1、CCITT RECMN*X=b12 92 48b2591 0574983 bb4 = INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE DATA COMMUNICATION NETWORKS X.612 (09192) INFORMATION TECHNOLOGY - PROVISION OF THE OS1 CONNECTION-MODE NETWORK SERVICE BY PACKET-MODE TERMINAL EQUI
2、PMENT CONNECTED TO AN INTEGRATED SERVICES DIGITAL NETWORK (ISDN) Recommendation X.612 Geneva, 1992 Foreword I“U (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The CCIT (the International Telegraph and Telephone Consultative Commit
3、tee) is a permanent organ of the ITU. Some 166 member couniries, 68 telecom operating entities, 163 scientific and industrial organizations and 39 international organizations participate in CClT which is the body which sets world telecommunications standards (Recommendations). The approval of Recomm
4、endations by the members of CCIT is covered by the procedure laid down in CC Resolution No. 2 (Melbourne, 1988). In addition, the Plenary Assembly of CCIT, which meets every four years, approves Recommendations submitted to it and establishes the study programme for the following period. In some are
5、as of infomation technology which fall within CClTs purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. The text of CC Recommendation X.612 was approved on 1otb September 1992. The identical text is also published as ISO/IEC Inmational Siandard 9574. CCIIT NOTE I
6、n this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication Administration and a recognized vate operating agency. O IT 1992 Ail rights reserved. No patt of this publication may be reproduced or utilized in any form or by any means, electronic
7、or mechanical, including photocopying and microfilm, without permission in writing km the ITU. CCITT RECMN*X.b12 92 m 48b259L 0574985 437 m ISOKEC 9574 : 1992 (E) INTERNATIONAL STANDARD CCIT RECOMMENDATION INFORMATION TECHNOLOGY - PROVISION OF THE OS1 CONNECTION-MODE NETWORK SERVICE BY PACKET-MODE T
8、ERMINAL EQUIPMENT CONNECTED TO AN INTEGRATED SERVICES DIGITAL NETWORK (ISDN) 1 Scope This Recommendation I International Standard specSies the method of providing the OS1 Connection-mode Network Service (CONS) by packet mode terminal equipment conneced to an Integrated Services Digital Network (ISDN
9、) in accordance with the procedures described in Recommendation X.3 1. This is done by specifying the mapping of the CONS primitives and parameters to and from the elements of the protocols used by two types of packet mode teminal equipment: a) an X.25 DTE (E2) connected to an R reference point and
10、accessing an ISDN; and b) a packet mode ISDN terminal (TEl) operating ISO/IEC 8208 packet layer protocol (PLP) and connected to an ISDN at either the S or T reference point. This Recommendation I Intemational Standard is applicable: a) b) when operating according to Recommendation X.31, either a TE1
11、 or a TE2 is connected to a packet handier in an ISDN or an access unit to a packet-switched data network via an ISDN; when using an ISDN circuit-switched channel, either TEls and/or “E2lIAs are connected directly to each other (i.e. the terminals operate in DTE/DTE mode). This Recommendation I Inte
12、rnational 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.613 I ISO/IEC 10588). NOTES 1 The definitions of TE1, TE2 and TA equipment, and R, S, and T reference points
13、are given in Recomenda- tionI.411. 2 This Recommendation I International Standard applies to a TE1 or TE2A (i.e. an OS1 End System) regardiess of whether it is a physically separate system or embedded in other equipment such as a PBX. This Recommendation I International Standard addresses the provis
14、ion of the CONS using Virtuai Calls as described in Recommendation X.25. It does not address the use of X.25 Permanent Virtuai Circuits, The extension of this Recommendation I International Standard to include the use of X.25 PVCs is for further study. NOTE -This Recommendation I International Stand
15、ard 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 reference model of open systems int
16、erconnection. 1 CCIIIT Rec. X.612 (1992 E) CCITT RECNN*X*bL2 92 48b259L 057498b 373 ISO/IEC 9574 : 1992 ) 2 Normative references The foilowing CC Recommendations and ISO/EC International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation
