1、BRITISH STANDARD BS ISO/IEC 10588:1993 Implementation of ISO/IEC10588:1993 Information technology Use of X.25 Packet Layer Protocol in conjunction with X.21/X.21 bis to providethe OSI connection-mode Network Service UDC 681.3:621.39BSISO/IEC 10588:1993 This British Standard, having been prepared und
2、er the directionof the Information Systems Technology Standards Policy Committee, was publishedunder the authorityofthe Standards Boardand comes into effect on 15August1993 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference IST/6 Draft for comment 91/67
3、840 DC ISBN 0 580 22449 X 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 Committee IST/6, upon which the following bodies were represented: British Computer
4、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 of Electrical Engineers International Computers Limited Logica UK Ltd. Ministry
5、of Defence Rank Xerox Ltd. Swift Project Consortium Amendments issued since publication Amd. No. Date CommentsBSISO/IEC 10588:1993 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword iii Text of ISO/IEC 10588 1BSISO/IEC 10588:1993 ii BSI 01-2000 Nation
6、al foreword This British Standard reproduces verbatim ISO/IEC10588:1993 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: ai
7、d 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 developments and promulgate them in the UK. NOTEInternational and European Stand
8、ards, as well as overseas standards, are available from Customer Services, Publications, BSI, Linford Wood, Milton Keynes, MK146LE. 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. Com
9、pliance 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, pagesi andii, theISO/IEC title page, pages ii to iv, pages1 to7 and a back cover. This standard has been updated (see copyright da
10、te) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO/IEC 10588:1993(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 underlying connections
11、4 7 Data link layer 5 8 Packet layer 6 Annex A X.30 Terminal Adaptors for ISDN 6 Annex B Bibliography 7 Figure 1 Configurations 3 Figure 2 Protocol stack 4 Table 1 Mapping of the X.21 call progress signals associated with clearing to the CONS Reasons 5 Descriptors: Data processing, telecommunication
12、s, information interchange, data transmission, network interconnection, open systems interconnection, network layer, network service, protocols.ISO/IEC 10588:1993(E) BSI 01-2000 iii Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commissi
13、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
14、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
15、C 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/IEC10588 was prepared by Joint Tech
16、nical Committee ISO/IEC JTC1, Information technology, in collaboration with the CCITT. The identical text is published as CCITT Recommendation X.613.iv blankISO/IEC 10588:1993(E) BSI 01-2000 1 1 Scope This CCITT Recommendation|International Standard is applicable to the environments where Recommenda
17、tion X.21 or X.21 bis is used and where the X.25 packet layer protocol (PLP), as standardized in ISO/IEC8208, is operated during the X.21/X.21 bis data phase to provide the OSI Connection-mode Network Service (CONS). These environments include a CSDN and an ISDN Terminal Adaptor complying with Recom
18、mendation X.30 which provides an X.21 access. The X.25 PLP operates either in the DTE/DTE or DTE/DCE mode. This provision is achieved by specifying the mapping of the CONS primitives and parameters to and from the elements of the protocols used (i.e.X.25 PLP and X.21). 2 Normative references The fol
19、lowing 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 Recommendations and Standards are subject to revi
20、sion 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 currently valid International Standards
21、. 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 technology Network service definition for Open Systems Interconnection 2.2 Paired Recommendat
22、ions|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 systems Open Systems Interconnection Basic Reference Model. CCITT Recommendation X.210 (1988),
23、 Open Systems Interconnection Layer Service Definition Conventions. ISO/TR 8509:1987, Information processing systems Open Systems Interconnection Service conventions. CCITT Recommendation X.223 (1988), Use of X.25 to provide the OSI Connection-Mode Network Service for CCITT applications. ISO 8878:19
24、87, Information processing systems Data Communications Use of X.25 to provide the OSI Connection-Mode Network Service. 2.3 Additional references CCITT Recommendation X.2 (1988), International data transmission services and optional user facilities in public data networks and ISDNs. CCITT Recommendat
25、ion X.21 (1992), Interface between data terminal equipment and data circuit-terminating equipment for synchronous operation on public data networks. CCITT Recommendation X.21 bis (1988), Use on public data networks of data terminal equipment (DTE) which is designed for interfacing to synchronous V-S
26、eries modems. 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.30 (1988), Support of X.21, X.21
27、bis and X.20 bis based data terminal equipments (DTEs) by an integrated services digital network (ISDN). CCITT Recommendation X.31 (1988), Support of packet mode terminal equipment by an ISDN. CCITT Recommendation X.32 (1988), Interface between data terminal equipment (DTE) and data circuit-terminat
28、ing 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. ISO 7776:1986, Information processing systems Data commu
29、nication High-level data link control procedures Description of the X.25 LAPB-compatible DTE data link procedures. ISO/IEC 8208:1990, Information technology Data communications X.25 Packet Layer Protocol for Data Terminal Equipment.ISO/IEC 10588:1993(E) 2 BSI 01-2000 3 Definitions For the purposes o
