1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU DATA NETWORKS AND OPEN SYSTEM CO MM UN ICATIONS OPEN SYSTEMS INTERCONNECTION - SERVICE DEFINITIONS x.211 (1 1/95) INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - PHYSICAL SERVICE DEFINITION ITU-T Reco
2、mmendation X.211 (Previously “CCITT Recommendation”) FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The IT Telecommunication Standardization Sector (IT-T) is a permanent organ of the ITU. Some 179 member countries, 84
3、 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 Recommendations by the Members of IW-T is covered by the procedure laid
4、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 for the following period. In some areas of information technology whi
5、ch fail within IT-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. The text of ITU-T Recommendation X.211 was approved on 21st of November 1995. The identical text is also published as ISO/IEC International Standard 10022. NOTE In this Recommendation, the e
6、xpression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITiJ 1996 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photoc
7、opying and microfilm, without permission in writing from the ITU. ITU-T RECMN*X.ZLL 95 48b2591 Ob32596 739 = - Subject area Recommendation Series PUBLIC DATA NETWORKS ITU-T X-SERIES RECOMMENDATIONS Services and Facilities Interfaces DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS - X.l-X.19 X.20-X.49 (
8、February 1994) Transmission, Signalling and Switching Network Aspects ORGANIZATION OF X-SERIES RECOMMENDATIONS X.50-X.89 X.90-X. 149 Maintenance Administrative Arrangements OPEN SYSTEMS INTERCONNECTION x. 150-x. 179 X.180-X.199 - Model and Notation Service Definitions Connection-mode Protocol Specif
9、ications Connectionless-mode Protocol Specifications PICS Profomas Protocol Identification Security Protocols - x.200-x.209 X.2 1 O-X.219 X.220-X.229 X.230-X.239 X.240-X.259 X.260-X.269 X.270-X.279 Layer Managed Objects Conformance Testing X.280-X.289 X.290-X.299 INTERWORKING BETWEEN NETWORKS Genera
10、l Mobile Data Transmission Systems X.300-X.349 X.350-X.369 Management MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS X.370-X.399 X.400-X.499 x.500-x.599 Networking Naming, Addressing and Registration Abstract Syntax Notation One (ASN.1) OS1 MANAGEMENT SECURITY X.600-X. 649 X.65
11、0-X.679 X.680-X.699 X.700-X. 799 X.800-X. 849 OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction Processing Remote Operations OPEN DISTRIBUTED PROCESSING X.850-X.859 X.860-X.879 X.880-X.899 X.900-X.999 CONTENTS Page 1 Scope 1 . 2 Normative references 1 2.1 Identical Recommendations I
12、International Standards 1 3 Definitions 1 3.1 Basic Reference Model definitions 1 3.2 Service convention definitions 2 . 4 Abbreviations . 2 5 Conventions 2 5.1 General conventions 2 5.2 Parameters . 2 5.3 PhC endpoint identification convention 3 6 Overview and general characteristics . 3 7 Features
13、 of the Physical Service . 3 7.2 Other aspects of the Physical Service include . 4 . 7.1 The Physical Service offers the following features to a PhS user 3 8 Classes of Physical Service 4 9 Model of the Physical Service 4 9.1 Model of the layer service 4 9.2 Model of a point-to-point PhC 5 9.3 Model
14、 of a relayed point-to-point PhC where the relay is controlled within the PhS Provider 9.4 Model of a relayed point-to-point PhC where the relay is controlled from the Network Layer . . 5 6 10 Quality of Physical Service 6 10.1 Definition of PhC QOS . 6 10.2 Determination of QOS values . 8 11 Sequen
15、ce of primitives . 8 1 1.2 Sequence of primitives at one PhC endpoint 8 1 1.1 Relation of primitives at the two PhC endpoints 8 12 PhC activation phase . 14 12.1 Function 14 12.2 Types of primitives and parameters 14 12.3 Sequence of primitives 14 13 PhC deactivation phase 14 13.1 Function 14 13.2 T
16、ypes of primitives and parameters 14 13.3 Sequence of primitives 14 14 Data transfer phase . 17 14.1 Function 17 14.2 Types of primitives and parameters 17 14.3 Sequence of primitives 17 ITU-T Rec. X.211(1995 E) i ITU-T RECMN*X.ZLL 95 W 4862593 Ob12548 503 Annex A . Internal structure of the Physica
17、l Layer A.l Introduction . A.3 Isochronous transmission Annex B - Operation of data link protocol using the half-duplex physical service B.l Inuoduction . B.2 Operation Annex C - Composite state transition diagram . C.1 Introduction . A.2 Classifications regarding multiplexing . 11 ITU-T Rec . X.211
18、(1995 E) Page i8 18 18 18 20 20 20 23 23 Summary This Recommendation I International Standard defines the set of capabilities, in terms of abstract service definition, provided by the Physical Layer to the Data Link Layer. For designers of Data Link Layer protocols, it provides a definition of the P
