1、Reference number ISO/IEC 8208:2000(E) ISO/IEC 2000 INTERNATIONAL STANDARD ISO/IEC 8208 Fourth edition 2000-11-01 Information technology Data communications X.25 Packet Layer Protocol for Data Terminal Equipment Technologies de linformation Communication de donnes Protocole X.25 de couche paquet pour
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7、00 All rights reserved CONTENTS Page Forewordvi 1 Scope 1 2 Normative references 1 2.1 Identical Recommendations | International Standards .1 2.2 Paired Recommendations | International Standards equivalent in technical content2 2.3 Additional references .2 3 General considerations .2 3.1 Compatibili
8、ty with versions of Recommendation X.25 .3 3.2 Environments.5 3.3 Differences in DTE/DTE and DTE/DCE operation.5 3.4 Operation over circuit-switched connections.6 3.5 Provision of the OSI Network Service.7 3.6 External Packet Layer interactions.7 3.7 Logical channels 7 3.8 Packet Layer entity.8 3.9
9、Packet types .9 3.10 Procedures for initialization.9 4 Procedures for restart.9 4.1 Originating a restart request.10 4.2 Receiving a restart indication.12 4.3 Restart collision .12 4.4 Restart confirmation. 12 4.5 Determining “DTE” or “DCE” characteristics.12 5 Procedures for Virtual Call setup and
10、clearing 13 5.1 Ready state.13 5.2 Procedures for Virtual Call setup.13 5.3 Rejecting a call.15 5.4 Aborting a call request.15 5.5 Procedures for Virtual Call clearing 15 6 Procedures for data and interrupt transfer.16 6.1 States for data and interrupt transfer 17 6.2 Maximum User Data Field length
11、of DATA packets .17 6.3 Delivery Confirmation bit17 6.4 More Data mark . 18 6.5 Complete packet sequence.18 6.6 Qualifier bit18 6.7 Fragmentation and reassembly of messages.19 6.8 Procedures for interrupt .20 6.9 Transit delay of DATA packets21 7 Procedures for flow control21 7.1 Flow control.22 7.2
12、 Throughput characteristics and throughput classes25ISO/IEC 8208 : 2000(E) ISO/IEC 2000 All rights reserved iv 8 Procedures for reset . . 25 8.1 Originating a reset request .27 8.2 Receiving a reset indication. 27 8.3 Reset collision 27 8.4 Reset confirmation. 27 9 Effects of clear, reset, and resta
13、rt procedures on the transfer of packets . 27 10 Effects of Layers 1 and 2 on the Packet Layer 28 11 Error handling 28 11.1 The DIAGNOSTIC packet. 29 11.2 Nonreceipt of window-rotation information 29 11.3 Receipt of erroneous DATA packets . 30 12 Packet formats. 31 12.1 General. 31 12.2 Call setup a
14、nd call clearing packets . 33 12.3 DATA and interrupt packets 42 12.4 Flow control packets 44 12.5 Reset packets . 45 12.6 Restart packets . 47 12.7 DIAGNOSTIC packet 48 12.8 REJECT packet 49 12.9 Registration packets. 50 13 Procedures for optional user facilities . 52 13.1 On-line Facility Registra
15、tion 52 13.2 Extended and Super Extended Packet Sequence Numbering 59 13.3 D-bit Modification. 60 13.4 Packet Retransmission . 60 13.5 Incoming Calls Barred . 61 13.6 Outgoing Calls Barred . 61 13.7 One-way Logical Channel Outgoing 61 13.8 One-way Logical Channel Incoming . 61 13.9 Nonstandard Defau
16、lt Packet Sizes . 61 13.10 Nonstandard Default Window Sizes 61 13.11 Default Throughput Classes Assignment. 62 13.12 Flow Control Parameter Negotiation . 62 13.13 Throughput Class Negotiation Facilities 63 13.14 Closed User Group related facilities 64 13.15 Bilateral Closed User Group related facili
17、ties 68 13.16 Fast Select 69 13.17 Fast Select Acceptance 70 13.18 Reverse Charging. 70 13.19 Reverse Charging Acceptance . 70 13.20 Local Charging Prevention 70 13.21 Network User Identification (NUI) related facilities 71 13.22 Charging Information.71 13.23 ROA related facilities 73 13.24 Hunt Gro
18、up 73 13.25 Call Redirection and Call Deflection related facilities. 73 13.26 Called Line Address Modified Notification. 76 13.27 Transit Delay Selection and Indication 76 13.28 Alternative Addressing Related Facilities 76 13.29 TOA/NPI address subscription 78 13.30 Reference Number . 78 14 Procedur
