1、CCITT RECMN*X-b14 72 4862571 0575019 Y18 INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE DATA COMMUNICATION NETWORKS X.614 (09/92) INFORMATION TECHNOLOGY - USE OF X.25 PACKET LAYER PROTOCOL NETWORK SERVICE OVER THE TELEPHONE NETWORK TO PRO
2、VIDE THE OS1 CONNECTION-MODE Recommendation X.614 CCITT RECMN*X=bL4 92 4662593 0575020 L3T Foreword I“J (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The CC (the International Telegraph and Telephone Consultative Committee) is a
3、permanent organ of the . Some 166 member countries, 68 telecom operating entities, 163 scientific and industrial organizations and 39 international organiz,ations participate in CC which is the body which sets world telecommunications standards (Recommendations). The approval of Recommendations by t
4、he members of CC is covered by the procedure laid down in CC“T Resolution No. 2 (Melbourne, 1988). In addition, the Plenary Assembly of CC, which meets every four years, approves Recommendations submitted to it and establishes the study programme for the following period. In some areas of informatio
5、n technology, which fall within CcITTs purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. The text of CC Recommendation X.614 was approved on 10 September 1992. The identical text is also published as ISOiiE! International Standard 10732. CcI?T NOTE In this Reco
6、mmendation, the expression “Administration“ is used foi conciseness to indicate both a telecommunication Administration and a recognized private operating agency. O IT 1993 Ali rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mecha
7、nical, including photocopying and microfilm, without permission in writing from the TIT. CCITT RECNN*X-bLY 92 m Y862591 0575023 07b m 1 2 3 4 5 6 7 8 Contents Page scope 1 . . I Normative references 1 2.1 Identical Recommendations I International Standards 1 Paired Remmendations I International Stan
8、dards equivalent in technical content. 2.2 2.3 Additional references Definitions 1 2 . 2 3.1 Reference model deftnitions 2 3.2 Service conventions definitons . 2 3.3 Network service definitons . 2 3.4 X.25 definitions 2 Abbreviations . 3 4.1 Reference model abbreviations 3 4.2 Network service abbrev
9、iations . 3 4.3 X.25 abbreviations 3 4.4 Other abbreviations . 3 Overview . 3 Control of underlying connections . 5 6.1 Leased circuit connection 5 6.2 Switched connection . 5 Data link layer . 6 7.1 Mode of protocol . 6 7.2 Address assignment 6 7.3 Parameter values 6 Packet layer . 6 8.1 General 6
10、. . . . 8.2 Addressing 7 8.3 QS parameters 7 8.4 Window size and packet size parameters . 7 8.5 Logical channel ranges 7 8.6 Role selection 7 Annex A Bibliography . 8 I I CCITT RECMN*X*b14 32 m 4862591 0535022 TO2 m ISOAEC 10732 : 1993 (E) INTERNATIONAL STANDARD CCI“ RECOMMENDATION INFORMATION TECHN
11、OLOGY - USE OF X.25 PACKET LAYER PROTOCOL TO PROVIDE THE OS1 CONNECTION-MODE NETWORK SERVICE OVER THE TELEPHONE NETWORK 1 Scope This CC Recommendation I International Standard is applicable to the environments where the X.25 packet layer protocol, as standardized in (PLP) ISO/iEC 8208, is operated o
12、ver a telephone network connection to provide the OS1 Connection-mode Network Service (CONS). These environments include a) b) c) d) This provision is achieved by specifying the mapping of the CONS primitives and parameters to and from the elements of the protocols used. telephone network leased cir
13、cuit connection between two DTEs; telephone network switched connection between two DTEs; DTE access to a PSDN via a telephone network leased circuit connection; and DTE access to a PSDN via a telephone network switched connection. 2 Normative references The following CCITI Recommendations and Inter
14、nationai Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation I International Standard. At the time of publication, the editions indicated were valid. Ail Recommendations and Standards are subject to revision and parties to agreements based
15、 on this Recommendation I Internationai Standard are encouraged to investigate the possibility of applying the most recent edition of the Recommendations and Standards listed below. Members of IBC and IS0 maintain registers of currently valid International Standards. The CC Secretariat maintains a l