17、I International Standard. At the time of publication, the editions indicated were valid. Ali Recommendations and Standards are subject to revision. Parties to agreements based on this Recommendation I International Standard are encouraged to investigate the possibility of applying the most recent ed
18、itions of the Recommendations and Standards listed below. Members of IEC and IS0 maintain registers of currently valid Intemational Standards. The CC Secretariat maintains a list of currently valid CCI“ Recommendations. 2.1 Identical Recommendations I International Standards - CC Recommendation X.21
19、3 (1992) I ISO/IEC 8348: 1992, Information technology - Network service dejnition for Open Systems Interconnection 2.2 Paired Recommendations I International Standards equivalent in technical content - CCITT Recommendation X.200 (1988), Reference model of open systems interconnection for CClT applic
20、ations. IS0 7498: 1984, Information processing systems - Open Systems Interconnection - Basic Reference Model. - CC Recommendation X.210 (1988), Open systems interconnection Zayer service definition conventions. ISOR 8509:1987, Information processing systems - Open Systems Interconnection - Service
21、conventions. - CC Recommendation X.223 (1988), Use of X.25 to provide the OSI connection-mode network service for CCITapplications. IS0 8878: 1987, Information processing systems - Data communications - Use of X.25 to provide the OS1 connection-mode network service. 2.3 Additional references CCI“ Re
22、commendation 1.23 1 (1988), Circuit-mode bearer service categories. CC Recommendation 1.232 (1988), Packet-mode bearer service categories. CC Recommendation 1.430 (1988), Basic User-Network Interface Layer I Specifcation. CCITT Recommendation 1.43 1 (1988), Primary Rate User-Network Interface Layer
23、I Specifcation. CCT Recommendation Q.921 0.441) (1988), ISDN User-Network Interface Data Link Layer Specification. CC Recommendation Q.931 (.451) (1988), ISDN User-Network Interface Layer 3 Specflcarion for Basic Call Control. CCIT Recommendation V.25 bis (1988), Automatic Answering Equipment dor Pa
24、rallel Automatic Calling Equipment on the General Switched Telephone Network Including Procedures for Disabling of Echo Control Devices for Both Manually and Automatically Established Calls. CCIT Recommendation X.21 (1988), Interface Between Data Terminal Equipment (DTE) and Data Circuit-terminating
25、 Equipment (DCE) for Synchronous Operation on Public Data Networks. CC 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. X.612 (1992 E) CCITT RECMN*XmbL2 92 4862593 0574987 20T D
26、 Isomc 9574 : 1992 (E) - CCIT Recommendation X.25 (1988). Interface between data terminal equipment TE) and data circuit-terminating equipment CE) for terminais operating in the packet mode and connected to public data networks by dedicated circuit. CCIT Recommendation X.30 (I.462) (1988), Support o
27、f X.21, X.21 bis and X.20 bis based data terminal equipments (DTEs) by an integrated services digital network (ISDN). CC Recommendation X.31 (1.462) (1988). Support of Packet Mode Terminal Equipment by an ISDN. CCm Recommendation X.32 (1988). Inteeace between daru termiml equipment (DTE) and data ci
28、rcuit-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 processing systems - Data communications - Hig
29、h-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. - - - - - 3 Definitions For the purposes of this Recommendation I Intern
30、ational Standard, the following definitions apply. 3.1 Basic reference model definitions This Recommendation I International Standard makes use of the following terms defined in CCm Recommendation X.200 I IS0 7498: a) Network Connection; b) Network Layer; c) Network Service. 3.2 Service conventions
31、definitions This Recommendation I International Standard makes use of the foiiowing terms defined in CC Recommendation X.210 I ISO/TR 8509: a) Network Service provider; b) Network Service user. 3.3 Network service definitions This Recommendation I International Standard makes use of the following te
32、rms defined in CCIT Recommendation X.213 I ISO/IEC 8348: a) N-CONNECT request; b) N-DISCON“ indication. 3.4 X.25 definitions This Recommendation I International Standard makes use of the following terms defined in CCIT Recommendation X.25 I ISO/IEC 8208 a) DATA packet; b) Data terminal equipment; c)
