1、STD-ITU-T RECMN X.75-ENGL L77b 4Bb2571 Ob274b7 BOT = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU x.75 (1 0/96) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUN KATION Public data networks - Transmission, signalling and switching Packet-switched signallin
2、g system between public networks providing data transmission services ITU-T Recommendation X.75 (Previously CCITT Recommendation) STDmITU-T RECMN X.75-ENGL L77b lBb259L 0b27470 521 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION _ ._ ., z: Services and facilities Interface
3、s X.l-X.19 X.20-X.49 Network aspects Maintenance Administrative arrangements Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specifications PICS proformas Protocol Identification Security Protocols Layer Managed Objects Conformance testing
4、General Satellite data transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS OPEN SYSTEM INTERCONNECTION INTERWORKING BETWEEN NETWORKS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN.1) Systems Management framework and a
5、rchitecture Management Communication Service and Protocol Structure of Management Information Management functions OS1 MANAGEMENT SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING X.90-X.149 X.150-X.179 X.180-X.199 X.2
6、00-X.299 X.200-X.209 X.2 1 O-X.2 1 9 X.220-X.229 X.230-X.239 X.240-X.259 X.260-X.269 X.270-X.279 X.280-X.289 X.290-X.299 X.300-X.399 X.300-X.349 X.350-X.399 X.400-X.499 X.500-X.599 X.600-X.699 X.600-X.629 X.630-X.649 X.650-X.679 X.680-X.699 X.700-X.799 X.700-X.709 X.710-X.719 X.720-X.729 x.730-x.799
7、 X.800-X. 849 X.850-X.899 X.85-X.859 X.860-X.879 X.880-X.899 X.900-X.999 For further details, please ref to ITU-T List of Recommendations. FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (IT). The ITU-T is responsible fo
8、r studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T
9、Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the IT-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation X.75 was revised by ITU-T Study Group 7 (1993-1996)
10、 and was approved under the WTSC Resolution No. 1 procedure on the 5th of October 1996. I NOTE i In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O IT 1997 All rights reserved. No pa
11、rt of this publication may be reproduced or utilized in any fom- or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing . A.2 Symbol definition of the state diagrams . A.3 Order definition of the state diagrams A.4 Symbol definition of the acti
12、on tables Annex . B - State diagrams for the packet layer interface between STEs for normal cases . Annex C -Actions taken by the STE on receipt of packets in a given state of the packet layer X/Y interface . Annex E - Coding of network generated diagnostic fields in X.75 clear, reset and restart pa
13、ckets . Annex F - Association of error conditions with cause and diagnostic codes . Annex D - Actions taken by the STE on time-outs in the packet layer Appendix I - Examples of multilink resetting procedures 1.1 Introduction 1.2 MLP reset initiated by a single STE . . 1.3 MLP reset initiated by both
14、 STEs simultaneously 2 2 2 3 3 4 4 4 7 20 30 40 40 40 41 42 43 46 46 47 47 48 63 67 73 76 76 76 76 85 95 95 95 95 96 97 100 105 107 110 115 115 115 116 Recommendation X.75 (10196) 11 Appendix II . Additional information on data signalling rates higher than 64 kbids . II.1 Use of time slot O to 2 Mbi
15、tls links . IIi2 Guidelines for data signalling rates higher than 64 kbitls in order to support high throughput . Appendix III - Guidelines for transmission over channels with long round trip delay and/or . transmission rates higher than 64 kbitls . 111.1 Preamble . 111.2 Common guidelines 111.3 Gui
16、delines for channels with long round trip delays operating at 64 kbitls . 111.4 Guidelines for circuits operating at 1920 kbids Appendix IV - Examples of the use of multi-selective reject option Page 116 116 117 118 118 118 118 119 120 . Recommendation X.75 (10/96) 111 SUMMARY This Recommendation de
17、scribes a packet-switched signalling system between public networks providing data transmission services. iv Recommendation X.75 (10/96) Recommendation X.75 PACKET-SWITCHED SIGNALLING SYSTEM BETWEEN PUBLIC NETWORKS PROVIDING DATA TRANSMISSION SERVICES (Provisional, Geneva, 1978; amended at Geneva, 1
18、980, Malaga-Torremolinos, 1984, Melbourne, 1988, Helsinki, 1993; revised in 1996) The establishment in various countries of public networks providing packet-switched data transmission services creates a need to standardize international interworking. The IT-T, considering (4 that Recommendation X.l
