1、BRITISH STANDARD BS ISO/IEC 10732:1993 Implementation of ISO/IEC 10732:1993 Information technology Use of X.25 Packet Layer Protocol to provide the OSI connection-mode Network Service over the telephone network UDC 681.3:621.39BSISO/IEC10732:1993 This British Standard, having been prepared under the
2、 directionof the Information Systems Technology Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 August 1993 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference IST/6 Draft for comment 91/67
3、839 DC ISBN 0 580 224481 Committees responsible for this BritishStandard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Technical Committee IST/6, upon which the following bodies were represented: British Computer So
4、ciety 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 of Electrical Engineers International Computers Limited Logica UK Ltd. Ministry of
5、 Defence Rank Xerox Ltd. Swift Project Consortium Amendments issued since publication Amd. No. Date CommentsBSISO/IEC10732:1993 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword iii Text of ISO/IEC 10732 1BSISO/IEC10732:1993 ii BSI 01-2000 National f
6、oreword This British Standard reproduces verbatim ISO/IEC 10732:1993 and implements it as the UK national standard. This British Standard is published under the direction of the Information Systems Technology Standards Policy Committee whose Technical Committee IST/6 has the responsibility to: aid e
7、nquirers 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 developments and promulgate them in the UK. NOTEInternational and European Standard
8、s, 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 contract. Users of British Standards are responsible for their correct application. Compl
9、iance 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/IECtitlepage,pages ii to iv, pages1to 6, an inside back cover and abackcover. This standard has been updated
10、(see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO/IEC10732:1993(E) ii BSI 01-2000 Contents Page Foreword iii 1 Scope 1 2 Normative references 1 3 Definitions 2 4 Abbreviations 2 5 Overview 2 6 Control of underly
11、ing connections 4 7 Data link layer 5 8 Packet layer 5 Annex A Bibliography Inside back cover Figure 1 Configurations 3 Figure 2 protocol stack 3ISO/IEC10732:1993(E) BSI 01-2000 iii Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commissi
12、on) 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 technical activity. ISO an
13、d 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 technical committee, ISO/IE
14、C 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 10732 was prepared by Joint T
15、echnical Committee ISO/IEC JTC 1, Information technology, in collaboration with the CCITT. The identical text is published as CCITT Recommendation X.614.iv blankISO/IEC10732:1993(E) BSI 01-2000 1 1 Scope This CCITT Recommendation|International Standard is applicable to the environments where the X.2
16、5 packet layer protocol, as standardized in (PLP) ISO/IEC 8208, is operated over a telephone network connection to provide the OSI Connection-mode Network Service (CONS). These environments include a) telephone network leased circuit connection between two DTEs; b) telephone network switched connect
17、ion between two DTEs; c) DTE access to a PSDN via a telephone network leased circuit connection; and d) DTE access to a PSDN via a telephone network switched connection. This provision is achieved by specifying the mapping of the CONS primitives and parameters to and from the elements of the protoco
18、ls used. 2 Normative references The following CCITT Recommendations and International Standards contain 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 Recommenda
19、tions and Standards are subject to revision and parties to agreements based on this Recommendation|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
20、currently valid International Standards. The CCITT Secretariat maintains a list of the currently valid CCITT Recommendations. 2.1 Identical Recommendations|International Standards CCITT Recommendation X.213 (1992)|ISO/IEC 8348:1993, Information technologyNetwork service definition for Open Systems I
21、nterconnection. 2.2 Paired Recommendations|International Standards equivalent in technical content CCITT Recommendation X.200 (1988), Reference Model of Open Systems Interconnection for CCITT Applications. ISO 7498:1984, Information processing systemsOpen Systems InterconnectionBasic Reference Model
22、. CCITT Recommendation X.210 (1988), Open Systems Interconnection Layer Service Definition Conventions. ISO/TR 8509:1987, Information processing systemsOpen Systems Interconnection Service Conventions. CCITT Recommendation X.223 (1988), Use ofX. 25 to provide the OSI connection-mode network service
23、for CCITT applications. ISO 8878:1987, Information processing systemsData communicationsUse of X. 25 to provide the OSI Connection-Mode Network Service. 2.3 Additional references CCITT Recommendation V.25 (1988), Automatic answering equipment and/or parallel automatic calling equipment on the genera
24、l switched telephone network including procedures for disabling of echo control devices for both manually and automatically established calls. CCITT Recommendation V.25 bis (1988), Automatic calling and/or answering equipment on the general switched telephone network (GSTN) using the 100-Series inte
25、rchange circuits. CCITT Recommendation X.25 (1988), Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit. CCITT Recommendation X.32 (1988), Interface between
26、data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and accessing a packet switched public data network through a public switched telephone network or an integrated services digital network or a circuit switched public data network. I
27、SO 7776:1986, Information processing systemsData communicationHigh-level data link control proceduresDescription of the X. 25 LAPB-compatible DTE data link procedures. ISO/IEC 8208:1990, Information technology Data communicationsX. 25 Packet Layer Protocol for Data Terminal Equipment.ISO/IEC10732:19
28、93(E) 2 BSI 01-2000 3 Definitions For the purposes of this Recommendation|International Standard, the following definitions apply. 3.1 Reference model definitions This Recommendation|International Standard makes use of the following terms defined in CCITT Recommendation X.200|ISO 7498: a) Network Co
29、nnection; b) Network Layer; c) Network Service. 3.2 Service conventions definitions This Recommendation|International Standard makes use of the following terms defined in CCITT Recommendation X.210|ISO/T 8509: a) Network Service provider; b) Network Service user. 3.3 Network service definitions This
30、 Recommendation|International Standard makes use of the following terms defined in CCITT Recommendation X.213|ISO/IEC 8348: a) N-CONNECT request; b) N-DISCONNECT indication. 3.4 X.25 definitions This Recommendation|International Standard makes use of the following terms defined in CCITT Recommendati
31、on X.25 and ISO/IEC 8208: a) Data circuit-terminating equipment; b) Data terminal equipment; c) Registration packet; d) Virtual call. 4 Abbreviations 4.1 Reference model abbreviations 4.2 Network service abbreviations 4.3 X.25 abbreviations 4.4 Other abbreviations PSDN Packet switched data network (
32、public or private) 5 Overview There are two basic configurations where the X.25 packet layer protocol (PLP), as standardized in ISO/IEC 8208, may be operated over a telephone network connection to provide the OSI Connection-mode Network Service (CONS) defined in CCITT Rec. X.213|ISO/IEC 8348. The fi
33、rst configuration is shown in Figure 1a) where two X.25 DTEs are directly connected by a telephone network connection. In this case each DTE operates the DTE/DTE mode of ISO/IEC 8208 (X.25 PLP) and ISO 7776 (X.25 LAPB). The telephone network connection may be a leased circuit or switched. The second
34、 configuration is shown in Figure 1b) where an X.25 DTE accesses a PSDN. In this case the DTE operates the DTE/DCE mode of ISO/IEC 8208 (X.25 PLP) and ISO 7776 (X.25 LAPB). When the telephone network connection is a leased circuit this configuration is a regular X.25 scenario, while it relates to X.
