1、INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS OPEN SYSTEMS INTERCONNECTION - CON N ECTION-MODE PROTOCOL SPEC IF I CATI ON S X.225 (I 4 95) INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - CONNECTION-OR
2、IENTED SESSION PROTOCOL: PROTOCOL SPECIFICATION IT U -T Recommend at i on X. 22 5 (Previously “CCITT Recommendation”) FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (IT
3、U-T) is a permanent organ of the ITU. Some 179 member countries, 84 telecom operating entities, 145 scientific and industrial organizations and 38 international organizations participate in ITU-T which is the body which sets world telecommunications standards (Recommendations). The approval of Recom
4、mendations by the Members of ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, 1993). In addition, the World Telecommunication Standardization Conference (WTSC), which meets every four years, approves Recommendations submitted to it and establishes the study programme f
5、or the following period. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared onacollaborative basis with IS0 and IEC. The text of ITU-T Recommendation X.225 was approved on 21st of November 1995. The identical text is also published as ISOAE
6、C International Standard 8327-1. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1996 All rights reserved. No part of this publication may be reproduced or utilized in an
7、y form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T X-SERIES RECOMMENDATIONS Subject area DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Recommendation Series (February 1994) Transmission, Signalling and Switching Ne
8、twork Aspects ORGANIZATION OF X-SERIES RECOMMENDATIONS X.50-X.89 X.90-X. 149 Administrative Arrangements OPEN SYSTEMS INTERCONNECTION I PUBLIC DATA NETWORKS I X.180-X.199 I Services and Facilities I X. l-X. 19 Service Definitions Connection-mode Protocol Specifications 1 Interfaces I X.20-X.49 I X.2
9、 10-X.2 19 X.220-X.229 PICS Proformas Protocol Identification I Maintenance I X. 150-X. 179 I X.240-X.259 X.260-X.269 Layer Managed Objects Conformance Testing INTERWORKING BETWEEN NETWORKS I Model and Notation I X.200-X.209 I X.280-X.289 X.290-X.299 General Mobile Data Transmission Systems I Connec
10、tionless-mode Protocol Specifications I X.230-X.239 I X.300-X.349 X.350-X.369 MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS I Security Protocols I X.270-X.279 I X.400-X.499 X.500-X.599 Naming, Addressing and Registration Abstract Syntax Notation One (ASN. 1) X.650-X.679 X.680-
11、X.699 I Management I X.370-X.399 I OS1 APPLICATIONS Commitment, Concurrency and Recoverv X.850-X.859 I Networking I X.600-X.649 I I OS1 MANAGEMENT I X.700-X.799 I I SECURITY I X.800-X.849 I I Transaction Processing I X.860-X.879 I I Remote Operations I X.880-X.899 1 OPEN DISTRIBUTED PROCESSING X.900
12、-X.999 I STD-ITU-T RECMN X.225-ENGL 1995 YBb2571 Ob23bLB 5qO CONTENTS SECTION 1 . GENERAL Scope Normative references 2.1 Identical Recommendations I International Standards 2.2 Paired Recommendations I International Standards equivalent in technical content 2.3 Additional References . Definitions 3.
