1、BRITISH STANDARD BS ISO/IEC 14765:1997 Information technology Framework for protocol identification and encapsulation ICS 35.100.01BSISO/IEC14765:1997 This British Standard, having been prepared under the directionof the DISC Board, waspublished under the authorityof the Standards Boardand comes int
2、o effect on 15 December 1997 BSI 04-2000 ISBN 0 580 28856 0 National foreword This British Standard reproduces verbatim ISO/IEC14765:1997 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee IST/6, Data communications, which has
3、the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in th
4、e UK. A list of organizations represented on this committee can be obtained on request to its secretary. From 1 January1997, all IEC publications have the number60000 added to the old number. For instance, IEC27-1 has been renumbered as IEC60027-1. For a period of time during the change over from on
5、e numbering system to the other, publications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International St
6、andards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Sta
7、ndard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theISO/IEC title page, pages ii to iv, pages 1 to 18 and a back cover. This standard has been updated (see copyright date) and may have had
8、amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO/IEC14765:1997 BSI 04-2000 i Contents Page National foreword Inside front cover Foreword iii Text of ISO/IEC 14765 1ii blankBSISO/IEC14765:
9、1997 ii BSI 04-2000 Contents Page Foreword iii 1 Scope 1 2 Normative references 1 2.1 Identical Recommendations|International Standards 1 2.2 Additional references 1 3 Abbreviations 1 4 Definitions and concepts 2 4.1 Basic Reference Model concepts 2 4.2 Additional definitions and concepts 2 5 Overvi
10、ew 2 5.1 General 2 5.2 Interworking and encapsulation 3 6 Principles of protocol identification 3 6.1 Need for protocol identification 3 6.2 Protocol identifier registries and values 3 6.3 Protocol identification methods 5 6.4 Protocol identifiers 5 7 Principles of protocol encapsulation 6 7.1 Encap
11、sulation function 6 7.2 Protocol encapsulation methods 8 7.3 Relationships among EFs, EdPs, and EgPs 9 Annex A Current Recommendations|International Standards supporting PIE principles 13 Annex B Examples of protocol identification and encapsulation methods 15 Figure 1 Framework for protocol identif
12、ication and encapsulation principles 4 Figure 2 Relationship of IPI and SPI 6 Figure 3 Generic operation of an encapsulation function 7 Figure 4 Possible relationships of EdPs and EgPs 8 Figure 5 Combination of multiple EFs over a single EgP 9 Figure 6 One PDU of only supported EdP encapsulated in E
13、gP 10 Figure 7 Multiple PDUs of only supported EdP encapsulated in EgP 10 Figure 8 Multiple PDUs of one of the EdPs encapsuled in EgP 10 Figure 9 PDUs from multiple EdPs encapsulated in EgP 11 Figure 10 PDUs from same EdP encapsulated in EgP 11 Figure 11 One PDU of EDP encapsulated within multiple P
14、DUs of EgP 12 Figure 12 Relationships among EFs, EdPs, and EgPs 12 Figure A.1 Relationship of Recommendations|International Standards supporting principles of protocol identification and encapsulation 14 Figure B.1 ISDN D-channel with “SAPI” identification 15 Figure B.2 Q.931 Identification by Low L
15、ayer Compatibility (LLC) Information Element in ISDN 16 Figure B.3 Identification by Logical Link Control Address in LANs 17 Figure B.4 ITU-T Rec. X.263|ISO/IEC TR 9577 IPI 17 Figure B.5 ITU-T Rec. X.263 ISO/IEC TR 9577 SPI in X.25 call request 18 Figure B.6 ITU-T Rec. X.264 and ISO/IEC 11570 identi
16、fication of Transport Protocols 18 Descriptors: Data processing, information interchange, telecommunications, network interconnection, open systems interconnection, data transfer, protocols, identification methods.BSISO/IEC14765:1997 BSI 04-2000 iii Foreword ISO (the International Organization for S
17、tandardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organ
18、ization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technolo
19、gy, ISO and IEC have established a joint technical committee, ISO/IEC JTC1. 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 least75% of the national bodies casting a
20、vote. International Standard ISO/IEC14765 was prepared by Joint Technical Committee ISO/IEC JTC1, Information technology, Subcommittee SC6, Telecommunications and information exchange between systems, in collaboration with ITU-T. The identical text is published as ITU-T Recommendation X.260. Annex A
