1、 STD.ITU-T RECMN X-225 AND 1-ENGL 1997 m Lib257L Ub43505 808 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATI ON SECTOR OF ITU . X.225 Amendment I (08/97) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Open System Interconnection - Connection-mode protocol specifi
2、cations Information technology - Open Systems Interconnection - Connection-oriented session protocol : Protocol specificat ion Amendment I : Efficiency enhancements ITU-T Recommendation X.225 - Amendment I (Previously CCIlT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM
3、 COMMUNICATION PUBLIC DATA NETWORKS Services and facilities Interfaces Transmission, signalling and switching Network aspects Maintenance Administrative arrangements OPEN SYSTEM INTERCONNECTION Model and notation Service definitions X. 1 -X. 199 X. 1-X. 19 X.20-X.49 X.50-X. 89 X.90-X. 149 X.150-X. 1
4、79 X.180-X. 199 X.200-X.299 X.200-X.209 X.210-X.219 Connection-mode protocol specifications X.220-X.229 Connectionless-mode protocol specifications PICS proformas Protocol Identification Security Protocols Layer Managed Objects Conformance testing INTERWORKING BETWEEN NETWORKS General Satellite data
5、 transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN.l) OS1 MANAGEMENT Systems Management framework and architecture Management Communication Service and Protocol Structu
6、re of Management Information Management functions SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING X.230-X.239 X.240-X.259 X.260-X.269 X.270-X.279 X.280-X.289 X.290-X.299 X.300-X.399 X .300-X.349 X.350-X.399 X.400-X.4
7、99 X.500-X.599 X.600-X.699 X .600-X . 629 X.630-X.649 X.650-X.679 X.680-X.699 X.700-X.799 X.700-X.709 X.710-X.719 X.720-X.729 X.730-X.799 X.800-X.849 X.850-X. 899 X.850-X.859 X.860-X. 879 X.880-X. 899 X.900-X.999 For further details, please refer to ITU-T List of Recommendations. - STD-ITU-T RECMN X
8、.225 AMD L-ENGL 1997 I 48b2571 UbY3507 bAO I INTERNATIONAL STANDARD 8327-1 ITU-T RECOMMENDATION X.225 INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - CONNECTION-ORIENTED SESSION PROTOCOL: PROTOCOL SPECIFICATION AMENDMENT 1 Efficiency enhancements Summary This amendment is one of a set of ame
9、ndments to the OS1 upper-layers standards produced to facilitate the interconnection of information processing systems in an open environment where efficiency of communications is paramount. Such efficiencies include: a) reduction in the overhead needed to encode control information for use in bandw
10、idth-limited environments (such as radio links) or processing-limited systems (such as switching systems); b) reduction in the delay to set up the association between the communicating applications so that data transfer can begin expeditiously; c) reduction in the support of unneeded functionality i
11、n certain environments where the communications requirements of the applications are limited. This amendment modifies the connection-oriented session protocol to support the “fast-associate” mechanism for establishing session and higher layer connections and also specifies the short-encoding and nul
12、l-encoding protocol mechanisms. The fast-associate mechanism allows the exchange of an identifier, and associated parameters that allow establishment of the session and higher-layer connections (and associations) with any specified set of options. The short-encoding option provides alternative, and
13、much smaller protocol control information for the most commonly occurring session protocol data units. The null-encoding option eliminates session protocol in the data transfer phase completely and can be selected when the session user has no requirements for orderly release of the session connectio
14、n and no session layer addressing .information needs to be exchanged. A special form of the fast-associate mechanism can be used indicating that the nuil-encoding will be used. The null-encoding, and the special form of fast-associate (involving the short-connect SPDU) is specified in Recommendation
15、 X.22YAmd. 2.1 Source The ITU-T Recommendation X.225, Amendment 1 was approved on the 9th of August 1997. The identical text is also published as ISO/IEC International Standard 8327-1. ITU-T Rec. X.225 (1995)/Amd.l (1997 E) 1 STD-ITU-T RECMN X.225 AND 1-ENGL 1777 B 4b257L UL435 517 FOREWORD ITU (Int
16、ernational Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Rec
17、ommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these to
18、pics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. . In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this R
19、ecommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve
20、 the use of a claimed Intellectual Propem Right. The IT takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by IT members or others outside of the Recommendation development process. As of the date of approval of this Recomme
21、ndation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.
