1、I NTERNATIONAL STANDARD ISO/IEC 11575 First edition 1995-07-01 (Reaffirmed 2004) Information technology - Telecommunications and inform at ion exchange between systems - Protocol mappings for the OS1 Data Link service Technologies de /information - Tklecommunications et echange dinformation entre sy
2、stemes - Applications du protocote au service de liaison de donnkes OS/ National Standard of Canada CAN/CSA-ISO/IEC-l1575-96 International Standard ISO/IEC 11575 : 1995 has been adopted, without modification, as CAN/CSA-ISO/IEC-11575-96, which has been approved as a National Standard of Canada by th
3、e Standards Council of Canada. April 1996 Reference number lSO/lEC 11 575:1995(E) ISOiIEC 11575: 1995(E) Contents Page Foreword _II 1 Scope 2 Normative References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Definitions 4 Abbreviations I,11 5 Conformance 6 Gene
4、ral principles of the protocol mappings . . . . . . . . . . . . . . . . . . . . . . . . 7 Protocol mapping for ISOiIEC 7776 single link procedures . . . . . . . . . , . . 8 Protocol mapping for HDLC Unbalanced operation Nomial response mode Class(UNC) . 9 Protocol mappings for LLC Types 1 and 2 . .
5、. . . . . . . . . . . . - . . . . . . . . . . 10 Protocol mappings for HDLC connectionlessmode classes of procedure . .-. 111 1 1 2 2 3 3 6 8 11 15 0 ISO/IEC 1995 AI1 rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, e
6、lectronic r mechanical, including photocopying and microfilm, without permission in writing from the publisher. PSO/IEC Copyright Office Case postale 56 CH-1211 Genhe 20 Switzerland 11 0 ISOnEC ISO/IEC 11575:1995(E) Foreword IS0 (the International Organization for Standardization) and IEC (the Inter
7、national Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of IS0 or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fi
8、elds of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non- governmental, in liaison with IS0 and IEC, also take part in the work. In the field of information technology, IS0 and IEC have established
9、a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75 % of the national bodies casting a vote. International Standard I
10、SO/IEC 11575 was prepared by Joint Technical Committee ISOAEC JTC 1, Information technology. . 111 INTERNATIONAL STANDARD ISOflEC ISOlIEC 11575 : 1995 (E) Information technology - Telecommunications and information exchange between systems - Protocol mappings for the OS1 Data Link service 1 Scope Th
11、is International Standard specifies general principles for the mappings between the OS1 Data Link service (ISO/IEC 8886), both connection-mode (CO-DLS) and connectionless-mode (CL-DLS), and standard Data Link protocols, as follows: M 1: M2: M3: M4: CL-DLS - LLC Type 1 (ISO/IEC 8802-2) M5: M6: CO-DLS
12、 - HDLC X.25 LAPB-compatible DTE procedures, single link procedures (ISO/IEC 7776) CO-DLS - HDLC Unbalnnced operation Noi-m;d response niode Class. UNC (ISO/iEC 3309, ISO/IEC 4335 and ISOAEC 7809) CO-DLS - Logical link control (LLC) Type 2 (ISO/IEC 8802-2) CL-DLS - HDLC Bnlnnced operation Coinection
13、less-nioe Class, BCC (ISOIIEC 3309, ISO/IEC 4335 and ISO/IEC 7809) CL-DLS - HDLC Unbalanced operation Connectionless-mode Class. UCC (ISO/IEC 3309, ISO/rEC 4335 and ISOflEC 7809) This International Standard specifies the detailed mappings M1. M2, M5 and MG; it also specifies the nuin features of the
14、 mappings M3 and M4. This International Standard does not specify individual implementations or products, nor does it constrain the implementation of Data Link entities and interfaces within an information processing system. NOTES 1 The above designations M1 to M6 for the mappings are used elsewhere
15、 in this 1ntern:itionnl Standard. 2 The possibility of adding further mappings to the above list in the future is not precluded (for example, to cover Frame Relay protocols). 2 Normative references The following standards contain provisions which, through reference in this text, constitute provision
16、s of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards l
17、isted below. Members of IEC and IS0 maintain registers of currently valid International Standards. ISODEC 3309: 1993, Iifotniatinu teciirrolngy - Telccoimrtiicoiiolls aiid iq%i-niarinn exchange between systems - High-/eve1 data link control (HDLC) procedures - Fi-orwe stiw:ture. ITU-T Recommendation
18、 X.200 (1 994) 1 ISO/IEC 7498-1 : 1994, Iifiiri?rufioii tecli,rolngy - Ojieii Sysfcnzs Iiito+coritwcriorl -Basic Reference Model: The basic model. ISO/IEC 7776: 1995, Information technology - Telecommunications and information exchange between syslems - High-level data link control procedures - Desc