13、4 Session protocol definitions Abbreviations . 4.1 Data units 4.2 SPDU fields . 4.3 Timer variables 4.4 Miscellaneous 4.5 Local variables Overview of the session protocol . 5.1 Model of the session layer . 5.2 Services provided by the session layer 5.3 Services assumed from the transport layer 5.4 F
14、unctions of the session layer . 5.5 Protocol version numbers 5.6 Functional units . 5.7 Tokens . 5.9 Local variables 5.8 Negotiation SECTION 2 . SESSION PROTOCOL SPECIFICATION 6 Use of the transport service 6.1 Assignment of a session connection to the transport connection 6.2 Reuse of the transport
15、 connection . 6.3 Use of transport normal data . 6.4 Use of transport expedited data . 6.5 Flow control 6.6 Transport disconnection Elements of procedure related to SPDUs . 7.1 CONNECT SPDU . 7.2 OVERFLOW ACCEPT SPDU . 7.3 CONNECT DATA OVERFLOW SPDU 7.4 ACCEPT SPDU 7.5 REFUSE SPDU . 7.6 FINISH SPDU
16、. 7.7 DISCONNECT SPDU 7.8 NOT FINISHED SPDU 7.9 ABORT SPDU 7.10 ABORT ACCEPT SPDU 7 ITU-T Rec . X.225 (1995 E) Page 1 1 1 1 2 2 2 3 4 4 4 4 4 5 5 5 6 7 7 9 9 12 13 14 16 16 16 17 17 22 22 22 23 23 25 25 25 28 28 29 29 30 31 1 STD*ITU-T RECMN X-225-ENGL 1775 48b2571 Ob23b17 487 7.1 1 7.12 7.13 7.14 7
17、.15 7.16 7.17 7.18 7.19 7.20 7.2 1 7.22 7.23 DATA TRANSFER SPDU . 7.11.1 Content of DATA TRANSFER SPDU . 7.1 1.2 Sending the DATA TRANSFER SPDU . 7.1 1.3 Receiving the DATA TRANSFER SPDU EXPEDITED SPDU 7.12.1 Content of EXPEDITED SPDU 7.12.2 Sending the EXPEDITED SPDU 7.12.3 Receiving the EXPEDITED
18、SPDU . TYPED DATA SPDU . 7.13.1 Content of TYPED DATA SPDU . 7.13.2 Sending the TYPED DATA SPDU . 7.13.3 Receiving the TYPED DATA SPDU CAPABILITY DATA SPDU 7.14.1 Content of CAPABILITY DATA SPDU 7.14.2 Sending the CAPABILITY DATA SPDU 7.14.3 Receiving the CAPABILITY DATA SPDU . CAPABILITY DATA ACK S
19、PDU . 7.15.1 Content of CAPABILITY DATA ACK SPDU . 7.15.2 Sending the CAPABILITY DATA ACK SPDU . 7.15.3 Receiving the CAPABILITY DATA ACK SPDU GIVE TOKENS SPDU . 7.16.1 Content of GIVE TOKENS SPDU 7.16.2 Sending the GIVE TOKENS SPDU 7.16.3 Receiving the GIVE TOKENS SPDU PLEASE TOKENS SPDU 7.17.1 Con
20、tent of PLEASE TOKENS SPDU 7.17.2 Sending the PLEASE TOKENS SPDU 7.17.3 Receiving the PLEASE TOKENS SPDU . GIVE TOKENS CONFIRM SPDU 7.18.1 Content of GIVE TOKENS CONFIRM SPDU . 7.18.2 Sending the GIVE TOKENS CONFIRM SPDU . 7.18.3 Receiving the GIVE TOKENS CONFIRM SPDU . GIVE TOKENS ACK SPDU 7.19.1 C
21、ontent of GIVE TOKENS ACK SPDU 7.19.2 Sending the GIVE TOKENS ACK SPDU 7.19.3 Receiving the GIVE TOKENS ACK SPDU . MINOR SYNC POINT SPDU 7.20.1 Content of MINOR SYNC POINT SPDU 7.20.2 Sending the MINOR SYNC POINT SPDU 7.20.3 Receiving the MINOR SYNC POINT SPDU . MINOR SYNC ACK SPDU . 7.2 1.1 Content
