1、CCITT RECMN*X*hL3 92 = 4862593 0575004 T97 INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE DATA COMMUNICATION NETWORKS X.613 (09/92) INFORMATION TECHNOLOGY - USE OF X.25 PACKET LAYER PROTOCOL IN CONJUNCTION WITH X.21X.21 bis TO NETWORK SER
2、VICE PROVIDE THE OS1 CONNECTION-MODE Recommendation X.613 CCITT RECMN*X-bL3 92 m 4862593 0575005 923 m Foreword IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The CC (the International Telegraph and Telephone Consultative Commi
3、ttee) is a permanent organ of the ITU. Some 166 member countries, 68 telecom operating entities, 163 scientific and industrial organizations and 39 international organizations participate in CCITT which is the body which sets world telecommunications standards (Recommendations). The approval of Reco
4、mmendations 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 CC, 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 information technology, which fall within CCI”s purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. The text of CC Recommendation X.613 was approved on 10th of September 1992. The identical text is also published as ISO/IEC International Standard 10588. CCT
6、 NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. O ITU 1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means,
7、electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. CCITT RECHN*X=bL3 92 W 4Bb2591 057500b BbT W 1 2 3 4 5 6 7 Contents Page . 1 scope Normative . 1 I 2.1 Identical Recommendations I International Standards 1 Paired Recommendations I Internatio
8、nal Standards equivalent in technid content . 2.2 1 2.3 Additional references ,. 2 2 efinitinna . , I-.-“ 2 2 3.1 Reference model definitions 3.2 Service umventions definitions . 3.3 Network Service definis.,., 2 3.4 X.25 definitions 3 3.5 X.21 definitions 3 3.6 ISDN definitions . 3 Abbreviations 3
9、4.1 Reference model abbreviations . 3 4.2 Network service abbreviations 3 4.3 X.25 abbreviations 3 4.4 ISDN abbreviations . 4 4.5 other abbreviations . 4 Overview . 4 Control of underlying connections . 5 6.1 Leased circuit connection 6 6.2 Circuit switched connection (including direct cail) . 6 - D
10、ata link layer . 8 -_ _ - - - 7.1 Mode of protocoi 8 7.2 Address assignment . 8 7.3 Parameter values . 8 CCITT RECMN*X-b13 92 W 4Bb259L 0575007 7Tb 8 Packet iayer . 8.1 8.2 8.3 8.4 8.5 8.6 Annex A Annex B General . Addressing QS parameters Window size and packet size parameters . Logical channel ran
11、ges . Role selection . X.30 Terminal adaptors for ISDN . Bibliography . 8 8 8 9 9 9 9 10 11 CCITT RECMN*X*bL3 92 m 48b259L 0575008 632 m ISo/IEC 10588 : 1993(E) INTERNATIONAL STANDARD CC RECOMMENDATION INFORMATION TECHNOLOGY - USE OF X.25 PACKET LAYER PROTOCOL IN CONJUNCTION WITH X.2vX.21 bis TO PRO
12、VIDE THE OS1 CONNECTION- MODE NETWORK SERVICE 1 Scope This CCI“ Recommendation I Intematid Standard is applicable to the environments where Recornmetidation X.21 or X.21 bis is used and where the X.25 packet layer protocol (PLP), as standardized in ISO/IEC 8208, is operated during the X.21Bc.21 bis
13、data phase to provide the OS1 Connection-mode Network Service (CONS). These environments include a CSDN and an ISDN Terminal Adaptor complying with Recommendation X.30 which provides an X.21 access. The X.25 PLP operates either in the DTEIDTE or DTB/DCE mode. This provision is achieved by specifying
14、 the mapping of the CONS primitives and parameters to and from the elements of the protocols used 0.e. X.25 PLP and X.21). 2 Normative references The following CCI“ Recommendations and Inmational Standards contain provisions which, through reference in this text, constitute provisions of this Recorn
15、meridation I International Standard. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject to revision and parties to agreements based on this Recommendation I International Standard are encouraged to investigate the possibility of applying the
16、most recent edition of the Recommendations and Siandards listed below. Members of IEC and IS0 maintain registers of currently valid Internationat Standards. The CCITT Secretariat maintains a list of the currently valid CClTT Recommendations. 2.1 Identical Recommendations I International Standards -
17、CCITT Recommendation X.213 (1992) I ISOE 8348: 1993, Informution technology - Network service definition for Open Systems Interconnection 2.2 Paired Recommendations I International Standards equivalent in technical content - CCIiT Recommendation X.200 (1988), Reference Model of Open Systems Intercon
18、nection for CCK Applications. IS0 7498 1984, Information processing systems - Open Systems Interconnection - Basic Reference Model. CCITT Recommendation X.210 (1988), Open Systems Interconnection Layer Service Dejnition Conventions. ISOKR $509: 1987, Infomion processing systems - Open Systems Interc
19、onnection - Service conventions. - - CC Recommendation X.223 (1988), Use of X.25 to provide the OSZ Connection-Mode Network Service for CCITT applicat(0ns. IS0 8878:1987, Information processing systems - Data Communications - Use of X.25 to provide the OS1 Connection-Mode Network Service. CCl“ Rec.
