1、INTERNATIONAL ISO/IEC STANDARD 9574 Second edition 1992-12-15 Information technology - Provision of the OSI connection-mode network service by packet mode terminal equipment to an integrated services digital network (ISDN) Technologies de Iinformation - Fourniture du service de rkseau 0.9 en mode co
2、nnexion par un terminal en mode paquet raecord and b) a packet mode ISDN terminal (El) operating ISO/IEC 8208 packet layer protocol (PLP) and connected to an ISDN at either the S or T reference point. This Recommendation 1 International Standard is applicable: a when operating according to Recommend
3、ation X.3 1, either a TEl or a TE2 is connected to a packet handler in an ISDN or an access unit to a packet-switched data network via an ISDN; b) when using an ISDN circuit-switched channel, either TEls and/or TE2EAs are connected directly to each other (i.e. the terminals operate in DTl3/DTl3 mode
4、). This Recommendation 1 International Standard does not address TE2s using TAs (at the R reference point) when using an ISDN circuit-switched channel with the terminals operating in DTE/DTE mode (see Recommenda- tion X.6 13 I ISO/IEC 10588). NOTES 1 The definitions of TEI, TE2 and TA equipment, and
5、 R, S, and T reference points are given in Recommenda- tion I.41 1. 2 This Recommendation 1 International Standard applies to a TBl or TE2/TA (i.e. an OS1 End System) regardless of whether it is a physically separate system or embedded in other equipment such as a PBX. This Recommendation 1 Internat
6、ional Standard addresses the provision of the CONS using Virtual Calls as described in Recommendation X.25. It does not address the use of X.25 Permanent Virtual Circuits. The extension of this Recommendation 1 International Standard to include the use of X.25 PVCs is for further study. NOTE -This R
7、ecommendation 1 International Standard uses numbers to identify layers, rather than their names. This is done to align the terminology of this document with the terminology of the related ISDN Recommendations, and does not imply any change in the functionality of the layers from that defined in the
8、reference model of open systems interconnectiou. CCIIT Rec. X.612 (1992 E) 1 ISO/IEC 9574 : 1992 (E) 2 Normative references The following CCITT Recommendations and ISOLEC International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation 1
9、International Standard. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject to revision. Parties to agreements based on this Recommendation 1 International Standard are encouraged to investigate the possibility of applying the most recent edit
10、ions-of the Recommendations and Standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. The CCIIT Secretariat maintains a list of currently valid CCIIT Recommendations. 2.1 Identical Recommendations I International Standards - CCITT Recommendatio
11、n X.213 (1992) I ISO/lEC 8348: 1992, Information technology - Network service definition for Open Systems Interconnection 2.2 Paired Recommendations 1 International Standards equivalent in technical content - CCITT Recommendation X.200 (1988), Reference model of open systems interconnection for CCIT
12、T applications. IS0 7498:1984, Information processing systems - Open Systems Interconnection - Basic Reference Model. - CCIlT Recommendation X.210 (1988), Open systems interconnection layer service definition conventions. ISOER 8509:1987, Information processing systems - Open Systems Interconnection
13、 - Service conventions. - CCITf Recommendation X.223 (1988), Use of X.25 to provide the OS1 connection-mode network service for CCITT applications. IS0 8878:1987, Information processing systems - Data communications - Use of X.25 to provide the OS1 connection-mode network service. 2.3 Additional ref
14、erences - CCITI Recommendation I.23 1 (1988), Circuit-mode bearer service categories. - CCITf Recommendation I.232 (1988), Packet-mode bearer service categories. - CCIIT Recommendation 1.430 (1988), Basic User-Network Interface Layer I Specification. - CCITT Recommendation I.43 1 (1988), Primary Rat
15、e User-Network Interface Luyer I Specification. - CCITI Recommendation Q.921 (1.441) (1988), ISDN User-Network Interface Data Link Layer Specification. - CCITI Recommendation Q.93 1 (I.45 1) (1988), ISDN User-Network Interface Luyer 3 Specifcution for Basic Call Control. - CCITT Recommendation V.25
16、bis (1988), Automatic Answering Equipment and/or Parallel Automatic Calling Equipment on the General Switched Telephone Network Including Procedures for Disabling of Echo Control Devices for Both Manually and Automatically Established Calls. - CCIIT Recommendation X.21 (1988), Interface Between Data