22、 of MINOR SYNC ACK SPDU 7.21.2 Sending the MINOR SYNC ACK SPDU 7.21.3 Receiving the MINOR SYNC ACK SPDU . MAJOR SYNC POINT SPDU 7.22.1 Content of MAJOR SYNC POINT SPDU 7.22.2 Sending the MAJOR SYNC POINT SPDU 7.22.3 Receiving the MAJOR SYNC POINT SPDU . MAJOR SYNC ACK SPDU . 7.23.1 Content of MAJOR
23、SYNC ACK SPDU . 7.23.2 Sending the MAJOR SYNC ACK SPDU . 7.23.3 Receiving the MAJOR SYNC ACK SPDU Page 32 32 32 32 33 33 33 33 33 33 34 34 34 34 34 34 34 34 34 35 35 35 35 35 35 35 36 36 36 36 36 36 36 36 36 36 36 37 37 37 37 37 37 38 38 38 38 38 39 39 39 39 11 ITU-T Rec . X.225 (1995 E) STD-ITU-T R
24、ECMN X-225-ENGL 1775 48b259L Db23b2D IT7 7.24 7.25 7.26 7.27 7.28 7.29 7.30 7.3 1 7.32 7.33 RESYNCHRONIZE SPDU . 7.24.1 Content of RESYNCHRONIZE SPDU . 7.24.2 Sendingreceiving the RESYNCHRONIZE SPDU without symmetric synchronization . 7.24.2.1 Sending the RESYNCHRONIZE SPDU without symmetric synchro
25、nization 7.24.2.2 Receiving the RESYNCHRONIZE SPDU without symmetric synchronization . 7.24.2.3 Resynchronization contention without symmetric synchronization Sendingreceiving the RESYNCHRONIZE SPDU with symmetric synchronization . 7.24.3.1 7.24.3.2 Receiving the RESYNCHRONIZE SPDU with symmetric sy
26、nchronization . 7.24.3.3 Resynchronization contention with symmetric synchronization . RESYNCHRONIZE ACK SPDU . 7.25.1 Content of RESYNCHRONIZE ACK SPDU . 7.25.2 Sendingheceiving the RESYNCHRONIZE ACK SPDU without symmetric synchronization . 7.25.2.1 Sending the RESYNCHRONIZE ACK SPDU without symmet
27、ric synchronization . 7.25.2.2 Receiving the RESYNCHRONIZE ACK SPDU without symmetric synchronization . 7.25.3 Sendingheceiving the RESYNCHRONIZE ACK SPDU with symmetric synchronization . 7.25.3.1 Sending the RESYNCHRONIZE ACIS SPDU with symmetric 7.25.3.2 Receiving the RESYNCHRONIZE ACK SPDU with s
28、ymmetric PREPARE SPDU 7.26.1 Content of PREPARE SPDU 7.26.2 Sending the PREPARE SPDU 7.26.3 Receiving the PREPARE SPDU . EXCEPTION REPORT SPDU . 7.27.1 Content of EXCEPTION REPORT SPDU . 7.27.2 Sending the EXCEPTION REPORT SPDU . 7.27.3 EXCEPTION DATA SPDU . 7.28.1 Content of EXCEPTION DATA SPDU 7.2
29、8.2 Sending the EXCEPTION DATA SPDU 7.28.3 Receiving the EXCEPTION DATA SPDU . ACTIVITY START SPDU . 7.29.1 Content of ACTIVITY START SPDU . 7.29.2 Sending the ACTIVITY START SPDU . 7.29.3 Receiving the ACTIVITY START SPDU ACTIVITY RESUME SPDU 7.30.1 Content of ACTIVITY RESUME SPDU 7.30.2 Sending th
30、e ACTIVITY RESUME SPDU 7.30.3 Receiving the ACTIVITY RESUME SPDU . ACTIVITY INTERRUPT SPDU 7.3 1.1 Content of ACTIVITY INTERRUPT SPDU 7.3 1.2 Sending the ACTIVITY INTERRUPT SPDU 7.3 1.3 Receiving the ACTIVITY INTERRUPT SPDU . ACTIVITY INTERRUPT ACK SPDU . 7.32.1 Content of ACTIVITY INTERRUPT ACK SPD
31、U . 7.32.2 Sending the ACTIVITY INTERRUPT ACK SPDU . 7.32.3 Receiving the ACTIVITY INTERRUPT ACK SPDU ACTIVITY DISCARD SPDU 7.33.1 Content of ACTIVITY DISCARD SPDU . 7.33.2 7.33.3 7.24.3 Sending the RESYNCHRONIZE SPDU with symmetric synchronization synchronization . synchronization . Receiving the E