19、includes specific user classes of service for data terminal equipments operating in the packet mode, Recommendation X.2 defines user facilities, Recommendations X.25, X.28, X.29, X.31 and X.32 definite DTE/DCE interface characteristics and Recommendation X.96 defines call progress signals; (b) packe
20、t-switched data transmission services; (cl that Recommendations X.300, X.301 and X.302 define the general principles and arrangements for interworking between public data networks, and between public data networks and other public networks; that the logical links Al and G1 in an international connec
21、tion are defined in Recommendation X.92 for I (4 networks; that Recommendations X.320, X.322, X.323 and X.325 provide descriptions of interworking cases among (e) that Recommendation X. 180 defines the administrative arrangements for Intentional Closed User Groups and that Recommendation X. 18 1 def
22、ines the administrative arrangements for the provision of international Permanent Virtual Circuits; (0 data switching exchange should be defined independently as: that the necessq elements of the signalling terminal (STE) interface Recommendation at the gateway/transit Physical layer - the mechanica
23、l, electrical, functional and procedural Characteristics to activate, maintain and Linklayer - the link layer procedures for data interchange across the interface between the signalling Packet layer - the packet format and signalling procedures for the exchange of packets containing control deactiva
24、te the physical link at the signalling terminal interface; terminals; information and user data at the Signalling terminal interface; (g) networks providing packet-switched data transmission services; (h) plans for public networks including ISDN, that Recommendations X.134, X.135, X.136 and X.137 de
25、fine the quality of service parameters in public that Recommendations X. 1 1 O, X. 12 1, E. 164 and E. 166K 122 describe the routing principles and numbering unanimously declares (1) specified in the Introduction: Basic syslem strucure; (2) that the mechanical, electrical, functional and procedural
26、Characteristics to activate, maintain and deactivate the physical link at the signalling terminal interface should be as specified in clause 1: Physical layer - Characteristics of the signalling terminaUphysica1 circuit interface; (3) that the link layer procedures which operate over the physical ci
27、rcuits and provide a mechanism for reliable transport of packets at the signalling terminal interface should be as specified in clause 2:Link layerprocedures between signalling terminals; that the basic system structure of the signalling and data transfer procedures in terms of elements should be as
28、 Recommendation X.75 (10/96) 1 STD-ITU-T RECMN X-75-ENGL L77b 48b257L Ob27q7b T4T (4) terminal interface should be as specified in clause 3: Packet layer procedures between signalling terminals; that the packet signalling procedures for the exchange of call information and user data at the signallin
29、g (5) clause 4: Packet formats for virtual calls andpermanent virtual circuits; that the packet format for packets exchanged at the signalling terminal interface should be as specified in (6) should be as specified in clause 5: Procedure and formats for user facilities and network utilities. that th
30、e procedure and formats for user facilities and network utilities at the signalling terminal interface O Introduction 0.1 General This Recommendation defines the characteristics and operation of a signalling system for use on interconnecting links between various types of public networks to provide
31、internetwork data transmission services, It permits the transfer of call control and network control information and user traffic. This Recommendation applies to all links between packet-switched public data networks in different countries and also in a number of cases of international links with IS
32、DNs as specified in Recommendation X.300. These include links between ISDNs and packet-switched public data networks and links between ISDNs providing packet-switched data transmission services as defined in Recommendation X.31. It may also be used on such links where the two public networks are in
33、the same country. Each internetwork link comprises two directly connected Signalling Terminals (STEs) each within a public network. Transmission facilities between the two STEs may comprise either one or a number of circuits. Each STE is associated with one end of one link and is part of an exchange
34、 or exchange function in the public network. Certain parts of this Recommendation apply in only a limited range of interworking situations; these are clearly indicated in the text. Some concern links between public networks in the same country, and others concern links where at least one public netw