21、 and Annex B of this International Standard are for information only.iv blankBSISO/IEC14765:1997 BSI 04-2000 1 1 Scope In a layered approach to protocol architecture, protocols have a relationship to one another such that a protocol at layer (n) uses the services of the layer below it the (n1) servi
22、ces which, in turn, are provided by a layer (n1) protocol. One of the services used by a layer (n) protocol is the encapsulation of its (n) Protocol Data Units (PDUs) in a way which is transparent to it. Such encapsulation is realized by the carriage of the (n) PDUs as user data in an (n 1) Service
23、Data Unit (SDU). In a limited case, the operation of a particular protocol at layer (n1) implies the operation, above layer (n 1), of a single layer (n) protocol or single set of related (n) / (n + 1). protocols. However, in a more general case, there may be more than one protocol (or set of related
24、 protocols starting) at layer (n) that can operate above layer (n 1) in a given environment. In such cases, there is a need for explicit identification of the protocol (or set of protocols starting) at layer (n). There also may be a need to manipulate the (n 1) protocol (i.e.the encapsulating protoc
25、ol) in certain ways specific to the layer (n) protocol (i.e.the encapsulated protocol). Such manipulations form the basis of a set of procedures that must be specified for the layer (n) protocol. The above observations regarding protocol identification and encapsulation are also applicable in cases
26、where an (n) layer is further divided into sublayers. Cases in which an (n) protocol operates for the purpose of establishing a parallel universe of protocols (regardless of the layered structure of that universe) also give rise to a need for the (n) protocol to be able to identify the protocol(s) i
27、n the parallel universe. In these cases, however, there is no encapsulating/encapsulated relationship between the (n) protocol and the parallel universe set of protocols. The above principles lead to a need to establish a framework for protocol identification and encapsulation. These principles appl
28、y to the relationship between two protocols (recognizing that one of them may be a set of related protocols) and can be applied recursively. This Recommendation|International Standard provides a framework for explicit protocol identification and for protocol encapsulation. Implicit protocol identifi
29、cation (see4.2) is beyond the scope of this Recommendation|International Standard. 2 Normative references The following Recommendations and International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation|International Standard. At the ti
30、me of publication, the editions indicated were valid. All Recommendations and International Standards are subject to revision, and parties to agreements based on this Recommendation|International Standard are encouraged to investigate the possibility of applying the most recent edition of the Recomm
31、endations and International Standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid ITU-T Recommendations. 2.1 Identical Recommendations| International St
32、andards ITU-T Recommendation X.200 (1994)| ISO/IEC 7498-1:1994, Information technology Open Systems Interconnection Basic Reference Model: The Basic Model. ITU-T Recommendation X.263 (1995)| ISO/IEC TR9577:1996, Information technology Protocol identification in the network layer. 2.2 Additional refe
33、rences ITU-T Recommendation X.37 (1995), Encapsulation in X.25 packets of various protocols including frame relay. ISO/IEC 13515 1) , Information technology Telecommunications and information exchange between systems Generic Multiprotocol Encapsulation (GME): Application to frame relay and ATM. 3 Ab
34、breviations 1) Presently at the stage of draft. EdP Encapsulated Protocol EF Encapsulation Function EgP Encapsulating Protocol EPIF Encapsulated Protocol Information Field IdP Identified Protocol(s) IgP Identifying Protocol IPI Initial Protocol Identifier PCI Protocol Control Information PDU Protoco
35、l Data Unit PEM Protocol Encapsulation Method PId Protocol Identification PIE Protocol Identification and EncapsulationBSISO/IEC14765:1997 2 BSI 04-2000 4 Definitions and concepts 4.1 Basic Reference Model concepts The following concepts from ITU-T Rec. X.200| ISO/IEC 7498-1 are used here: a) concat