32、XCEPTION REPORT SPDU Sending the ACTIVITY DISCARD SPDU . Receiving the ACTIVITY DISCARD SPDU Page 39 40 40 40 41 41 42 42 42 43 44 44 45 45 45 45 45 45 46 46 46 46 47 47 47 47 48 48 48 48 48 49 49 49 49 49 49 50 50 50 50 50 50 50 51 51 51 51 51 51 . ITU-T Rec . X.225 (1995 E) 111 STDmITU-T RECMN X-2
33、25-ENGL 1995 48b2591 Ob23b21 035 7.34 ACTIVITY DISCARD ACK SPDU . 7.34.1 Content of ACTIVITY DISCARD ACK SPDU . 7.34.2 Sending the ACTIVITY DISCARD ACK SPDU . 7.34.3 Receiving the ACTIVITY DISCARD ACK SPDU ACTIVITY END SPDU 7.3 5.1 Content of ACTIVITY END SPDU 7.35.2 7.35.3 ACTIVITY END ACK SPDU 7.3
34、6.1 7.36.2 Sending the ACTIVITY END ACK SPDU 7.36.3 Receiving the ACTIVITY END ACK SPDU . Additional Elements of Procedure for Segmented SSDUs . 7.37.1 Content of the SPDU . 7.37.2 Sending the SPDU . 7.37.3 Receiving the SPDU Structure and encoding of SPDUs 8.1 TSDU structure . 8.2 SPDU structure 8.
35、2.1 SPDUs 8.2.2 PGI units 8.2.3 PI units 8.2.4 Identifier fields 8.2.5 Length indicator field 8.2.6 Parameter fields . 8.2.7 Parameter values . 8.2.8 User information fields SPDU identifiers and associated parameter fields . 7.3 5 Sending the ACTIVITY END SPDU Receiving the ACTIVITY END SPDU . Conte
36、nt of ACTIVITY END ACK SPDU 7.36 7.37 8 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.3.8 8.3.9 8.3.10 8.3.1 1 8.3.12 8.3.13 8.3.14 8.3.15 8.3.16 8.3.17 8.3.18 8.3.19 8.3.20 8.3.21 8.3.22 8.3.23 8.3.24 8.3.25 8.3.26 8.3.27 CONNECT (CN) SPDU OVERFLOW ACCEPT (OA) SPDU CONNECT DATA OVERFLOW (CDO) SPD
37、U ACCEPT (AC) SPDU . REFUSE (RF) SPDU FINISH (FN) SPDU DISCONNECT (DN) SPDU . NOT FINISHED (NF) SPDU ABORT (AB) SPDU . DATA TRANSFER (DT) SPDU EXPEDITED (EX) SPDU . TYPED DATA (TD) SPDU ABORT ACCEPT (AA) SPDU . CAPABILITY DATA (CD) SPDU . CAPABILITY DATA ACK (CDA) SPDU . PLEASE TOKENS (PT) SPDU GIVE
38、 TOKENS CONFIRM (GTC) SPDU . GIVE TOKENS ACK (GTA) SPDU MINOR SYNC POINT (MIP) SPDU . MINOR SYNC ACK (MIA) SPDU MAJOR SYNC ACK (MAA) SPDU RESYNCHRONIZE (RS) SPDU RESYNCHRONIZE ACK (RA) SPDU GIVE TOKENS (GT) SPDU MAJOR SYNC POINT (MAP) SPDU PREPARE (PR) SPDU EXCEPTION REPORT (ER) SPDU . Page 51 52 52
39、 52 52 52 52 52 53 53 53 53 53 54 54 54 55 55 56 57 57 57 57 57 57 58 58 58 58 62 62 63 66 67 68 68 69 70 70 70 71 71 72 72 73 74 74 74 75 75 76 77 78 79 80 iv ITU-T Rec . X.225 (1995 E) STD*ITU-T RECMN 1995 LlBb259L Ob23b22 T7L 8.3.28 8.3.29 8.3.30 8.3.3 1 8.3.32 8.3.33 8.3.34 8.3.35 8.3.36 Additio
40、nal encoding rules for segmented SSDUs . 8.4.1 8.4.2 Subsequent SPDUs in a sequence . EXCEPTION DATA (ED) SPDU . ACTIVITY START (AS) SPDU . ACTIVITY RESUME (AR) SPDU . ACTIVITY INTERRUPT (AI) SPDU ACTIVITY INTERRUPT ACK (AIA) SPDU ACTIVITY DISCARD (AD) SPDU . ACTIVITY DISCARD ACK (ADA) SPDU . ACTIVI