19、ription of the X.25 LA PB-compatible DTE data link procedures. 1 ISO/IEC 11575 : 1995 (E) 0 ISODEC ISO/IEC 8802-2: 1994, Information technology - Telecommunications and information exchange bemeen systems - Local and metropolitan area networks - Specijk requirements - Part 2: Logical link control. I
20、SO/IEC 8886: 1992, informarion ieclurology - Telecommunications aizd inf11rn7atioii excltartge between systems - Data Link service definition for Upen Systems Interconnection. ITU-T Recommendation X.210 (1 993) I ISO/IEC 1073 1 : 1994, Information technology - Open Systems Interconnnection - Basic R
21、eference Model - Conventions for the definition of OSI services. 3 Definitions 3.1 This IntemationaI Standard uses the following terms defined in ITU-T Rec. X.200 I ISO/IEC 7498-1: DL-address DL-connection DL-connectionless-mode transmission DL-ent ity DL-group address DL-layer DL-protocol-data-unit
22、 DL-service access point DL-service access point address DL-service-data-unit DL-subsystem 3.2 This International Standard uses the following ternis defined in ITU-TRec. X.210 I ISOflEC I0731: DLS provider DLS user primitive request (primitive) indication (primitive) response (primitive) confirm (pr
23、imitive) 3.3 For the purposes of this Tnternational Standard, the following definitions apply: 3.3.1 frame: A DL-PDU. 3.3.2 instance of DL-communication: A DL connection or a single DL-connectionIess-illoe transmission. 4 Abbreviations BCC CL co DISC DL DLC DLS DLSAP DLSDU DM FRMR HDLC I LLC NRM PDU
24、 QOS SABM SABME SLP SNRM SNRME UA 2 balanced operation connectionless-mode class connect i on less-mode connection-mode disconnect Data Link Data Link connection Data Link service Data Link service access point Data Link service data unit disconnected mode frame reject High-level data link control i
25、nformation Logical Link Control normal response mode protocol data unit quaIity of service set asynchronous balanced mode set asynchronous balanced mode extended single link procedure set normal response mode set normal response mode extended unnumbered acknowledgment 0 ISO/lEC ISOlIEC 11575 : 1995
26、(E) ucc UI UNC unbalanced operation connectionIess-mode class unnumbered infomiation unbalanced operation nomd response mode class 5 Conformance There is no direct conformance of equipment to this International Standard considered in isolation. The provisions of this International Standard have norm
27、ative application to equipment implementing Network-layer protocols that are specified in terms of their use of the OS1 Data Link service. For such Network-layer protocols, this International Standard links the behaviour of the underlying Data Link protocols to the relevant features of the Data Link
28、 service, and thus provides the basis for establishing conformance of the Network-layer protocol implementations to the specified usage of the Data Link layer. NOTES 1 This International Standard therefore functions as “glue” between Network-layer protocol standards, written in terms of their use of
29、 the OS1 Data Link service, and Data Link protocol standards written - usually for historical reasons - without reference to the OS1 Data Link service. Conformance to such a Data Link protocol standard will be expressed entirely in fernis of the procedures and PDUs. etc specified in that standard; c
30、onformance to such a Network- layer standard in respect of its use of the Data Link layer will be expressed in terms of, for example. the transfer of NPDUs as DLSDUs. and (for the CO-DLS) of procedures that apply in the event of DL connection reset or DL connection relellse. This International Stand
31、ard specifies precisely how the procedures, etc of the Data Link protocol in question are to be interpreted in terms of the OSt Data Link Service. and therefore establishes a precise relationship between the specifications of the Network-layer protocol and of the Data Link protocol. 2 Use of the OS1
32、 Data Link service in Network-layer protocol specifications offers the benefits of layer-independence. in that such a Network-layer specification is availahle, without change. for use over new or alternntive Data Link technologies, provided only that the appropriate mapping is specified between the
33、OS1 Data Link service and the relevant DJta Link technology. 6 General principles of the protocol mappings 6.1 Data Link architecture The OS1 Data Link service defines the properties of individual instances of Dt-communication between pairs of DLS users.The definition is abstractly expressed in term
34、s of primitives and parunieters exchanged. at Data Link service access points (DLSAPs), between each DLS user and a single DLS provider: this is illustrated in figure 1. D tS DLSAP user DLS provider Figure 1 - Model of Data Link service provision Operation of the DLS provider is modelled in ternis o