19、es for optional ITUT s pecified DTE facilities.80 14.1 Calling Address Extension. 80 14.2 Called Address Extension 80 14.3 Minimum Throughput Class Negotiation 80 14.4 End-to-End Transit Delay Negotiation 81ISO/IEC 8208 : 2000(E) v ISO/IEC 2000 All rights reserved 14.5 Priority.81 14.6 Protection.81
20、 14.7 Expedited Data Negotiation.81 15 Format for Facility Field in call setup/clearing packets .82 15.1 General.82 15.2 Coding of the Facility Field for optional user facilities .83 15.3 Coding of the Facility Field for ITU-T specified DTE facilities89 16 Format for Registration Field in registrati
21、on packets92 16.1 General.92 16.2 Coding of the Registration Field for registration-facilities 93 17 Diagnostic codes 95 18 Timers and retransmission counts .101 19 State diagrams.105 20 State tables.111 21 Conformance .120 21.1 Static conformance.120 21.2 Protocol Implementation Conformance Stateme
22、nt 120 21.3 Dynamic conformance .120 Annexes A Private networks.123 B PICS Proforma .131 C Differences between various editions of ISO/IEC 8208.159 D Abbreviations169ISO/IEC 8208 : 2000(E) ISO/IEC 2000 All rights reserved vi Foreword ISO (the International Organization for Standardization) and IEC (
23、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 organization to deal with part
24、icular 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. International Standards are drafted in accordance with the ru
25、les given in the ISO/IEC Directives, Part 3. In the field of information technology, ISO and IEC have established 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 Interna
26、tional Standard requires approval by at least 75 % of the national bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such pate
27、nt rights. International Standard ISO/IEC 8208 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6, Telecommunications and information exchange between systems. This fourth edition cancels and replaces the third edition (ISO/IEC 8208:1995), which has be
28、en technically revised. Annexes A and B form a normative part of this International Standard. Annexes C and D are for information only.INTERNATIONAL STANDARD ISO/IEC 8208 : 2000(E) ISO/IEC 2000 All rights reserved 1 Information technology Data communications X.25 Packet Layer Protocol for Data Termi
29、nal Equipment 1 Scope This International Standard specifies the procedures, formats and facilities at the Packet Layer for Data Terminal Equipment (DTE) operating in conformance with ITU-T Recommendation X.25. Both Virtual Call and Permanent Virtual Circuit modes of operation are covered. The Packet
30、 Layer protocol specified herein can be used in both Open Systems Interconnection (OSI) and non-OSI environments. When used within the context of OSI, the Packet Layer protocol is encompassed in the Network Layer of the OSI Reference Model, ITU-T Rec. X.200 | ISO/IEC 7498-1. This International Stand
31、ard covers DTE operation at the Packet Layer when accessing a public or private packet-switched network conforming to ITU-T Recommendation X.25 by means of a dedicated path or a circuit-switched connection. It also covers the additional Packet Layer procedures necessary for two DTEs conforming to th
32、is International Standard to communicate directly (i.e., without an intervening packet-switched network) over a dedicated path, a circuit-switched connection, or a local area network (LAN). This International Standard also covers private networks that use ITU-T Recommendation X.25 to connect to pack
33、et-switched public data networks and that may also offer an X.25 interface to a DTE (see annex A). To evaluate conformance of a particular implementation, it is necessary to have a statement of which capabilities and options have been implemented. Such a statement is called a Protocol Implementation
34、 Conformance Statement (PICS), as defined in ITU-T Rec. X.290 | ISO/IEC 9646-1. Annex B provides the PICS proforma in accordance with the relevant guidance given in ITU- T Rec. X.296 | ISO/IEC 9646-7. The first edition of this International Standard was based on the 1984 CCITT Red Book text of Recom