20、X.613 (1992 E) 1 CCITT RECMN*X-bL3 92 m 4862593 0575009 579 m ISO/IEC 10588 : 1993(E) 2.3 Additional references CCIT Recommendation X.2 (1988), International data transmission services and optional user facilities in public data networks and ISDNs. CC Recommendation X.21 (1992), Interface between da
21、ta terminal equipment and data circuit- terminating equipment for synchronous operation on public data networks. CCI“ 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. CCIlT Recommendation X.
22、25 (1988), Interface beween 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.30 (1988), Support of X.21, X.21 bis and X.20 bis based data terminal equi
23、pments (DTEs) by an integrated services digital network (ZSDN). CCITT Recommendation X.31 (1988), Support of packet mode terminal equipment by an ISDN. CC Recommendation X.32 (1988), Interface between data terminal equipment (DTE) and data circuit-terminuthg equipment (DCE) for terminals operating i
24、n 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 nenvork. IS0 77761986, Information processing systems - Data communication - High-level data link control proc
25、edures - Description of the X.25 LAPB-compatible DTE data link procedures. ISO/IEC 82081990, lnfornuuion technology - Data communications - X.25 Packet mer Protocol for Data Terminal Equipment. 3 DefillitiOllS For the purposes of this Recommendation I International Standard, the following definition
26、s apply. 3.1 Reference model definitions This Recommendation I International Standard makes use of the following terms defined in CCIIT Recommen- dation XSOO I IS0 7498 a) Network Connection; b) NetworkLayer, c) Network Service. 3.2 Service conventions defnitions This Recommendation i International
27、Standard makes use of the following terms defined in CU“ Recommen- dation X210 I ISOR 8509: a) Network Service pmvidec b) Network Service user. 3.3 Network Service definitions This Recommendation I International Standard makes use of the following terms defined in CC Recommen- dation X.213 I ISO/IEC
28、 8348 a) N-CONNECTrequesC b) N-DISCONNECT hdicatiOn. 2 CCm Rec. X.613 (1992 E) ISOiEC 10588 : 1993tE) 3.4 X.25 definitions This Recommendation I International Standard makes use of the following terms defined in CClT Rmmmen- dation X.25 and ISOWC 8208: a) Data circuit-terminating equipment; b) Data
29、terminal equipment; c) Registration packet; d) Virtualcail. 3. X.21 definitions This Recommendation I International Standard makes use of the following term defined in CCITT Recommen- dation x.21: Call progress signal. 3.6 ISDN definitions mis Recommendation I International Standard makes use of the
30、 following tew defined in CCI“ Recmmen- dation X.31: 4 4.1 4.2 4. Terminal adaptor. Abbreviations Reference model abbreviations NL Network Layer NS Network Service os1 Open Systems Interconnection Network service abbreviations CONS Connection-mode Network Service NSAP Network service access point Qo
31、s Quality of service SNPA Subnetwork point of attachment X.25 auwreviations DCE Data circuit-terminating equipment DTE Data terminal equipment HIC Highest incoming channel HOC Highest outgoing channel m Highest two-way channel LAPB Link CCSS procedure - balaiiced LIC Lowest incoming channel LOC Lowe
32、st outgoing channel LTC Lowest two-way channel PLP Packet layer protocol CCT Rec. X.613 (1992 E) 3 CCITT RECMN*X*bL3 92 4862591 0575011 127 BOLEC 10588 : 1993) 4.4 ISDN abbreviations ISDN Integrated services digitai network IWF Interworking bction TA Terminaladaptor TE Terminai equipment 4.5 Other a
33、bbreviations CSDN PSDN Circuit switched data network (public or private) packet switched data network (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 an X.21 Connection to provide the
34、OS1 Comiecton-mode Network Service (CONS) defined in CCTT Rec. X.213 I ISO/IEC 8348. The first configuration is shown in Figure la) where two X.25 DTES are directly mecd by one or more concatenated CSDNs, or by one or more ISDNs and one or two X.30 TAS (see Annex B). In this case each DTE operam the
35、 DTB/DTE mode of ISO/iEC 8208 (X.25 PLP) and IS0 7776 (X.25 LAPB). The meciion my be permanent or switched. The second configuration is shown in Figure lb) where an X.25 DTE access a PSDN. In this case the DTE operam the DTE/DCE mode of ISOWC 8208 (X.25 PLP) and IS0 7776 (X.25 LAPB). When the connec
36、tion is permanent this configuration is a regular X.25 scenario, while it relates to X.32 and X.3 1 when the connection is switched. -ll x.21 I FI+-FI I I x.21 bis a) Conjguratwn for DTE-TO-DTE operation x.21 1 x.21 bis U b) Conjguratwn for DTE-TO-PSDN operalion Figure 1 - Configurations 4 CCm Rec.