35、f the exchange of DL-PDUs, in accordance with DL-protocols, between DL-entities (figure 2). Each DLSAF is attached to a unique DL-entiry; a given DL-entity can have one or more DLSAPs attached to it, depending upon system configuration and the nature of the underlying DL-protocols. When real equipme
36、nt is considered, a data link consists of two or more stations communicating according to a particular DL-protocol or set of related DL-protocols, together with the interconnecting media supporting infomiation exchange among the stations. Possible configurations of a real data link (see figure 3) in
37、clude: point-to-point data links, with just two stations (mappings MI and M5 are for protocols used in data links of this type); centralized multipoint data links, wirh one station controlling conlnlunication between itself and a number of subsidiary stations (mappings MZ and M6 are for protocols us
38、ed in data links of this type); distributed multipoint data links, with a number of stations any of which can communicate with any other (local area networks are of this type, see mappings M3 and M4). The definition of stations and data links has a logical diniension, deriving from the protocols use
39、d, in addition to the physical equipment used in constructing particular real dara links. A single real system can be atrsched to two or more data links, in which case it is considered to contain the corresponding number of distinct stations; a single real system can contain two or more stations att
40、ached to the same data link; and it is possible for a single set of conimunications equipment to support two or more distinct data links. 3 ISOlIEC 11575 : 1995 (E) Subsidiary 0 ISO/IEC Subsidiary Subsidiary The Data Link service model deals primarily with the properties of individual instances of D
41、L-communication. each occurring between a pair of DL-entities or, for mulricast coniniunication, between a single originating source DL-entity and a set of destination DL-entities. DL- protocols have to deal with multiple instances of communication, both between a given pair of DL-entities and. cert
42、ainly for data links of types (b) and (c) above, between different pairs (or niulticast sets) of DL-entities: representing the protocol facilities that support this forms a part of the specification of the mapping between the protocol and the DLS. Aspects to be considered include the number of DLSAP
43、s supported by a given station, the number of DL connections that can be active simultaneously at a DLSAP, and the DL addressing facilities that support discrimination among multiple stations. I I DLS provider Figure 2 - Structure of DLS provider a) Point-to-point data link, two stations only (e.g.
44、combined stations or peer stations) b) Centralized multi-point data link, communication between controlling station (eg, primary station or control station) and subsidiary stations (e.g.4 secondary stations or tributary stations) c) Distributed multipoint data link, any station to any station Fgure
45、3 - Types of data link configuration 4 0 ISO/IEC ISO/IEC 11575 : 1995 (E) 6.2 Modelling of service primitives Primitives are abstractions of the behaviour of real systenis engaging in data communication: in specifying the mapping between these abstract primitives and the activity of real hiplenienta
46、tions of DL-protocol entities. this allows freedom in modelling the timing of when primitives occur, so as to simplify the mapping specification. NOTE 1 - ISO/IEC 8886 explicitly allows this freedom; it defines the constraints on the sequence in which primitives can occur, but states that other cons
47、traints affect the ability of a DLS user or DLS provider to issue a primitive at any particular time. For primitives issued by the DLS user - those of types request and response - this International Standard uses a rendezvous model: that is, a primitive can only occur if both the DLS user and the lo
48、cal DLS provider are prepared for it to occur. This provides two valuable simplifications: occurrence of DLS-user issued primitives can aIways be related to the externally observable transmission of corresponding frames - the ability to transmit the frames is considered to be an essential part of th
49、e DLS provider being prepared for the primitive to occur; and there is no need to complicate the mapping by, for example. introducing any queueing of primitives that have been issued by the DLS user but have not yet resulted in any protocol activity. Conversely, for primitives issued by the DLS provider - those of types indication and confirm - it is convenient to simplify the model by considering primitives to occur as soon as the DLS provider is ready. NOTES 2 primitives is modelled as occurring after the requests are removed from such a queue, not when they are entered into the