36、enation; b) layer; c) protocol; d) Protocol Control Information (PCI); e) Protocol Data Unit (PDU); f) protocol identification; g) protocol identifier; h) segmentation/reassembly; i) Service Data Unit (SDU); j) sublayer. 4.2 Additional definitions and concepts the definitions and concepts below appl
37、y to this Recommendation|International Standard 4.2.1 explicit protocol identification method an explicit PIM is one in which Protocol Control Information (PCI) is used to identify a protocol, a set of related protocols, or a family of protocols 4.2.2 implicit protocol identification method an impli
38、cit PIM is one in which there is no PCI used to identify a protocol. Identification occurs through mechanisms such as coupling in a Recommendation or International Standard of an IgP with an IdP e.g.stating that a specific (n) protocol is used above an (n 1) protocol; association of a physical port
39、of a system with one or a set of related protocols; or association at provisioning of a “permanent” connection 4.2.3 set of alternative protocols given protocols prot 1 , prot 2 , etc., then prot 1 , prot 2 , etc. all operate at the same layer or sublayer 4.2.4 set of related protocols given protoco
40、ls prot 1 , prot 2 , etc., then prot 1operates at layer (n), prot 2operates at layer (n +1), etc. (where the layers may also be hierarchical sublayers) 4.2.5 family of protocols given a set of alternative protocols prot 1 , prot 2 , etc., a single identifier is used to identify the set of alternativ
41、e protocols as a whole, thereby requiring additional methods to identify one member of the family 5 Overview 5.1 General As discussed above, there may exist a relationship between protocols that gives rise to a need for one protocol the Identifying Protocol (IgP) to identify one of a set of alternat
42、ive protocols, a set of related protocols, or a family of protocols the Identified Protocol(s) (IdP). As a result of the identification process, a second relationship may be created between an Encapsulating Protocol (EgP) and an Encapsulated Protocol(s) (EdP). In some cases, the IgP and the EgP may
43、be the same protocol. It is usually the case that an IdP and an EdP are the same. To provide a basis for developing the necessary relationships among specific protocols, a framework is developed here to set out the principles of Protocol Identification and Encapsulation (PIE). These principles recog
44、nize the following aspects of PIE: a) development of Protocol Identification Methods (PIMs) for identifying an IdP (e.g.the location in the IgP such as in a particular field: header, trailer, etc. used to identify the IdP); b) for each PIM, registration of values of IdPs; c) requirement on an IgP to
45、 specify the PIM it uses to identify IdPs and any further IgP-specific procedures involving the PIM; d) development of Protocol Encapsulation Methods (PEMs) for use by EgPs; and e) specification of operations (e.g.limitations, specific manipulations, etc.) of an EgP for a specific EdP. The above asp
46、ects are depicted inFigure 1. Annex A presents the current status of Recommendations and International Standards in alignment with the framework depicted inFigure 1. PIM Protocol Identification Method SDU Service Data Unit SPI Subsequent Protocol IdentifierBSISO/IEC14765:1997 BSI 04-2000 3 5.2 Inter
47、working and encapsulation Interworking and encapsulation of protocols are two closely related concepts. For the purposes of this Recommendation|International Standard, the following distinctions are made. Interworking occurs between two or more protocols at the same layer (or sublayer). It is concer
48、ned only with the semantic aspects of the (n) layer protocols. In particular, interworking is concerned with the transformation between the semantics of an (n) layer protocol used on one interface and the semantics of other (n) layer protocols used on the other interfaces. The protocols used on the
49、different interfaces may or may not be the same. The transformation between protocols may result in the preservation of the semantic content of all protocols on an end-to-end basis. The transformation only applies to the set of abstract capabilities (or service) which the protocols have in common. On the other hand, the transformation may result in a loss of semantic content when crossing interfaces. Encapsulation (or tunneling as it is sometimes called) occurs when a given protocols PDU (o