30、f 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|ISO7498: a) Network Connection; b) Network Layer; c) Network Service. 3.2 s
31、ervice conventions definitions this Recommendation|International Standard makes use of the following terms defined in CCITT Recommendation X.210|ISO/TR8509: a) Network Service provider; b) Network Service user. 3.3 network service definitions this Recommendation|International Standard makes use of t
32、he following terms defined in CCITT Recommendation X.213|ISO/IEC8348: 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 Recommendation X.25 and ISO/IEC8208: a) Data circuit-terminating e
33、quipment; b) Data terminal equipment; c) Registration packet; d) Virtual call. 3.5 X.21 definitions this Recommendation|International Standard makes use of the following term defined in CCITT Recommendation X.21: Call progress signal. 3.6 ISDN definitions this Recommendation|International Standard m
34、akes use of the following term defined in CCITT Recommendation X.31: Terminal adaptor. 4 Abbreviations 4.1 Reference model abbreviations 4.2 Network service abbreviations 4.3 X.25 abbreviations 4.4 ISDN abbreviations 4.5 Other abbreviations 5 Overview There are two basic configurations where the X.2
35、5 packet layer protocol (PLP), as standardized in ISO/IEC8208, may be operated over an X.21 connection to provide the OSI Connection-mode Network Service (CONS) defined in CCITT Rec.X.213|ISO/IEC8348. NL Network Layer NS Network Service OSI Open Systems Interconnection CONS Connection-mode Network S
36、ervice NSAP Network service access point QOS Quality of service SNPA Subnetwork 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 procedure balanced LIC Lowest
37、incoming channel LOC Lowest outgoing channel LTC Lowest two-way channel PLP Packet layer protocol ISDN Integrated services digital network IWF Interworking function TA Terminal adaptor TE Terminal equipment CSDN Circuit switched data network (public or private) PSDN Packet switched data network (pub
38、lic or private)ISO/IEC 10588:1993(E) BSI 01-2000 3 The first configuration is shown inFigure 1a) where two X.25 DTEs are directly connected by one or more concatenated CSDNs, or by one or more ISDNs and one or two X.30 TAs (seeAnnex B). In this case each DTE operates the DTE/DTE mode of ISO/IEC8208
39、(X.25 PLP) and ISO7776 (X.25 LAPB). The connection may be permanent or switched. The second configuration is shown inFigure 1b) where an X.25 DTE access a PSDN. In this case the DTE operates the DTE/DCE mode of ISO/IEC8208 (X.25 PLP) and ISO7776 (X.25 LAPB). When the connection is permanent this con
40、figuration is a regular X.25 scenario, while it relates to X.32 and X.31 when the connection is switched. CCITT Rec.X.223|ISO8878 specifies the method for providing the OSI Connection-mode Network Service (CONS) through the use of the X.25 PLP directly connected to another DTE or directly connected
41、to a packet switched data network. When a circuit switched (semi-permanent, hot line, or full circuit switched) 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|ISO8878 are necessary. These additi
42、onal provisions for a DTE connected to a CSDN, or to an ISDN via a TA, are specified by this Recommendation|International Standard. The applicable protocol stack is given inFigure 2. The X.25 PLP is used to convey all elements of all three phases of the OSI CONS. CCITT Rec.X.223|ISO8878 applies with
43、 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 establishment of a circuit switched connection) or in addition to t
44、hese mappings (e.g., to cover an unexpected disconnection of the circuit switched connection). At the physical layer (and for signalling for a circuit switched connection), either X.21 or X.21 bis may be used. At the data link layer ISO7776, as constrained by clause7 of this Recommendation|Internati
45、onal Standard, is used. At the network layer ISO/IEC8208, as constrained by clause8 of this Recommendation|International Standard, is used. The mapping of the elements of the CONS to the protocol and procedures of ISO/IEC8208 shall be as required by CCITT Rec.X.223|ISO8878. The remaining clauses of
46、this Recommendation|International Standard specify the provisions required in addition to these mappings. Figure 1 ConfigurationsISO/IEC 10588:1993(E) 4 BSI 01-2000 6 Control of underlying connections The following clauses cover the two types of underlying connections that can be operated: leased ci
47、rcuit connection, and circuit switched connection including direct call. 6.1 Leased circuit connection Both the X.21 and X.21 bis interfaces provide for a leased circuit connection. No additional procedures are required. 6.2 Circuit switched connection (including direct call) Both the X.21 and X.21
48、bis interfaces provide for a circuit switched connection. 6.2.1 Circuit switched connection originated by DTE The following additional procedure shall be used if a circuit switched connection is not already established or if an additional circuit switched connection is needed to support the addition
49、al traffic. The receipt by layer3 of an N-CONNECT request primitive shall first cause the X.21 or X.21 bis procedures to be used to establish the connection. Following the successful establishment of this connection and the X.21 or X.21 bis procedures for entering the data transfer phase at layer1, the ISO7776 and ISO/IEC8208 procedures shall apply as constrained by clauses7 and8 of this Recommendation|International Standard. Failure to establish the connection is indicated to the NS user by means of a N-DISCONN