16、ist of the currently valid CCI“ Recommendations. 2.1 Identical Recommendations I Internationai Standards - CCIIT Recommendation X.213 (1992) I ISO/IEC 8348:1993, Information technology -Network service demition for Open Systems Interconnection. 2.2 Paired Recommendations I International Standards eq
17、uivalent in technical content - CC Recommendation X.200 (1988), Reference Model of Open Systems Interconnection for CCIIT Applications. IS0 7498:1984, Information processing systems - Open Systems Interconnection - Basic Reference Model. CCIIT Recommendation X.210 (1988), Open Systems Interconnectio
18、n Layer Service Definition Conventions. ISOfR 8509: 1987, Information processing systems - Open Systems Interconnection - Service Conventions. CC Recommendation X.223 (19881, se of X.25 to provide the OSI connection-mode network service for CCITT applications. IS0 8878:1987, Information processing s
19、ystems - Data communications - Use of X.25 to provide the OS1 Connection-Mode Network Service. - - CCI“ Rec. X614 (1992 E) 1 CCITT RECMN*X-b14 92 = 4862591 0575023 949 m ISOAEC 10732 : 1993 (E) 2.3 Additional references - CCITT Recommendation V.25 (1988), Automatic answering equipment dor parallel a
20、utomatic calling equipment on the general switched telephone network including procedures for disabling of echo control devices for both manually and automutically established calls. CC Recommendation V.25 bis (1988), Automutic calling dor answering equipment on the general switched telephone networ
21、k (GSnV) using the 100-Series interchange circuits. CC 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. CC Recommendation X.3
22、2 (1988), Interface between 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 swi
23、tched public data network. IS0 77761986, In$ormation processing system - Data communication - High-level data link control procedures -Description of the X25 LAPB-compatible DTE datu link. procedures. ISO/IEc 8208:1990, Information technology - Data communications - X25 Packet Layer Protocol for Dat
24、a Terminal Equipment. - - - - - 3 Definitions For the purposes of this Recommendation I International Standard, the following definitions apply. 3.1 Reference model definitions This Recommendation I International Standard makes use of the following terms defined in CCIT Recornmen- datim x.200 I IS0
25、7498 a) Network Connection; b) NetwmkLayer; c) Network Service. 3.2 Service conventions definitions This Recommendation I Intemational Standard makes use of the following terms defined in CCI“ Recommen- dation X.210 I ISOm 8509. a) Network Service provider; b) Network Service user. 3.3 Network servi
26、ce definitions This Recommendation I International Standard makes use of the following terms defined in CC Recommen- dation X.213 I ISO/IEC 8348 a) N-CONNECT request; b) N-DISCONNECT mdication. 3.4 X.25 definitions This Recommendation I International Standard makes use of the following terms dened i
27、n CCIT Recornmen- dation X.25 and ISO/IEC 8208: a) Data circuit-temhath g equipment; b) Data terminal equipment; c) Registration packet; d) Virtualcall. 2 CCm Rec. X.614 (1m E) CCITT RECMN*X-bLY 72 = 4862571 0575024 885 = 4 4.1 4.2 4.3 4.4 5 There are two basic configurations where the X.25 packet l
28、ayer protocoi (PLP), as standardized in ISOEC 8208, may be operated over a telephone network connection to provide the OS1 Connection-mode Network Senrice (CONS) defined in CCIIT Rec. X.213 I ISO/IEC 8348. The first configuration is shown in Figure la) where two X.25 DTEs are directly connected by a
29、 telephone network connection. In this case each DTE operates the D“IYDTE mode of ISOlIEC 8208 (X.25 PLP) and IS0 7776 (X.25 LAPB). Ibe telephone network connection may be a leased circuit or switched. The second configuration is shown in Figure lb) where an X.25 DTE accesses a PSDN. In this case th
30、e DTE operates the DTE/DCE mo b) an exchange is always needed between the two DTEs; or c) the need, or lack of need, of an exchange depends on other factors known to the two DTEs. For the mode of operation where a switched telephone network connection is used to connect a DTE and a DCE, the need for
31、 an identification exchange is governed by the PSDN requirements and the PSDN services the DTE desires to use (services are defined in Recommendation X.32). Wen an exchange of identification information is needed, the method(s) of exchange wiil be selected from the methods given in Recommendation X.
