1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.76TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2003) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Public data networks Transmission, signalling and switching Network-to-network interface between public networks providing PVC and/or SVC
2、frame relay data transmission service ITU-T Recommendation X.76 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS PUBLIC DATA NETWORKS Services and facilities X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X
3、.150X.179 Administrative arrangements X.180X.199 OPEN SYSTEMS INTERCONNECTION Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260
4、X.269 Security Protocols X.270X.279 Layer Managed Objects X.280X.289 Conformance testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.369 IP-based networks X.370X.399 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND
5、 SYSTEM ASPECTS Networking X.600X.629 Efficiency X.630X.639 Quality of service X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAGEMENT Systems Management framework and architecture X.700X.709 Management Communication Service and Protoc
6、ol X.710X.719 Structure of Management Information X.720X.729 Management functions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, Concurrency and Recovery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 F
7、or further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. X.76 (02/2003) i ITU-T Rec. X.76 Network-to-network interface between public networks providing PVC and/or SVC frame relay data transmission service Summary This Recommendation describes the frame relay network-to-netw
8、ork interface intended for the interconnection of public networks providing PVC and/or SVC frame relay data transmission service. The signalling at the NNI for frame relay SVC is applicable to public data networks supporting ITU-T Rec. X.36 at the DTE/DCE interface. Details of physical layer, data t
9、ransfer and signalling procedures for SVC and PVC at the network-to-network interface are defined. PVC signalling procedures have been enhanced with a new segmentation capability procedure to increase the number of PVC status reports. Recognizing that frame relay bearer services and signalling are n
10、ot supported by ISDN local exchanges, Case B has been removed from ITU-T Rec. Q.933 (2003). Consequently this version of ITU-T Rec. X.76 no longer supports the NNI signalling capabilities specific to ITU-T Rec. Q.933 (1995) Case B. This revision replaces ITU-T Rec. X.76 (2000). This revised ITU-T Re
11、c. X.76 (2003) is in alignment with the latest release of ITU-T Recs Q.933 (2003) and X.36 (2003). Source ITU-T Recommendation X.76 was approved by ITU-T Study Group 17 (2001-2004) under the ITU-T Recommendation A.8 procedure on 13 February 2003. ii ITU-T Rec. X.76 (02/2003) FOREWORD The Internation
12、al Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations
13、on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of
14、 ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is
15、 used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with t
16、he Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required o
17、f any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual P
18、roperty Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. Howe
19、ver, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2003 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. I
20、TU-T Rec. X.76 (02/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and definitions . 2 4 Abbreviations 3 5 Conventions 3 6 Physical layer 3 7 Reference configuration 4 8 Service parameters and service quality. 4 8.1 Scope 4 8.2 Service parameters 4 8.3 Service quality 5 9 Data link transfe
21、r control 6 9.1 General . 6 9.2 Frame format 6 9.3 Addressing 7 9.4 Transmission considerations 9 10 Frame relay SVC signalling . 11 10.1 General . 11 10.2 Signalling channel 12 10.3 State definitions 14 10.4 Message definitions 14 10.5 General message format and information element coding. 20 10.6
22、Call establishment 44 11 Additional procedures for PVCs using unnumbered information frames 60 11.1 Overview 60 11.2 Message definition 61 11.3 Message specific information elements 62 11.4 Description of procedures. 64 11.5 Bidirectional aspects of operation 69 11.6 Asynchronous PVC STATUS message
23、70 11.7 System parameters 71 12 Congestion control 72 Annex A Signalling for switched PVC (SPVC) . 72 A.1 Messages needed for SPVC establishment. 74 A.2 Called party SPVC information element 74 A.3 Calling party SPVC information element. 75 A.4 SPVC Procedures . 76 iv ITU-T Rec. X.76 (02/2003) Page
24、Annex B Usage of cause and location 81 B.1 Location field generation 81 B.2 Cause values . 82 B.3 Coding of the diagnostic field 91 Annex C Enhancements to PVC management procedures . 93 C.1 Introduction 93 C.2 List of changes to clause 11 93 Appendix I Network congestion scenarios . 94 Appendix II
25、International network identification according to ITU-T Rec. X.125 for networks providing frame relay services and numbered under the E.164 numbering plan . 95 II.1 Introduction 95 II.2 Assignment and notification process 95 Appendix III Call state diagrams at one STE side of the NNI 95 III.1 Symbol
26、 definition of the call state diagrams 95 Appendix IV Action taken by the STE on receipt of a message in a given call state at one side of NNI. 98 ITU-T Rec. X.76 (02/2003) 1 ITU-T Rec. X.76 Network-to-network interface between public networks providing PVC and/or SVC frame relay data transmission s
27、ervice 1 Scope Recognizing that public networks are offering the frame relay data transmission service, there is a need for a standard network-to-network interface to enable interworking. This Recommendation provides the structural details required to implement such an interface. Procedures for PVC
28、and SVC operation are provided. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provision of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other re
29、ferences are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The referen
30、ce to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation E.164/I.331 (1997), The international public telecommunication numbering plan. ITU-T Recommendation E.166/X.122 (1998), Numbering plan interworking for the E.