35、32 when the telephone network connection is switched. CCITT Rec. X.223|ISO 8878 specifies the method for providing the OSI Connection-mode Network Service (CONS) through the use of the X.25 packet layer protocol (PLP). CCITT Rec. X.223|ISO 8878 covers the case of an X.25 DTE directly connected to an
36、other DTE or directly connected to a packet switched data network. When a switched telephone network connection is introduced into the path between the DTEs or between the DTE and a PSDN, a few provisions additional to those contained in CCITT Rec. X.223|ISO 8878 are necessary. These additional prov
37、isions for a DTE connected to the switched telephone network are specified by this Recommendation|International Standard. NL Network Layer NS Network Service OSI Open Systems Interconnection CONS Connection-mode Network Service NSAP Network Service access point QOS Quality of service SNPA Subnetwork
38、 point of attachment DCE Data circuit-terminating equipment DTE Data terminal equipment HIC Highest incoming channel HOC Highest outgoing channel HTC Highest two-way channel LAPB Link access procedurebalanced LIC Lowest incoming channel LOC Lowest outgoing channel LTC Lowest two-way channel PLP Pack
39、et layer protocolISO/IEC10732:1993(E) BSI 01-2000 3 Figure 1 Configurations NOTEThese procedures are not used in the leased circuit case. Figure 2 Protocol stackISO/IEC10732:1993(E) 4 BSI 01-2000 The applicable protocol stack is given in Figure 2. The X.25 PLP is used to convey all elements of all t
40、hree phases of the OSI CONS. CCITT Rec. X.223|ISO 8878 applies with regard to the mapping of the CONS primitives and parameters to the elements of the X.25 PLP. However, in certain cases discussed in the clauses below, additional provisions apply before these mappings can take place (e.g. to cover e
41、stablishment of a switched connection over the telephone network) or in addition to these mappings (e.g. to cover an unexpected disconnection of the switched connection). At the physical layer a V-series modem interface is used. Either Recommendation V.25 or V.25 bis may be used for signaling for a
42、switched connection over the telephone network. At the data link layer ISO 7776, as constrained by clause 7 of this Recommendation|International Standard, is used. At the network layer ISO/IEC 8208, as constrained by clause 8 of this Recommendation|International Standard, is used. The mapping of the
43、 elements of the CONS to the protocol and procedures of ISO/IEC 8208 shall be as required by CCITT Rec. X.223|ISO 8878. The remaining clauses of this Recommendation|International Standard specify the provisions required in addition to these mappings. 6 Control of underlying connections The following
44、 clauses cover the two types of underlying connections that can be operated: leased circuit connection and switched connection. 6.1 Leased circuit connection No additional procedures are required. 6.2 Switched connection 6.2.1 Switched connection originated by DTE The following additional procedures
45、 shall be used if a telephone network connection is not already established or if an additional telephone network connection is needed to support the additional traffic. The receipt by layer 3 of an N-CONNECT request primitive shall first cause the procedures to be used to establish the telephone ne
46、twork connection. Following the successful establishment of this connection and the modems have entered the data transfer phase, the ISO 7776 and ISO/IEC 8208 procedures shall apply as constrained by clauses 7 and 8 of this Recommendation|International Standard. Failure to establish the connection i
47、s indicated to the NS user by means of an N-DISCONNECT indication primitive with the originator parameter indicating “NS provider” and the reason parameter indicating “connection rejectionreason unspecifiedtransient”. 6.2.2 Switched connection originated toward DTE Once the telephone network connect
48、ion is established and the modems have entered the data transfer phase, the ISO 7776 and ISO/IEC 8208 procedures shall apply as constrained by clauses 7 and 8 of this Recommendation|International Standard. 6.2.3 Disconnection of the switched connection If one or more OSI Network Connections are esta
49、blished or in the process of being established on an established switched telephone network connection and this switched connection is disconnected or has failed (e.g. a failure occurred and a recovery might have been attempted but was not possible), then the provisions of ISO/IEC 8208 and CCITT Rec. X.223|ISO 8878 concerning the failure of layer 1 apply to the mapping to an N-DISCONNECT indication primitive for each OSI Network Connection established or in the process of being established. It is a local matter as to under what