17、 Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for Synchronous Operation on Public Data Networks. - CCIIT Recommendation x.21 bis (1988), Use on Public Data Networks of Data Terminal Equipment (DTE) which is Designed for Interfacing to Synchronous V-series Modems. 2 CCITT Rec
18、. X.612 (1992 E) ISO/IEC 9574 : 1992 (E) - CCIIT 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. - CCIlT Recommendation X.30
19、 (1.462) (1988), Support of X.21, X.21 bis and X.20 bis bused dutu terminal equipments (DTEs) by an integrated services digital network (ISDN). - CCITT Recommendation X.31 (1.462) (1988), Support of Packet Mode Terminal Equipment by un ISDN. - CCIlT Recommendation X.32 (1988), Interface between data
20、 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 ISDN or a circuit switched public data network. - IS0 7776: 1986, Information proces
21、sing systems - Data communications - High-level duta link control procedures - Description of the X.25 LAPB-compatible DTE data link procedures. - ISOIIEC 8208: 1990, Information technology - Data communications - X.25 Packet Luyer Protocol for Data Terminal Equipment. 3 Definitions For the purposes
22、 of this Recommendation I International Standard, the following definitions apply. 3.1 Basic reference model definitions This Recommendation I International Standard makes use of the following terms defined in CCITT Recommendation X.200 I IS0 7498: a) Network Connection; b) Network Layer; c) Network
23、 Service. 3.2 Service conventions definitions This Recommendation 1 International Standard makes use of the following terms defined in CCITT Recommendation X.2 10 I ISOKR 8509: a) Network Service provider; b) Network Service user. 3.3 Network service definitions This Recommendation I International S
24、tandard makes use of the following terms defined in CCITT Recommendation X.213 I ISO/IEC 8348: a) N-CONNECT request; b) N-DISCONNECT indication. 3.4 X.25 definitions This Recommendation I International Standard makes use of the following terms defined in CCITT Recommendation X.25 I ISO/IEC 8208: a)
25、DATA packet; b) Data terminal equipment; c) INCOMING CALL packet; CCITT Rec. X.612 (1992 E) 3 ISO/IEC 9574 : 1992 (E) d) Throughput class; e) User data field; 3.5 X.31 definitions This Recommendation 1 International Standard makes use of the following terms defined in CCITT Recommendation X.3 1: a)
26、Conditional notification class of service; b) ISDN Virtual Circuit Bearer Service; c) No notification class of service; d) Packet handling function; e) PSPDN Service; f) Unconditional class of service; g) Semi-permanent-access (see Note); h) Demand access. NOTE - Some ISDN Recommendations use the te
27、rm permanent to describe this feature. 3.6 I.1 12 definitions This Recommendation 1 International Standard makes use of the following terms defined in CCITT Recommendation I. 112: a) terminal equipment; b) reference point. 3.7 I.411 definitions This Recommendation 1 International Standard makes use
28、of the following terms defined in CCITT Recommendation I.41 1: a) R reference point; b) S reference point; c) T reference point; d) Terminal adaptor. 3.8 I.412 definitions This Recommendation 1 International Standard makes use of the following terms defined in CCITT Recommendation 1.412: a) B channe
29、l; b) D channel. 4 CCIIT Rec. X.612 (1992 E) ISO/IEC 9574 : 1992 (E) 3.9 X.121 definitions This Recommendation 1 International Standard makes use of the following terms defined in CCITT Recommendation X. 12 1: a) prefix; b) escape. 4 Abbreviations 4.1 Reference model abbreviations OS1 Open Systems I
30、nterconnection NS Network Service 4.2 Network service abbreviations CONS Connection-mode Network Service QOS Quality of service 4.3 X.25 abbreviations DCE Data circuit-terminating equipment DTE Data terminal equipment LAP link access procedure PLP Packet layer protocol PSDN Packet switched data netw
31、ork RPOA Recognized private operating agency 4.4 ISDN abbreviations AU Access unit ISDN Integrated services digital network PH Packet handling function SAPI Service access point identifier TA Terminal adaptor TE Terminal equipment HLC Higher layer compatibility 5 Overview 5.1 ISDN environment The IS
32、DN environment is characterised by two configurations. In the first, a packet mode terminal is connected to a packet mode service, as described in Recommendation X.31. In the second configuration, two packet mode terminals are connected directly by an ISDN circuit-switched B or H channel. CCIIT Rec.