35、mendation X.25. It also contained the necessary provisions for compatibility with the earlier 1980 CCITT Yellow Book text of Recommendation X.25. The second edition was based on the 1988 CCITT Blue Book text of Recommendation X.25. The third edition is based upon the 1993 version of X.25. This fourt
36、h edition is based on the 1996 version of X.25. Retained within this fourth edition are the necessary provisions for compatibility with the 1993, 1988, 1984 and 1980 versions of X.25. The differences between various editions of this International Standard are summarized in annex C. It should be note
37、d that this International Standard and ITU-T Recommendation X.25 as it applies to DTEs are different in scope. This International Standard contains the specifications that ITU-T Recommendation X.25 places on DTEs. In addition, this International Standard contains added specifications to facilitate i
38、nterworking between DTEs and to cover direct DTE-to-DTE operation. This broader scope has to be recognized in the application of this International Standard. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of th
39、is International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative
40、documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a register of currently valid I
41、TU-T Recommendations. 2.1 Identical Recommendations | International Standards 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.212 (1995) | ISO/IEC 8886 : 1996, Information tec
42、hnology Open Systems Interconnection Data link service definition ITU-T Recommendation X.213 (1995) | ISO/IEC 8348 : 1996, Information technology Open Systems Interconnection Network service definition ITU-T Recommendation X.263 (1998) | ISO/IEC TR 9577:1999, Information technology Protocol identifi
43、cation in the network layer ITU-T Recommendation X.273 (1994) | ISO/IEC 11577 : 1995, Information technology Open Systems Interconnection Network layer security protocol CCITT Recommendation X.612 (1992) | ISO/IEC 9574 : 1992, Information technology Provision of the OSI connection-mode network servi
44、ce by packet-mode terminal equipment connected to an integrated services digital network (ISDN)ISO/IEC 8208 : 2000(E) 2 ISO/IEC 2000 All rights reserved CCITT Recommendation X.613 (1992) | ISO/IEC 10588 : 1993, Information technology Use of X.25 Packet Layer Protocol in conjunction with X.21/X.21bis
45、 to provide the OSI connection- mode Network Service CCITT Recommendation X.614 (1992) | ISO/IEC 10732 : 1993, Information technology Use of X.25 Packet Layer Protocol to provide the OSI connection-mode Network Service over the telephone network 2.2 Paired Recommendations | International Standards e
46、quivalent in technical content - CCITT Recommendation T.50 (1992), International Reference Alphabet (IRA) ISO/IEC 646 : 1991, Information technology ISO 7-bit coded character set for information interchange - ITU-T Recommendation X.223 (1993), Use of X.25 to provide the OSI connection-mode network s
47、ervice for ITU-T applications ISO/IEC 8878 : 1992, Information technology Telecommunications and information exchange between systems Use of X.25 to provide the OSI Connection-mode Network Service - ITU-T Recommendation X.290 (1995), OSI conformance testing methodology and framework for protocol Rec
48、ommendations for ITU-T applications General concepts ISO/IEC 9646-1 : 1994, Information technology Open Systems Interconnection Conformance testing methodology and framework Part 1: General concepts - ITU-T Recommendation X.296 (1995), OSI conformance testing methodology and framework for protocol R
49、ecommendations for ITU-T applications Implementation Conformance Statements ISO/IEC 9646-7 : 1995, Information technology Open Systems Interconnection Conformance testing methodology and framework Part 7: Implementation Conformance Statements 2.3 Additional references CCITT Recommendation D.12 (1988), Measurement unit for charging by volume in the international packetswitched data communication service ITU-T Recommendation X.2 (1996), International data transmission services and optional user f