22、 O ITU 1998 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 11 ITU-T Rec. X.225 (1995)/Amd.l (1997 E) 23) 24) 25) 26) 27) CONTENTS S
23、ubclause 2.1 . Subclause 2.3 . Subclause 3.4 . . . Subclause 4.2 . Subclause 5.2 . Subclause 5.4.2 Subclause 5.6 . Subclause 5.6.1 O Subclause 5.8 . Subclause 6.1.4 Subclause 6.3.3 Subclause 6.3.5 Subclause 6.3.7 Subclause 6.4.4 . Subclause 6.6.4 Subclause 7.1 . Subclause 7.1.1 . . Subclause 7.1.2 S
24、ubclause 7.4.1 Subclause 7.11 . Subclauses 7.38 through 7.41 . 7.38 SHORT CONNECT SPDU . 7.39 SHORT ACCEPT SPDU 7.40 SHORT CONNECT CONTINUE SPDU . 7.41 SHORT ACCEPT CONTINUE SPDU . 7.42 SHORT REFUSE SPDU 7.43 7.44 SHORT FINISH SPDU 7.45 SHORT DISCONNECT SPDU . . 7.46 SHORT DATA TRANSFER SPD . 7.47 S
25、HORT ABORT SPDU 7.48 Connection release when the null-encoding option is selec . 7.49 NULL SPDU . Subclause 8.2 . 8.2 SPDU structure (long form SPDUs) . Subclauses 8.2.1 through 8.2.8 . Subclauses 8.5 and 8.6 . 8.5 SPDU structure (short-form SPDUs) 8.6 Subclause 9.1.3 Subclause A.5.1 . Subclause A.5
26、.4.20 . SHORT REFUSE CONTINUE SPDU . . Short-form SPDU identifiers and associated parameter fields . ITU-T Rec . X.225 (1995)/Amd.l(1997 E) Page 1 1 1 1 2 2 2 3 3 5 6 6 6 6 7 7 7 7 7 8 8 8 9 11 11 12 13 13 14 15 15 16 16 16 16 17 17 17 18 24 24 24 . 111 ISOIEC 8327-1 : 1996/Amd.l : 1998 (E) INTERNAT
27、IONAL STANDARD ITU-T RECOMMENDATION INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - CONNECTION-ORIENTED SESSION PROTOCOL: PROTOCOL SPECIFICATION AMENDMENT 1 Efficiency enhancements . . 1) Subclause 2.1 Add the following reference by numerical order: - ITU-T Recommendation X.215 (1995)Amd.l (
28、1997) I ISO/IEC 8326:1996/Amd.1:1997, Information technology - Open Sysiems Interconnection - Session service definition - Amendment I: Eficiency enhancements. 2) Subclause 2.3 Add the following reference af2er Recommendation T. 62: - ITU-T Recommendation X.215 (1995)Addendum 1 (1995), Service defin
29、ition for Session Layer ejciency enhancement. 3) Subclause 3.4 Add the following definitions: 3.4.a 3.4.b null-encoding protocol option: An option of the session protocol, negotiated during connection establishment, that permits a data transfer phase with zero session protocol control information an
30、d without the ability to signal the orderly release of the session-connection. 3.4.c will contain the SPDU identifier). long-form SPDU: An SPDU that has the long-form structure defined in 8.2. parameter indication: A field in the low-order bits of the first octet of a short-form SPDU (the high-order
31、 bits 3.4.d short-connect protocol option: An option of the session protocol that permits an efficient negotiation, during connection establishment, of the fast associate mechanism (of which the null-encoding protocol defined in IT-T Rec. X.225 bis is a special case) by defining more compact encodin
32、gs for the connection establishment SPDUs than those defined in IT-T Rec. X.225 1 ISOIEC 8327-1. 3.4.e control information of some of the more commonly occurring Session SPDUs in the data transfer and release phases. 3.4.f names that begin with the word SHORT and abbreviations beginning with the let
33、ter S. short-encoding protocol option: An option of the session protocol that permits the use of smaller protocol short-form SPDU: An SPDU that has the short-form structure defined in 8.5. All short-form SPDUs have 4) Subclause 4.2 Add at the end of the abbreviations list: SI to negotiate the upper
34、layer context specification. 7) Subclause 5.6 Add a new subclause as follows: 5.6.2 bis No orderly release functional unit This functional unit removes the orderly release function from the kernel functional unit. 2 ITU-T Rec. X.225 (1995)/Amd.l (1997 E) - - STD-ITU-T RECNN X-225 AND 1-ENGL 1997 E 4
35、8b257L Ob43532 T48 ISOAEC 8327-1 : 199tdAmd.l : 1998 (E) 8) Subclause 5.6.10 Modi or compressible: a compressed form can be sent with the identifier, and the original form sent on a subsequent SPDU if the receiver is unable to reverse the compression. NOTE 1 - The Upper-layer context specification w
36、ill define the compression algorithm. The SPM will send the identifier for the Upper-layer context specification and any immediate or compressed parameters in the Connection summary parameter of a SHORT CONNECT SPDU. This SPDU may be sent on the User-data of a T-CONNECT request or on the normal tran