31、164 and X.121 numbering plans. ITU-T Recommendation G.703 (2001), Physical/electrical characteristics of hierarchical digital interfaces. ITU-T Recommendation G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. ITU-T Recommendation I.122 (
32、1993), Framework for frame mode bearer services. ITU-T Recommendation I.233.1 (1991), Frame mode bearer services: ISDN frame relaying bearer service. ITU-T Recommendation I.370 (1991), Congestion management for the ISDN frame relaying bearer service. ITU-T Recommendation I.372 (1993), Frame relaying
33、 bearer service network-to-network interface requirements. ITU-T Recommendation I.430 (1995), Basic user-network interface Layer 1 specification. ITU-T Recommendation I.431 (1993), Primary rate user-network interface Layer 1 specification. ITU-T Recommendation Q.850 (1998), Usage of cause and locati
34、on in the Digital Subscriber Signalling System No. 1 and Signalling System No. 7 ISDN User Part. ITU-T Recommendation Q.920 (1993), ISDN user-network interface data link layer General aspects. ITU-T Recommendation Q.921 (1997), ISDN user-network interface Data link layer specification. 2 ITU-T Rec.
35、X.76 (02/2003) ITU-T Recommendation Q.922 (1992), ISDN data link layer specification for frame mode bearer services. ITU-T Recommendation Q.931 (1998), ISDN user-network interface layer 3 specification for basic call control. ITU-T Recommendation Q.933 (2003), ISDN Digital subscriber Signalling Syst
36、em No. 1 (DSS1) Signalling specifications for frame mode switched and permanent virtual connection control and status monitoring. ITU-T Recommendations Q.951.x-series, Stage 3 service description for number identification supplementary services using DSS1. ITU-T Recommendation T.50 (1992), Internati
37、onal Reference Alphabet (IRA) (Formerly International Alphabet No. 5 or IA5) Information technology 7-bit coded character set for information interchange. ITU-T Recommendation X.36 (2003), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for public data ne
38、tworks providing frame relay data transmission service by dedicated circuit. ITU-T Recommendation X.37 (1995), Encapsulation in X.25 packets of various protocols including frame relay. ITU-T Recommendation X.92 (1988), Hypothetical reference connections for public synchronous data networks. ITU-T Re
39、commendation X.121 (2000), International numbering plan for public data networks. ITU-T Recommendation X.124 (1999), Arrangements for the interworking of the E.164 and X.121 numbering plans for frame relay and ATM networks. ITU-T Recommendation X.125 (1998), Procedure for the notification of the ass
40、ignment of international network identification codes for public frame relay data networks and ATM networks numbered under the E.164 numbering plan. ITU-T Recommendation X.212 (1995) | ISO/IEC 8886:1996, Information technology Open Systems Interconnection Data link service definition. ITU-T Recommen
41、dation X.213 (2001) | ISO/IEC 8348:2002, Information technology Open Systems Interconnection Network service definition. 3 Terms and definitions This Recommendation defines the following terms: a) Committed Information Rate (CIR) as in 8.2.4; b) Committed Burst Size (Bc) as in 8.2.2; c) Excess Burst
42、 Size (Be) as in 8.2.3; d) Committed Rate Measurement Interval (Tc) as in 8.2.5; e) Access Rate (AR) as in 8.2.1; f) Maximum octet length of frame relay information field (N203) as in 8.2.6; g) N391 as in 11.4 and Table 32; h) N392 as in 11.4 and Table 32; ITU-T Rec. X.76 (02/2003) 3 i) N393 as in 1
43、1.4 and Table 32; j) T391 as in 11.4 and Table 33; k) T392 as in 11.4 and Table 33. NOTE The names of the timers and counters in items g) to k) are aligned with Annex A/Q.933 terminology. 4 Abbreviations This Recommendation uses the following abbreviations: AR Access Rate Bc Committed Burst Size Be
44、Excess Burst Size BECN Backward Explicit Congestion Notification C/R Command/Response CIR Committed Information Rate D/C DLCI Extension/Control Indication Bit DCE Data Circuit-terminating Equipment DE Discard Eligibility indicator DLCI Data Link Connection Identifier DTE Data Terminal Equipment EA A
45、ddress Field Extension FCS Frame Check Sequence FECN Forward Explicit Congestion Notification FRDTS Frame Relay Data Transmission Service LAPF Link Access Procedure for Frame mode bearer service PDN Public Data Network PVC Permanent Virtual Circuit SPVC Switched Permanent Virtual Circuit STE Signall
46、ing Terminal SVC Switched Virtual Circuit Tc Committed Rate Measurement Interval VC Virtual Circuit 5 Conventions No special conventions are employed within this Recommendation. 6 Physical layer The characteristics of the network-to-network interface, defined as the physical layer element, shall be
47、in accordance with ITU-T Rec. G.703. When used, the frame structure conforms to ITU-T Rec. G.704. In the case of 2 Mbit/s, time slot 0 is used to perform fault detection (see ITU-T Rec. G.732). Time slot 16 may either be used or not used, resulting in an access rate of 1984 kbit/s or 1920 kbit/s res
48、pectively. 4 ITU-T Rec. X.76 (02/2003) Other recognized rates may also be used, in which case the signalling terminal/physical circuit interface shall be in accordance with the appropriate V or X-series Recommendations, for example: V.24; V.35; V.36; X.21. Each physical circuit must be able to suppo
49、rt duplex operation. In the case of international interworking between public data networks providing FRDTS, the link is assumed to be data link A1 and/or data link G1 in terms of the hypothetical reference connections defined in ITU-T Rec. X.92. NOTE The use of SDH Interface is for further study. 7 Reference configuration Figure 1 illustrates the possible locations of the network-to-network interface. The interfaces connect public data networks providing
