International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards listed
37、below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 7498:1984, Information processing systems Open Systems Interconnection Basic Reference Model. ISO/IEC 8208:1990, Information technology Data communications X.25 Packet Layer Protocol for Data Terminal Eq
38、uipment. ISO/IEC 8208:1990/Amd.3:1991, Information technology Data communications X.25 Packet Layer Protocol for Data Terminal Equipment, Amendment 3: Conformance requirements. ISO 8648:1988, Information processing systems Open Systems Interconnection Internal organization of the Network Layer. ISO/
39、IEC 9646-1:1991, Information technology Open Systems Interconnection Conformance testing methodology and framework Part1:General concepts. ISO/IEC 9646-2:1991, Information technology Open Systems Interconnection Conformance testing methodology and framework Part 2: Abstract test suite specification.
40、 ISO/IEC 10028:1993, Information technology Telecommunications and information exchange between systems Definition of the relaying functions of a Network layer intermediate system. CCITT Recommendation X.213 (1992)| ISO/IEC 8348:1993, Information technology Network service definition for Open System
41、s Interconnection. 3 Definitions 3.1 Reference model definitions This International Standard uses the following terms defined in ISO 7498: a) Network layer b) Network service c) Network connection 3.2 Network layer architecture definitions This International Standard uses the following terms defined
42、 in ISO 8648: a) real subnetwork b) interworking unit c) intermediate system d) subnetwork dependent convergence protocol 3.3 Network layer relaying definitions This International Standard uses the following terms defined in ISO/IEC 10028: a) Network internal layer service b) Network internal servic
43、e access point c) Network hop end point 3.4 Addressing definitions This International Standard uses the following terms defined in ISO/IEC8348: a) authority and format identifier b) domain specific part c) initial domain part d) initial domain identifier e) subnetwork point of attachment f) subnetwo
44、rk point of attachment address 3.5 X.25 packet layer protocol definitions This International Standard uses the following terms defined in ISO/IEC 8208: a) DTE/DXE interface b) logical channel c) M-bit sequence d) packet layer entity e) packet receive sequence number f) packet send sequence number g)
45、 Permanent Virtual Circuit h) Qualifier bit j) upper window edge k) Virtual Call l) windowISO/IEC10177:1993 (E) BSI 02-2000 3 4 Abbreviations 5 Overview and principles of the protocol mapping 5.1 Structure of the specification Clauses 7 to 9 define a mapping of the NILS primitives and parameters to
46、and from (a subset of) the packets, procedures and facilities of the X.25 PLP. That mapping applies to one side of an IWU e.g., item (4-A) in Figure 1. Clause 6 specifies the requirements on an IWU supporting the CONS over X.25 PLP, in terms of that mapping and of the full NILS definition in ISO/IEC
47、10028. Clause10 specifies the SNDCP procedures for use with PVCs. Annex A (normative) contains the PICS proforma, and Annex B (normative) lists the requirements applying to the related ISO/IEC 8208 PICS. NOTEApart from specification for the treatment of some mapping-protocol violations, in8.7 and9.1
48、.1, all the direct normative provisions of this International Standard are contained in clause6, and in clause10 for PVCs. However, the statements of those provisions in clause 6 rely upon, and can only be interpreted by reference to, the extended definitions in clauses7 to9 and in ISO/IEC 10028. 5.
49、2 NILS features to be supported The features of the Network internal layer servicefor connection-mode operation are (see ISO/IEC 10028, clause 6): a) NC establishment b) QOS negotiation c) normal data transfer d) flow control e) expedited data transfer f) receipt confirmation g) NC reset h) NC release j) connection control k) error diagnostics 5.3 General characteristics of the mapping between X.25 PLP and NILS The SNPA at which an IWU operates the X.25 PLP is identified with the DTE/DXE interface a