19、hysical service to allow design and implementation independent of details of the Physical Layer protocol. For designers of Physical Layer protocols, it defines the set of capabilities to be made available through the action of the protocol over the underlying physical media. Introduction This Recomm
20、endation I Intemational Standard is one of a set of Recommendations and International Standards produced to facilitate the interconnection of information processing systems. It is related to other Recommendations I International Standards in the set as defined by the Open Systems Interconnection (OS
21、I) Basic Reference Model (see ITU-T Rec. X.200 I ISO/IEC 7498-1). The OS1 Basic Reference Model subdivides the area of standardization for interconnection into a series of layers of specification, each of manageable size. This Recommendation I International Standard defines the service provided by t
22、he Physical Layer to the Data Link Layer at the boundary between the Physical and Data Link Layers of the OS1 Basic Reference Model, It provides for the designers of Data Link Protocols a definition of the Physical Service existing to support the Data Link Protocol and for the designers of Physical
23、Protocols a definition of the services to be made available through the action of the Physical Protocol over the underlying physical media, which are external to the OS1 Physical Layer. The relationship of the Physical Layer with the Data Link Layer is illustrated in Figure Intro. 1. NOTE - It is im
24、portant to distinguish the specialized use of the term ?Service? within the set of OS1 Recommendations I International Standards from its use elsewhere to describe the provision of a service by some organizations (i.e. the provision of a service by an Administration as defined in Recommendations of
25、the ITU-T). i Physical service A Physical layer -A Provides service Physical Prctocd - Figure Intro. 1 - Relationship of this Recommendation I International Standard to other OS1 Recommendations I International Standards . ITU-T Rec. X.211(1995 E) 111 ITU-T RECMN*X-ZLL 95 4862593 0632550 L6T INTERNA
26、TIONAL STANDARD ITU-T RECOMMENDATION INFORMATION TECHNOLOGY - OPEN SYSTEMS INTERCONNECTION - PHYSICAL SERVICE DEFINITION 1 Scope This Recommendation I International Standard defines the OS1 Physical Service in terms of: a) b) c) the primitive actions and events of the Service; the parameters associa
27、ted with each primitive action and event, and the form which they take; the interrelationship between, and the valid sequences of, these actions and events. The principal objective of this Recommendation I International Standard is to specify the characteristics of a conceptual Physical Service and
28、thus supplement the OS1 Basic Reference Model in guiding the development of Physical Layer protocols. This Recommendation I International Standard does not specify individual implementations or products nor does it constrain the implementation of entities and interfaces within an information process
29、ing system. There is no conformance of equipment to this Recommendation I International Standard. Instead, conformance is achieved through implementation of conforming OS1 Physical protocols that fulfil the Physical Service defined in this Recommendation I International Standard. 2 Normative referen
30、ces The following Recommendations and International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation I Intemational Standard. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject t
31、o revision, and parties to agreements based on this Recommendation I International Standard are encouraged to investigate the possibility of applying the most recent editions of the Recommendations and Standards listed below, Members of IEC and IS0 maintain registers of currently valid International
32、 Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid ITU-T Recommendations. 2.1 Identical Recommendations I International Standards - ITU-T Recommendation X.200 (1994) I ISO/IEC 7498-1 : 1994, Information technology - Open Systems Interconnection -
33、Basic Reference Model: The Basic Model. ITU-T Recommendation X.210 (1993) I ISO/IEC 10731:1994, Information technology - Open Systems Interconnection - Basic Reference Model: Conventions for the dejinition of OSI services. - 3 Definitions NOTE - Terms and definitions for Data communication and Open
34、Systems Interconnection Architecture are given in IS0 2382-9 and ISOAEC 2382-26. 3.1 Basic Reference Model definitions This Recommendation I International Standard is based on the concepts developed in the OS1 Basic Reference Model, ITU-T Rec. X.200 I ISOAEC 7498-1, and makes use of the following te