35、ork is not a packet-switched data network. The protocol elements included in this Recommendation can be used to support the Network Layer Service for interworking situations. 0.2 Elements The system is made up of communicating elements which function independently and are therefore defined separatel
36、y. These elements are: a) the physical circuits which comprise transmission facilities, and a set of mechanical, electrical functional and procedural interface characteristics between the transmission facilities and the signalling terminals and which provide a mechanism for information transfer betw
37、een two signalling terminals; b) the link layer procedures which operate over the physical circuits and provide a mechanism for reliable transport of packets between the two signalling terminals independently of the particular types of physical circuit in use; c) the packet layer procedures which us
38、e the link layer procedures and provide a mechanism for the exchange of call control information and user trafic between the two signalling terminals. 2 Recommendation X.75 (1096) 0.3 Basic system structure Packet layer procedures The basic system structure of the signalling procedures, in terms of
39、the elements, is shown in Figure 1. Link I layer procedures - I I I Higher layer fundions -call m -networkmtrd -usertraffic Signalling terminal (STE) I I I I I II I l I l I I_I I Exchange X or Y I Transmission + fadliies XN intelface TO71 7740-93ldOl FIGURE 1X.75 Basic system structure of Signalling
40、 procedures NOTE - Applicable to this Recommendation: a) STE-X denotes the STE of the exchange under consideration on the link concerned; b) STE-Y denotes the STE of the other exchange under consideration on the link; c) the STE-WSTE-Y interface is abbreviated to the X/Y interface; d) multiplex XN i
41、nterfaces may be used between two networks. In this case, each XN interface behaves according to the physical, link and packet layer formats and procedures within this Recommendation. 1 Physical layer - Characteristics of the signalling terminaUphysica1 circuit interface The characteristics of the s
42、ignalling terminal/physical circuit interface, defined as the physical layer element, shall be in accordance with Recommendation G.703, for physical circuits having a bearer rate of 64 kbit/s and optionally, by bilateral agreement, 2 Mbit/s. For 2 Mbit/s, the fiame structure conforms to Recommendati
43、on G.704. Time slot O will be used for the detection of faults (Recommendation G.732), the indication of alarms, and for maintenance facilities (loop backs). Time slot 16 is not used in order to have the same structure as an H12 channel. The remaining 30 time slots should be used as one single bit s
44、tream of 1920 kbit/s. Further information is given in Appendix II. In addition, Administrations may use for digital circuits any other recognized rate (e.g. 1.544 Mbit/s, n times 64 kbids channels) by bilateral agreement. However, for an interim period by bilateral agreement, any other recognized ra
45、tes could be used for analogue circuits, in which case the characteristics of the signalling terminallphysical circuit interface shall be in accordance with the appropriate V-Series Recommendations. Each physical circuit of the link must be capable of supporing duplex operation. In the case of inter
46、national interworking between packet-switched public data networks,- the link is assumed to be data link Al and/or data link G1 in terms of the hypothetical reference connections defined in Recommendation X.92. Recommendation X.75 (10/96) 3 STD-ITU-T RECMN X.75-ENGL L77b 48b2571 Ob27978 812 REJ reco
47、very (2.3.5.2.1) (2.3.5.2.2) SREJ recovery 2 Link layer procedures between signalling terminals Non-extended Extended Super (modulo 8) (modulo 128) (modulo 32768) mandatory subscription-time option prohibited (Note) (Note) prohibited subscription-time option mandatory 2.1 Scope and field of applicat
48、ion 2.1.1 In order to provide a mechanism for the reliable transport of packets between two signalling terminals, it is necessary to define a procedure which can accept and deliver packets to the packet layer when either single or multiple physical circuits are employed. A multiplicity of physical c
49、ircuits is required if the effects of circuit failures are not to disrupt the packet layer operation. 2.1.2 The Single Link Procedure (SLP) described in 2.2 to 2.4 is used for data interchange over a single physical circuit, conforming to the description given in clause 1, between two STEs. When multiple physical circuits are employed in parallel, this single link procedure is used independently on each circuit and the Multilink procedure (MLP) described in 2.5 may be used for data interchange over these multiple p