32、32 (see the Note below). For DTE-to-DTE operation, the method is agfeed between the two DTEs on an a prion basis. For DTE-to-DCE operation, the requirements of the PSDN will govern which method is to be used. NOTE - Although Rtcommendation X.32 spiles the identification procedures as DTB-to-DCE, the
33、y are qpkd to the DTE-to-DTE case by this Recommendation I International Standard. 7 Data link layer 7.1 Mode of protocol The bask mode (modulo 8) single Link procedures sba be implemented. The extended mode (moduio 128) single link procedure may also be implemented. 7.2 Address assignment For DTEi-
34、to-DTE operation over aswitched umnection and for DTE access to a PSDN via a switched Connection, the A and B addresses of IS0 7776 shall be determined as follows: the calling end is assigned address A and the caiied end is assigned address B unless the assignment is known a priori. For access to a
35、PSDN via a leased circuit, the A and B addresses shall be as specified in Recommendation X.25. For DTE-to-DTE Operation over a leased circuit, the A and B addses shall be known apriori. 73 Parametervalues It is recommended that the T1 her be capable of Wig set to a value of 5 s in order to cope with
36、 multiple satellite links. It is recommended that 1 03 1 octet frames be supported in order to accommodate satellite connections. (modulo 128) operaiion may be advisable, particularly if multiple satellite hops are likely. NOTE - In addition to these recommendations, the use of large windows, requir
37、ing the use of extended mode 8 Packet layer 8.1 General In general the fea- defined in CCI“ Rec. X.223 I IS0 8878 apply with regards to the QOS parameters and addressing. The following additional considerations apply to the operation of some specific mechanisms in Recom- mendations X.25 and X.32. 6
38、CCm Rec. X.614 (1992 E) CCITT RECMN*X*hL4 92 m 48b259L 0575028 420 m IsO/lEC 10732 : 1993 (E) 8.2 Addressing 8.2.1 DTEto-DTE Configuration Telephone network addressing is used to establish the telephone network connection between the two concerned SNPAS. The X.25 Address Field is not used (i.e. it i
39、s empty) in this case, and the Called and Calling NSAP addresses are entirely conveyed in the Called and Calling Address Extension facilities. If packets are received which contain addressing mfomtion in the Address Field, this information sha be ignored. 8.23 DTE-to-DCE Configuration Telephone netw
40、ork addressing is used to establish the telephone network connection between the two concerned SNPAs (i.e. the DTE and the PSDN). The X.25 Address Field and the Called and Calling Address Extension facilities are used as defined in CCm Rec. X.223 I IS0 8878. 8.3 QOSparameters 8.3.1 Throughput QOS pa
41、rameters The calling NL entity should have an u priori knowledge of the data signalling rate employed by the modems operating over the telephone network. This knowledge is used to determine the value of the throughput and to determine if a new telephone network connection is to be established to mee
42、t the NS user requirements. 8.33 Transit delay QOS parameter Due to the limited signaliiig capabilities of the telephone network, the calling NL entity should have an u priori knowledge of the transit delay of the connection. This u priori knowledge may be obtained via knowledge of the network topol
43、ogy or via monitoring of the connection characteristic. The value of the telephone network aansit delay is used as part of the calculation in determining the cumulative transit delay carried in the End-teEnd Transit Delay Negotiation facility (see CCIT Rec. X.223 I IS0 8878). 8.4 Window size and pac
44、ket size parameters If only one virtual circuit is to be used, an appropriate window size should be supported. NOTE - For consistency with protocol implementations operating over other types of transparent connections, it may be desirable to support 1024 octet data packets. 8.5 Logical channel range
45、s The logical channel ranges &IC, HIC, LTC, HTC, LOC and HOC in ISO/IEC 8208) to be used are determined by local knowledge if available. If local knowledge is not available, then only a single two-way logical channel is available and LTC and HTC shall be set to 1. If additionai logical channels are
46、required, they may be negotiated by using the Registration packet as described in ISO/IEC 8208. In order to avoid collision of Registration packets, the circuit initiator is responsible for initiating the negociation. 8.6 Role selection In the absence of u priori knowledge, the Restart procedure sha
47、ll be used for role selection as described in ISO/IEC 8208. CCFZT Rec. X.614 (1992 E) 7 CCITT RECMN*X.b34 92 4862593 0575029 3b7 ISOAEC 10732 : 1993 (E) Annex A Bibliography (“lis amex does not form an integrai part of this Recommendation I International Standard.) Additional references CCT Recommen
48、dation X.610 (1992), Provision and suppon of the OSI connection-mode network service. ISO/IEC 8880-2 1992, Information technology - Telecommunications and information exchange between systems - Protocol combinations to provide and support the OSI Network Service - Part 2: Provision and support of the connection-mode Network Service. - - 8 CCllT Rec. X.614 (1992 E)