33、 INCOMING CALL packet; CCFIT Rec. X.612 (1992 E) 3 CCITT RECNN*X*bJ2 72 m 48b259L 0574988 146 m ISO/IEC 9574 : 1992 (E) d) Throughput class; e) Userdatafield; 3.5 X.31 definitions This Recommendation I International Standard makes use of the foilowing terms defined in Recommendation X.3 1: a) Condit
34、ional 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 term per
35、manent to describe this feature. 3.6 1.1 12 definitions This Recommendation I International Standard makes use of the following terms defined in Recommendation 1.1 12 a) terminal equipment; b) referencepoint. 3.7 1.411 definitions This Recommendation I International Standard makes use of the followi
36、ng terms defined in Recommendation 1.411: a) R reference point; b) S reference point; c) T reference point; d) Terminal adaptor. 3.8 1.412 definitions This Recommendation Recommendation 1.4 12 a) Bchannel; b) Dchannel. Internationai Standard makes use of the following terms defined in ccm ccm ccm cc
37、m 4 CCK Rec. X.612 (1992 E) CCITT RECMN*X*bL2 92 m 48b259L 057Y989 O2 m ISO/EC 9574 : 1992 (E) 3.9 X.121 definitions This Recommendation I International Standard makes use of the following terms defined in CCI?T Recommendation X .12 1 : a) prefur; b) escape. 4 4.1 4.2 4.3 4.4 5 5.1 Abbreviations Ref
38、erence model abbreviations OS1 Open Systems Interconnection NS Network Service Network service abbreviations CO“ Connection-mode Network Service QOS Quality of service X.25 abbreviations DCE Data circuit-terminating equipment DTE Data terminal equipment LAP link access procedure PLP Packet layer pro
39、tocol PSDN Packet switched data network RPA Recognized private operating agency ISDN abbreviations AU Access unit ISDN Integrated services digital network PH Packet handling function SAP1 Service access point identifier TA Terminal adaptor TE Terminal equipment HLC Higher iayer compatibility Overvie
40、w ISDN environment The ISDN 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
41、 or H channel. CCITT Rec. X.612 (1992 E) 5 CCITT RECNN*X*b12 92 = 4862591 0574990 8T4 Isomc 9574 : 1992 (E) 5.1.1 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
42、 to Recommendation 4.931 procedures indicate their use as described 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 Vial Circuit service see Figure la), and the other where the su
43、pport is via access to PSDN services see Figure lb), respectively referred to as “case By and “case A”. In case A an ISDN transparent circuit connection, either semi-permanent (Le., non-switched) or demand (i.e., switched), is used. The corresponding ISDN bearer service is a 64 kbit/s service as des
44、cribed in Recommendation 1.231. The sub-network functions available 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 virtuai circuit
45、bearer service is used, as described in Recommendation 1.232. The sub-network functions available are those described in the 1.2-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 func
46、tion. 5.13 Direct circuit-switched connection Two packet mode terminal equipment may be connected directly using an ISDN B or H channel. The channel used is either semi-permanent (Le. non-switched) or demand (Le. switched), see Figure lc). 5.2 CONS in this ISDN environment Recommendation X.223 I IS0
47、 8878 specifies the method for providing the OS1 Connection-mode Network Service (CONS) through the use of the X.25 packet layer protocol. When operating in an ISDN environment, a few requirements additionai to those contained in Recommendation X.223 I IS0 8878 are necessary. The requirements for pr
48、oviding CONS by terminal equipment connected to an ISDN 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 bis, or V.25 bis interface at the R reference point and 0eck.d to an ISDN through a TA are specified in clause 7
49、. This Recommendation I International Standard uses the X.25 PLP to convey all elements, of all thtee phases, of the OS1 Connection-mode Network Service. 6 Provision of the CONS in systems attached at the S” reference point 6.1 Procedures for TEls or TEWTAs to provide CONS This clause of this Recommendation I International Standard covers the five cases that exist taking into account the various types of underlying connections that can be available to the packet mode TE1 or (see Table i). The protocol layers a