41、TY END (AE) SPDU . ACTIVITY END ACK (AEA) SPDU . First SPDU in sequence . 8.4 Page 80 81 82 83 84 84 85 85 86 86 86 86 SECTION 3 . CONFORMANCE 88 9 Conformance to this Recommendation I International Standard 88 9.1 Static conformance requirements 88 9.2 Dynamic conformance requirements 89 9.3 Protoc
42、ol Implementation Conformance Statement . 89 Annex A . State tables A.l General A.2 Notation for state tables . A.3 Conventions for entries in state tables . A.4 Actions to be taken by the SPM A.4.1 Invalid intersections A.4.2 Valid intersections . A.4.3 Receipt of SPDUs Definitions of sets and vari
43、ables . A.5.1 Functional units . A.5.2 Tokens . A.5.3 SET oftokens A.5.4 Variables . A.5.4.1 TEXP . A.5.4.2 Vact . A.5.4.3 Vnextact A.5.4.4 Vrsp and Vrspnb . A.5.4.5 Vrsps, Vrspr, Vspnbs, and Vrspnbr . A.5.4.6 SPMwinner A.5.4.7 Vtca . A.5.4.8 Vrr A.5.4.9 Vcoll A.5.4.10 Vdnr A.5.4.11 V(A) A.5.4.12 V(
44、M) A.5.4.13 V(R) A.5.4.15 V(Ado) A.5.4.16 V(Adi) . A.5.4.17 V(As), V(Ar) . A.5.4.18 V(Ms), V(Mr) A.5.4.19 V(Rs), V(k) . A.5.4.20 Discard-rcv-flow - Discard-snd-flow . A.5 A.5.4.14 Vsc 90 90 90 90 91 91 91 91 92 92 93 94 94 94 94 94 95 95 95 96 96 97 97 97 97 97 97 97 97 97 98 98 98 Annex B . PGIs an
45、d PIS reserved for use by Recommendation T.62 . Annex C . Relationship to Recommendation T.62 encoding Annex D . Differences between Protocol Version 1 and Protocol Version 2 . 162 163 166 ITU-T Rec . X.225 (1995 E) V Summary This Recommendation I International Standard specifies a protocol which is
46、 used to provide the connection-mode session service specified in Recommendation X.215. vi ITU-T Rec. X.225 (1995 E) - - - STDmITU-T RECMN X.225-ENGL 1995 48b2591 Ob23b24 844 Introduction This Recommendation I Intemational Standard is one of a set of Recommendations I International Standards produce
47、d to facilitate the interconnection of computer systems. The set of Recommendations 1 International Standards covers the services and protocols required to achieve such interconnection. This Recommendation I International Standard is positioned with respect to other related Recommendations I Interna
48、tional Standards by the layers defined in the Reference Model for Open Systems Interconnection (see ITU-T Rec. X.200 I ISO/IEC 7498-1). It is most closely related to and lies within the field of application of the Session Service Definition (see IT-T Rec. X.215 I ISOIIEC 8326). It also uses and refe
49、rences the Transport Service Definition (see ITU-T Rec. X.214 I ISO/IEC 8072), whose provisions it assumes in order to accomplish the aims of the session protocol. The interrelationship of these Recommendations I International Standards is depicted in Figure Intro. 1. This Recommendation I International Standard specifies a single protocol with a common encoding. It is intended that the session protocol should be general enough to cater for the total range of session service users without restricting future extensions. The protocol is structured so that subsets of protoc
