1、 ITU-T RECNN*Xm2L2 95 4862593 Ob32574 bT3 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA NETWORKS AND OPEN SYSTEM COMM UNICATIONS SERVICE DEFINITIONS OPEN SYSTEMS INTERCONNECTION - x.212 (1 1/95) INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTIO
2、N - DATA LINK SERVICE DEFINITION ITU-T Recommendation X.212 (Previously “CCITT Recommendation”) - ITU-T RECMN*X.212 75 4862571 Ob12575 53T FOREWORD IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standa
3、rdization Sector (ITU-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 IT-T which is the body which sets world telecommunications standards (Recommendations). Th
4、e approval of Recommendations 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 th
5、e study programme for the following period. In some areas of information technology which fail within IT-Ts purview, the necessary standards are prepared on acollaborative basis with IS0 and EC. The text of IT-T Recommendation X.212 was approved on 21st of November 1995. The identical text is also p
6、ublished as ISO/IEC International Standard 8886. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O IT 1996 All rights reserved. No part of this publication may be reproduced or
7、 utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the IT. - ITU-T RECMN*X.212 95 W Y862591 Ob1257b 476 - Subject area PUBLIC DATA NETWORKS ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIO
8、NS Recommendation Series (February 1994) Services and Facilities Interfaces ORGANIZATION OF X-SERIES RECOMMENDATIONS X. 1 -X. 19 X.20-X.49 Transmission, Signalling and Switching Network Aspects Maintenance X.50-X.89 X.90-X. 149 X. 150-X. 179 Administrative Arrangements OPEN SYSTEMS INTERCONNECTION X
9、.180-x. 199 I Model and Notation I x.200-x.209 I Service Definitions Connection-mode Protocol Specifications X.210-X.219 X.220-X.229 Connectionless-moe Protocol Specifications PICS Profonas X.230-X.239 X.240-X.259 I Layer Managed Objects I X.280-X.289 I Protocol Identification Securitv Protocols X.2
10、60-X.269 X.270-X.279 Conformance Testing INTERWORKING BETWEEN NETWORKS X.290-X.299 General Mobile Data Transmission Systems x.300-x.349 X.350-X.369 Management MESSAGE HANDLING SYSTEMS I Commitment, Concurrency and Recovery I X.850-X.859 I X.370-X.399 X.400-X.499 X. 500-X. 599 OS1 NETWORKING AND SYST
11、EM ASPECTS Networking X .600-X.649 Naming, Addressing and Registration Abstract Syntax Notation One (ASN. 1) OS1 MANAGEMENT SECURITY OS1 APPLICATIONS X.650-X.679 X.680-X.699 x.700-x.799 X.800-X.849 Transaction Processing Remote Operations X.860-X.879 X.880-X. 899 I OPEN DISTRIBUTED PROCESSING X.900-
12、X.999 ITU-T RECMN*X.232 95 4862593 Ob32577 302 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 CONTENTS Scope Normative references . 2.1 Identical Recommendations I International Standards Definitions 3.1 OS1 Reference Model definitions . 3.2 Service Conventions definitions . 3.3 Data Link Service definit
13、ions . Abbreviations . Conventions 5.1 General conventions 5.2 Parameters . Overview of the Data Link Service Classes and types of Data Link Service . Features of the connection-mode Data Link Service . Model of the connection-mode Data Link Service 9.1 DLC Endpoint Connection Identification . 9.2 M
14、odel of a Data-link-connection Quality of connection-mode Data Link Service . Determination of QOS for Connection-mode Service Definition of connection-mode QOS parameters 10.1 10.2 Sequence of primitives . 11.1 Concepts used to define the connection-mode Data Link Service 11.2 Connection establishm
15、ent phase 12.1 Function 12.2 Constraints of Sequence of Primitives Types of primitives and parameters 12.3 Sequence of primitives Connection release phase . Types of primitive and parameters Sequence of primitives when releasing an established DLC 13.1 Function 13.2 13.3 13.4 Sequence of primitives
16、in a DLS user rejection of DLC establishment attempt . 13.5 Sequence of primitives in a DLS provider rejection of a DLC establishment attempt . 13.6 Sequence of primitives in a DLS user abort of a DLC establishment attempt Data transfer phase . 14.1 Data transfer 14.2 Reset service . Features of the
17、 Connectionless-mode Data Link Service . Model of the Connectionless-mode Data Link Service 16.1 Model of a data-link-connectionless-mode data transmission Quality of Connectionless-mode Service . 17.1 Determination of QOS for Connectionless-mode Service 17.2 Definition of connectionless-mode QOS pa
18、rameters ITU-T Rec . X.212 (1995 E) Page 1 1 1 1 1 2 2 2 2 2 3 3 3 4 4 4 4 7 7 8 10 10 10 12 12 13 14 14 14 15 16 17 17 17 18 18 19 21 21 22 22 23 23 1 - ITU-T RECflN+X.212 95 m 486259JI CI612538 249 = Page 18 24 19 Data transfer . 25 19.1 Function 25 19.2 Types of primitives and parameters 25 19.3