33、 X.612 (1992 E) 5 ISO/IEC 9574 : 1992 (YE) 51.1 Use of a packet mode service The support of the packet mode terminal equipment by an ISDN when a packet mode service is used is described in Recommendation X.31. In this case, references to Recommendation Q.931 procedures indicate their use as describe
34、d in Recommendation X.31. Two cases for ISDN support of packet mode terminal equipment are defined in Recommendation X.31: one, the case where the support is via the ISDN Virtual Circuit service see Figure la), and the other where the support is via access to PSDN services see Figure lb), respective
35、ly referred to as “case B” and “case A”. In case A an ISDN transparent circuit connection, either semi-permanent (i.e., non-switched) or demand (i.e., switched), is used. The corresponding ISDN bearer service is a 64 kbit/s service as described in Recommendation 1.231. The sub-network functions avai
36、lable to the user are those of the PSDN described in Recommendation X.25 (semi-permanent access) and Recommendation X.32 (demand access), as well as in other X-Series Recommendations (e.g., X.2, X.121). In case B the ISDN virtual circuit bearer service is used, as described in Recommendation 1.232.
37、The sub-network functions available are those described in the 1.2xX-Series Recommendations. In case A only B channels may be used to access the PSDN, while in case B both B and D channels may be used to access the ISDN packet handling function. 5.1.2 Direct circuit-switched connection Two packet mo
38、de terminal equipment may be connected directly using an ISDN B or H channel. The channel used is either semi-permanent (i.e. non-switched) or demand (i.e. switched), see Figure lc). 5.2 CONS in this ISDN environment Recommendation X.223 I IS0 8878 specifies the method for providing the OS1 Connecti
39、on-mode Network Service (CONS) through the use of the X.25 packet layer protocol. When operating in an ISDN environment, a few requirements additional to those contained in Recommendation X.223 I IS0 8878 are necess,ary. The requirements for providing CONS by terminal equipment connected to an ISDN
40、at the S or T reference points are specified in clause 6. The requirements for providing CONS in X.25 DTEs presenting an X.21, X.21 his, or V.25 bis interface at the R reference point and connected to an ISDN through a TA are specified in clause 7. This Recommendation International Standard uses the
41、 X.25 PLP to convey all elements, of all three phases, of the OS1 Connection-mode Network Service. 6 Provision of the CONS in systems attached at the S/T reference point 6.1 Procedures for TEls or TE2/TAs to provide CONS This clause of this Recommendation International Standard covers the five cases
42、 that exist taking into account the various types of underlying connections that can be available to the packet mode TEl or TE2/TA (see Table 1). The protocol layers applicable to these cases are given in Figures 2 and 3 and as referenced in Table 1. The mapping of the elements of the CONS to the protocol and procedures of ISO/IEC 8208 shall be as required by Recommendation X.223 I IS0 8878. The remaining clauses in this section specify the provisions required in addition to these mappings, by systems attached to an interface at the S/T reference point. 6 CCITT Rec. X.612 (1992 E)