35、rms defined in it: a) Data circuit; b) Physical connection; c) Physical layer; ITU-T Rec. X.211 (1995 E) 1 d) Physical media; e) Physical service; f) Physical service access point; g) Physical service data unit. 3.2 Service convention definitions This Recommendation I International Standard also mak
36、es use of the following terms defined in the OS1 Service Conventions, ITU-T Rec. X.210 I ISOEC 10731, as they apply to the Physical Layer: a) Physical Service user; b) Physical Service provider; c) primitive; d) request; e) indication. 4 Abbreviations For the purposes of this Recommendation I Intern
37、ational Standard, the following abbreviations apply: OS1 Open Systems Interconnection Ph Physical PhC Physical Connection PhL Physical Layer PhFDU Physical Protocol Data Unit PhS Physical Service PhSAP Physical Service Access Point PhSDU Physical Service Data Unit QOS Quality of Service 5 Convention
38、s 5.1 General conventions This Recommendation 1 International Standard uses the descriptive conventions given in the OS1 Service Conventions, ITU-T Rec. X.210 I ISO/IEC 10731. The layer service model, service primitives, and time-sequence diagrams taken from those conventions are entirely abstract d
39、escriptions; they do not represent a specification for implementation. 5.2 Parameters Service primitives, used to represent service-userhervice-provider interactions see ITU-T Rec. X.210 I ISO/IEC 1073 1) may convey parameters that indicate information available in the useriprovider interaction. The
40、 parameters which apply to each group of Physical Service primitives are set out in Table 1 to Table 4 see clause 11 to clause 14). The tables also indicate the association of which parameters can be carried by each respective primitive. Some entries are further qualified by items in brackets. These
41、 may be: a) an indication that the parameter is conditional in some way: (C) indicates that the parameter is not present on the primitive for every connection; the parameter definition describes the conditions under which the parameter is present or absent; b) a parameter specific constraint: (=) in
42、dicates that the value supplied in an indication primitive is always identical to that supplied in a previous request primitive issued at the peer service access point; 2 ITU-T Rec. X.211(1995 E) ITU-T RECMNxX.211 95 48b2591 Ob12553 979 ISO/IEC 10022 : 1996 (E) C) an indication that some note applie
43、s to the entry: (Note x) indicates that the referenced note contains additional information pertaining to the parameter and its use. In any particular interface, not ail parameters need be explicitly stated. Some may be implicitly associated with the PhSAP at which the primitive is issued. 5.3 PhC e
44、ndpoint identification convention If at a PhSAP there is more than one PhC and distinction among them is needed by the PhS user, PhC endpoint identification must be provided. All primitives issued at such a PhSAP would be required to use this mechanism to identify PhCs. Such an implicit identificati
45、on is not described as a parameter of the service primitives in this Physical Service Definition. When the PhC traverses relays which are controlled through a separate PhC, this implicit identification mechanism must provide additionally for identification of these dependencies. 6 Overview and gener
46、al characteristics The Physical Service provides for the transparent transfer of data between PhS users. It makes invisible to the PhS users the way in which supporting communication resources are utilized to achieve this transfer. Service classes are defined to categorize the distinctions that are
47、visible to the PhS user. The PhS provides for PhCs between PhS users. Since connections cannot be established through the protocol at the Physical Layer but rather are configured when the service is created, the PhC, which is a logical concept, nevertheless must relate directly to the real physical
48、media paths provided to the Physical Layer. For this reason: There is no distinction between connection-mode and connectionless-mode at the Physical Layer. The service is independent of whether the higher layers operate in connection-mode or connectionless-mode. Each PhC is identified within the Phy
49、sical Layer. A PhC can only relate to a particular PhSAP (Le. a PhC implies a specific source PhSAP, and a specific destination PhSAP or group of PhSAPs if a multi-endpoint connection). a) b) c) The PhC may traverse Physical Layer relay, or intermediate systems when several physical media are used in tandem. Such relaying may be controlled through a management function exercised over a separate, but related, PhC, or may be controlled from the Network Layer, as specified in IT-T Rec. X.200 I ISO/EC 7498-1. 7.5.4.2, for the interconnection of data circ