19、Sequence of primitives 26 Sequence of connectionless-mode primitives at one DLSAP _ . 11 ITU-T Rec. X.212 (1995 E) Summary This Recommendation I International Standard defines the set of capabilities, in terms of an abstract service definition, provided by the Data Link Layer to the Network Layer. F
20、or designers of Network Layer protocols, it provides a definition of the Data Link service to allow design and implementation independent of details of the Data Link Layer protocol. For designers of Data Link Layer protocols, it defines the set of capabilities to be made available through the action
21、 of the protocol. Introduction This Recommendation I International Standard is one of a set of Recommendations I International Standards produced to facilitate the interconnection of information processing systems. It is related to other Recommendations I International Standards in the set as define
22、d by IT-T Rec. X.200 I ISO/IEC 7498-1,OSI Reference Model - The Basic Model. The reference model described by ITU-T Rec. X.200 I ISO/IEC 7498-1 subdivides the area of standardization for Open Systems Interconnection (OSI) into a series of layers of specification, each of a manageable size. This Reco
23、mmendation I International Standard defines the services provided by the Data Link Layer to the Network Layer at the boundary between the Data Link and Network Layers of the OS1 Reference Model. It provides for the designers of network protocols a definition of the Data Link Service existing to supp
24、ort the network protocol and for the designers of Data Link Protocols a definition of the services to be made available through the action of the Data Link Protocol over the underlying service. The relationship is illustrated in Figure Intro. 1. Throughout the set of OS1 Recommendations I Internatio
25、nal Standards, the term “service” refers to the abstract capability provided by one layer of the OS1 Reference Model to the layer immediately above. Thus, the Data Link Service defined in this Recommendation I Intemational Standard is a conceptual architectural service, independent of administrative
26、 divisions. Data Link Layer Network Protocol Data Link Protocol TO721 7695/d01 Figure Intro. 1 - Relationship of this Recommendation I International Standard to other OS1 Recommendations I International Standards . ITU-T Rec. X.212 (1995 E) 111 - - ITU-T RECMNUX.212 95 m 4862593 Ob32580 9T7 m ITU-T
27、RECMN*X=ZLZ 95 4862593 Ob32583 833 M ISO/IEC 8886 : 1996 (E) INTERNATIONAL STANDARD ITU-T RECOMMENDATION INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - DATA LINK SERVICE DEFINITION 1 Scope This Recommendation I International Standard defines the OS1 Data Link Service in terms of a) b) c) th
28、e primitive actions and events of the service; the parameters associated with each primitive action and event, and the form that they take; and the interrelationship between, and the valid sequences of these actions and events. The principal objective of this Recommendation I International Standard
29、is to specify the characteristics of a conceptual Data Link Service and thus, supplement the OS1 Reference Model in guiding the development of Data Link Protocols. This Recommendation I International Standard does not specify individual implementation or products, nor does it constrain the implement
30、ation of Data Link entities and interfaces within an information processing system. There is no conformance of equipment to this Data Link Service Definition Recommendation I International Standard. Instead, conformance is achieved through implementation of conforming Data Link Protocols that fulfil
31、 the Data Link Service defined in this Recommendation I International Standard. 2 Normative references The following Recommendations and International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation I International Standard. At the tim
32、e of publication, the editions indicated were valid. All Recommendations and International 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 most recent edition of the Recom
33、mendations and Standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. The Telecommunication Standardization Bureau maintains a list of currently valid ITLJ-T Recommendations. 2.1 Identical Recommendations I International Standards - IT-T Recomme
34、ndation X.200 (1994) I ISOAEC 7498-1:1994, Information technology - Open Systems Interconnection - Basic Reference Model: The Basic Model. ITU-T Recommendation X.210 (1993) I ISOAEC 10731: 1994, Information technology - Open Systems Interconnection - Basic Reference Model: Conventions for the defini