37、X.613 (1m E) ISO/IEC 10588 : 1993(E) X.21 or X.21 bis CCIT Rec. X.223 I IS0 8878 specifes the method for providing the OS1 Connection-mode Network Service (CONS) through the use of the X.25 PLP directly connected to another DTE or directly connected to a packet switched data network. When a circuit
38、switched (semi-permanent, hot line, or fuii 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 CC Rec. X.223 I IS0 8878 are necessary. These additional provisions for a DTE connected to a CSDN, or
39、 to an ISDN via a TA, are specified by this Recommendation I International Standard. 1 - 100590-92 The applicable protocol stack is given in Figure 2. The X.25 PLP is used to convey all elements of ali three phases of the OS1 CONS. CCIT Rec. X.223 I IS0 8878 applies with regard to the mapping of the
40、 CONS primitives and parameters to the elements of the X.25 PLP. However, in certain cases discussed in the clauses below, additionai provisions apply before these mappings can take place (e.g., to cover esablishment of a circuit switched connection) or in addition to these mappings (e.g., to cover
41、an unexpected diconnttion of the circuit switched connection). 4 I I This Recommendation I International Standard in conjunction with Recommendation X.223 I IS0 8878 3 ISO/IEC 8208 (X.25 PLP) IS0 7776 (X.25 LAPB) NOTE - These procedures are not used in the leased circuit case. At the physical layer
42、(and for signalling for a circuit switched connection), either X.21 or X.21 bis may be used. At the data link layer IS0 7776, as constrained by clause 7 of this Recommendation I International Standard, is used. At the network layer ISO/IEC 8208, as constrained by clause 8 of this Recommendation I In
43、ternational Standard, is used. The mapping of the elements of the CONS to the protocol and procedures of ISO/IEC 8208 shall be as required by CC Rec. X.223 I IS0 8878. The remaining clauses of this Recommendation I International Standard specify the provisions required in addition to these mappings.
44、 6 Control of underlying connections The following clauses cover the two types of underlying connections that can be operate : leased circuit connection, and circuit switched connection including direct cail. CClT Rec. X.613 (1992 E) 5 CCITT RECMN*X-bL3 92 = 48b259L 0575033 TTT Ismc 10588 : 1993(E)
45、6.1 Leased circuit conne!con x.21 oode Both the X.21 aud X.21 bis interfaces provide for a leased circuit connection. CONS Reason parameter No additional procedures are required. 6.2 Circuit Switched connection (including direct cail) Both the X.21 arid X.21 bis interfaces provide for a circuit swit
46、ched Connection. 6.2.1 Circuit switcbe conne!ction originated by DTE The foliowing additid procedure sha be used if a circuit switched Connection is not aiready estabished or if an additionai circuit switched Connection is needed to support the additional traffic. The mipt by layer 3 of an N-CONNECT
47、 request primitive sha first cause the X.21 or X.21 bis procedures to be used to estabiish the Connection. Following the successful estabiishment of this connecti on and the X.21 or X.21 bis procedm for enterhg the data transfer phase at layer 1, the Is0 7776 and ISOlIIX 8208 procedures sha apply as
48、 coostrained by clauses 7 and 8 of this Recommendation I Intemational Statidard. . Failure to esablish the Connection is indicated to the NS user by means of a N-DISCONNECT indication primitive with the originator parameter indicating “NS provider“ and the reason parameter as given m Table 1. Table
49、1 -Mapping of the X21 cail progress signals associated with clearing to the CONS Reasons 20 21 22 23 Connection rejection-NSAP unreachabldiransient Connection rejection-reason unspecinedltrans ient Connection rejection-reason unspeciedtransient Connection rejection-reason unspecifedtransient 41 42 43 44 45 46 47 48 49 Connection rejection-reason unspcciidpermanent Connection rejection-reason unspecifiedlpermanent Connection rejection-NSAP unreachal-anent connection rejection-mon unspecifiedlpermanen