37、sport flow, using T-DATA. “he SHORT CONNECT SPDU shall only be sent on the T-CONNECT request if the size limitations of the Transport layer permit. How the SPM is made aware of these limits is a local matter. One of the following will then occur: . a) The responding SPM is able to reference the Uppe
38、r-layer context specification and expand any compressed parameters to their original form, and is thus able to reconstruct the CONNECT SPDU that would have been sent. If acceptable to the SPM, an S-CONNECT indication is issued to the SS-user, with no User-data parameter but with the User Summary par
39、ameter representing the semantic content of the User-data that would have been sent. If the SS-user replies with an S-CONNECT (accept) response, the SPM uses the Upper-layer context specification identified on the SHORT CONNECT SPDU to determine the identification of the Summary-response. Again this
40、 may have immediate and compressed parameters. The identification and any immediate or compressed parameters are sent in the Summary-response parameter of a SHORT ACCEPT SPDU, which also indicates that connection establishment is complete. The receipt of the SHORT ACCEPT SPDU at the initiator comple
41、tes the connection establishment. NOTE 2 -It is expected that the Upper-layer context identifier together with the short connect PCI will be designed to fit within the size limitation of the T-CONNECT User-data. The responding SPM is able to reference the Upper-layer context specification but there
42、are compressed parameters that the SPM cannot expand to their original form. The SPM asks for the uncompressed forms to be sent, by sending a SHORT ACCEPT SPDU indicating an incomplete connection establishment. The initiating SPM, on receiving the SHORT ACCEPT SPDU, sends a SHORT CONNECT CONTINUE SP
43、DU containing the uncompressed forms of the parameters. The responding SPM can now, if the received SPDUs are acceptable, issue an S-CONNECT indication with the semantic content of the missing User-data represented by the User Summary parameter. If the SS-user replies with an S-CONNECT (accept) resp
44、onse, the SPM uses the Upper-layer context specification identified on the SHORT CONNECT SPDU to determine the identification of the Summary-response and sends this, with any parameters in their uncompressed form on a SHORT ACCEPT CONTINUE SPDU. The responding SPM is unable to reference the Upper-la
45、yer context specification - the identifier is not recognized - and the SHORT CONNECT SPDU was received on an established connection. The SPM replies with SHORT REFUSE SPDU indicating the connection summary is unknown. On receiving the SHORT REFUSE SPDU, the initiating SPM switches to using the long-
46、form SPDUs for connection establishment, sending the original CONNECT SPDU including any User-data. The responding SPM is unable to reference the Upper-layer context specification - the identifier is not recognized - and the SHORT CONNECT SPDU was received on a T-CONNECT indication. The SPM ignores
47、it, and just completes the establishment of the transport connection. On receiving the T-CONNECT confirm with no SPDU in the User-data, the initiating SPM switches to using the long-form SPDUs for connection establishment, sending the original CONNECT SPDU. The responding SPM does not support the SH
48、ORT CONNECT SPDU and the SHORT CONNECT SPDU was received on an established connection. The SPM will perceive this as a protocol error and release the transport connection. b) c) d) e) 4 ITU-T Rec. X.225 (1995)/Arnd.l (1997 E) ISOEEC 8327-1 : 1996/Amd.l : 1998 (E) I) The responding SPM does not suppo
49、rt the SHORT CONNECT SPDU and the SHORT CONNECT SPDU was received on a T-CONNECT indication. The SPM ignores it, and just completes the establishment of the transport connection. On receiving the T-CONNECT confm with no SPDU in the User-data, the initiating SPM switches to using the long-form SPDUs for connection establishment, sending the original CONNECT SPDU. 5.8.9 The use of the null-encoding protocol option is negotiated between the peer SPMs at session-connection establishment. It shall only be offered by the initiating SPM if the ini