35、tion of OS1 services. - PART 1 - GENERAL 3 Definitions 3.1 OS1 Reference Model definitions This Recommendation I International Standard is based on the concepts developed and makes use of the following terms defined in ITU-T Rec. X.200 I ISO/IEC 7498-1: a) Data link entity; b) Data Link Layer; c) Da
36、ta Link Service; d) Data-link-service-access-point; ITU-T Rec. X.212 (1995 E) 1 ITU-T RECMN*X*2LZ 95 4862591 Ob12582 77T H ISO/IEC 8886 : 1996 (E) e) Data-link-service-access-point-address; f) Data-link-service-data-unit; g) Reset. 3.2 Service Conventions definitions This Recommendation I Internatio
37、nal Standard makes use of the following terms defined in IT-T Rec. X.210 I ISO/IEC 10731, as they apply to the Data Link Layer: a) Data Link Service Users; b) Data Link Service Provider; c) Primitive; d) Request; e) Indication; f) Response; g) Confirm. 3.3 Data Link Service definitions This Recommen
38、dation I International Standard makes use of the following terms: a) data-link-connection An association established by a Data Link Layer between two or more Data Link Service Users for the transfer of data, which provides explicit identification of a set of Data Link data transmissions and agreemen
39、t concerning the Data Link data transmission services to be provided for the set. NOTE -This definition clarifies the definition given in ITU-T Rec. X.200 I ISO/IEC 7498- 1. b) data-link-connection-mode data transmission The transmission of a Data-link-service-data-unit within the context of a Data-
40、link-connection that has been previously established. c) data-link-connectionless-mode data transmission The transmission of a Data-link-service-data-unit not in the context of a Data-link-connection and not required to maintain any logical relationship among multiple invocations. 4 Abbreviations Fo
41、r this purposes of this Recommendation I International Standard, the following abbreviations apply: DL Data Link DLC Data-link-connection DLL Data Link Layer DLS Data Link Service DLSAP Data-link-service-access-point DLSDU Data-link-service-data-unit os1 Open Systems Interconnection QOS Quality of S
42、ervice 5 Conventions 5.1 General conventions This Recommendation I International Standard uses the descriptive conventions given in ITU-T Rec. X.210 I ISO/IEC 10731. The service model, service primitives, and time-sequence diagrams used are entirely abstract descriptions; they do not represent a spe
43、cification for implementation. 2 ITU-T Rec. X.212 (1995 E) ITU-T RECMN*X.232 95 W 48b2573 Ob32583 bob ISO/IEC 8886 : 1996 (E) 5.2 Parameters Service primitives, used to represent service user/service provider interactions (see ITU-T Rec. X.210 I ISO/IEC 1073 i), convey parameters which indicate info
44、rmation available in the user/provider interaction. The parameters which apply to each group of Data Link Service primitives are set out in tables in clauses 12 to 14 and 19. Each “X” in the tables indicates that the primitive labelling the column in which it falls may cany the parameter labelling t
45、he row in which it falls. Some entries are further qualified by items in brackets. These may be: a) A parameter specific constraint: (=) indicates that the value supplied in an indication or confirm primitive is always identical to that supplied in a previous request or response primitive issued at
46、the peer service-access-point Indication that some Note applies to the entry: (See Note X) indicates that the referenced Note contains additional information pertaining to the parameter and its use. In any particular interface, not all parameters need be explicitly stated. Some may be implicitly ass
47、ociated with the DLSAP at which the primitive is issued. b) 6 Overview of the Data Link Service The DLS provides for the transparent and reliable transfer of data between DLS users. It makes invisible to these DLS users the way in which supporting communications resources are utilized to achieve thi
48、s transfer. In particular, the DLS provides for the following: Independence of undedying Physical Layer - The DLS relieves DLS users from all concerns regarding which configuration is available (e.g. point-to-point connection) or which physical facilities are used (e.g. half-duplex transmission). Tr
49、ansparency of transferred information - The DLS provides for the transparent transfer of DLS user- data. It does not restrict the content, format or coding of the information, nor does it ever need to interpret its structure or meaning. Reliable transfer of data - The DLS relieves the DLS user from loss, insertion, corruption or, if requested, misordering of data which may occur. In some cases of unrecoverable errors in the Data Link Layer, duplication or loss of DLSDUs may occur. NOTE 1 - Detection of duplicate or lost DLSDUs may be p
