1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.371/Y.1402 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2001) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Interworking between networks IP-based networks SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS Interne
2、t protocol aspects Interworking General arrangements for interworking between Public Data Networks and the Internet ITU-T Recommendation X.371/Y.1402 (Formerly CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS PUBLIC DATA NETWORKS Services and faciliti
3、es X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X.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.2
4、20X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260X.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 syste
5、ms X.350X.369 IP-based networks X.370X.399 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND 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.6
6、99 OSI MANAGEMENT Systems Management framework and architecture X.700X.709 Management Communication Service and Protocol 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 Recov
7、ery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 For further details, please refer to the list of ITU-T Recommendations. ITU-T X.371/Y.1402 (02/2001) i ITU-T Recommendation X.371/Y.1402 General arrangements for interworking between
8、Public Data Networks and the Internet Summary This Recommendation defines general arrangements for interworking between Public Data Networks and the Internet. It includes reference configurations, general packet handling and other general arrangements required for various interworking cases where PS
9、PDNs and networks providing FRDTS are involved. Source ITU-T Recommendation X.371/Y.1402 was prepared by ITU-T Study Group 7 (2001-2004) and approved under the WTSA Resolution 1 procedure on 2 February 2001. ii ITU-T X.371/Y.1402 (02/2001) FOREWORD The International Telecommunication Union (ITU) is
10、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 on them with a view to standardizing
11、 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 ITU-T Recommendations is covered by
12、 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 used for conciseness to indicate bo
13、th a telecommunication administration and a recognized operating agency. 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 e
14、vidence, validity or applicability of claimed Intellectual Property 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 not received notice of intellectual property, protected by patents, whic
15、h may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2002 All rights reserved. No part of this publication may be reproduced or utilized in a
16、ny form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T X.371/Y.1402 (02/2001) iii CONTENTS Page 1 Scope. 1 2 References. 1 3 Terms and definitions . 2 4 Abbreviations 2 5 Conventions 3 6 Interworking between the Internet
17、 and PSPDNs 3 6.1 General arrangements for the access cases . 3 6.1.1 Reference configuration 3 6.1.2 IP packet handling . 3 6.1.3 ARE procedures. 4 6.2 General arrangements for the concatenation case 1 (Concatenation of two Internet subnetworks via a PSPDN). 5 6.2.1 Reference configuration 5 6.2.2
18、IP packet handling . 5 6.2.3 ARE procedures. 6 6.3 General arrangements for the concatenation case 2 (Concatenation of two PSPDNs via the Internet) 6 6.3.1 Reference configuration 6 6.3.2 IP packet handling . 7 6.3.3 ARE procedures. 7 7 Interworking between the Internet and FRPDNs 7 7.1 General arra
19、ngements for the access cases . 7 7.1.1 Reference configuration 7 7.1.2 IP packet handling . 8 7.1.3 ARE procedures. 9 7.2 General arrangements for the concatenation case. 9 7.2.1 Reference configuration 9 7.2.2 IP packet handling . 10 7.2.3 ARE procedures. 10 7.3 General arrangements for the concat
20、enation case 2 (Concatenation of two FRPDNs via the Internet) . 11 7.3.1 Reference configuration 11 7.3.2 IP packet handling . 11 7.3.3 ARE procedures. 12 ITU-T X.371/Y.1402 (02/2001) 1 ITU-T Recommendation X.371/Y.1402 General arrangements for interworking between Public Data Networks and the Inter
21、net 1 Scope This Recommendation specifies general arrangements for interworking between the Internet and Public Data Networks (PDNs) among which PSPDN and FRPDN are considered. Three possible cases are defined: the case where the IP-TE connected to the PDN accesses the Internet via the PDN (access c
22、ase); the case where two Internet subnetworks are concatenated via the PDN (Concatenation case 1); the case where two PDNs are concatenated via the Internet (Concatenation case 2). The following arrangements are specified in this Recommendation: 1) reference configuration; 2) interface characteristi
23、cs for UNI and NNI; 3) addressing mechanism; 4) functionality of the Access Unit (AU), InterWorking Function (IWF) and the Adapter. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommenda
24、tion. At the time of publication, the editions indicated were valid. All Recommendations and other references 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
25、listed below. A list of the currently valid ITU-T Recommendations is regularly published. 1 ITU-T E.164 (1997), The international public telecommunication numbering plan. 2 ITU-T E.166/X.122 (1998), Numbering plan interworking for E.164 and X.121 numbering plans. 3 ITU-T I.112 (1993), Vocabulary of
26、terms for ISDNs. 4 ITU-T I.113 (1997), Vocabulary of terms for broadband aspects of ISDNs. 5 ITU-T X.1 (2000), International user classes of service in, and categories of access to, public data networks and integrated services digital networks (ISDNs). 6 ITU-T X.25 (1996), Interface between data ter
27、minal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit. 7 ITU-T X.36 (2000), Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) public data netw
28、orks providing frame relay data transmission service by dedicated circuit. 8 ITU-T X.75 (1996), Packet-switched signalling system between public networks providing data transmission services. 2 ITU-T X.371/Y.1402 (02/2001) 9 ITU-T X.76 (2000), Network-to-network interface between public networks pro
29、viding PVC and/or SVC frame relay data transmission service. 10 ITU-T X.115 (1995), Definition of address translation capability in public data networks. 11 ITU-T X.115 (1995)/Amd.1 (1996), Definition of address translation capability in public data networks Refinements. 12 ITU-T X.116 (1996), Addre
30、ss translation registration and resolution protocol. 13 ITU-T X.121 (2000), International numbering plan for public data networks. 14 ITU-T X.200 (1994), Information technology Open Systems Interconnection Basic reference model: The basic model. 15 ITU-T X.213 (1995), Information technology Open Sys
31、tems Interconnection Network service definition. 16 ITU-T X.300 (1996), General principles for interworking between public networks and between public networks and other networks for the provision of data transmission services. 17 ITU-T RFC IETF 793 (1981), Transmission Control Protocol. 18 ITU-T RF
32、C IETF 2865 (2000), Remote Authentication Dial In User Service (RADIUS). 19 ITU-T RFC IETF 2866 (2000), RADIUS Accounting. 3 Terms and definitions In addition to the terms and definitions contained in ITU-T I.112, ITU-T I.113, ITU-T X.200 and ITU-T X.300, the following term is defined: 3.1 Encapsula
33、tion: Occurs when the conversions in the network or in the terminals are such that the protocols used to provide one service make use of the layer service provided by another protocol. This means that at the interworking point, the two protocols are stacked. When encapsulation is performed by the te
34、rminal, this scenario is also called interworking by port access (see 3.2.11/X.300). 4 Abbreviations This Recommendation uses the following abbreviations: ARE Address Resolution Entity AU Access Unit DTE Data Terminal Equipment ET Exchange Termination FRPDN Frame Relay Public Data Networks IP-TE Int
35、ernet Terminal Equipment IWF InterWorking Function PSPDN Packet Switched Public Data Networks PVC Permanent Virtual Circuit ITU-T X.371/Y.1402 (02/2001) 3 QOS Quality Of Service SVC Switched Virtual Circuit TCP Transmission Control Protocol VC Virtual Call 5 Conventions No particular conventions are
36、 included. 6 Interworking between the Internet and PSPDNs 6.1 General arrangements for the access cases 6.1.1 Reference configuration Reference configuration for the access cases is shown in Figure 6-1. In this case, Adapter and AU provide encapsulation function specified in ITU-T X.37. Encapsulatio
37、n of IP packets is only provided to convey IP packets through the PSPDN. PSPDN may provide PVCs or VCs. In addition, Address Resolution Entity as specified in ITU-T X.115 and ITU-T X.116 may be equipped within the PSPDN to provide the Adapter and the AU with routing information. In this configuratio
38、n, IP packets are transparently exchanged between the IP-TE and the Internet. Use of PVCs or VCs are not visible to the IP-TE and the Internet. The Adapter and the ARE may reside within the PSPDN, or may be outside the PSPDN. NOTE ITU-T X.115 and/or ITU-T X.116 may need enhancement for the purpose o
39、f this Recommendation. T0733510-00AUX.25IP-TEInternetAdapterAREPSPDNFigure 6-1/X.371/Y.1402 Reference configuration for interworking between the Internet and PSPDN (access case) 6.1.2 IP packet handling In case PVCs are provided through the PSPDN, the Adapter and the AU perform the following functio
40、ns: i) When the Adapter receives IP packets from the IP-TE, it shall transmit them onto the pre-established PVCs, and vice versa. ii) When the AU receives IP packets from the PVC(s), it shall transmit them to a pre-assigned Internet port, and vice versa. 4 ITU-T X.371/Y.1402 (02/2001) In case VCs ar
41、e provided through the PSPDN, the Adapter and the AU perform the following functions: i) When the Adapter receives IP packets from the IP-TE, it shall check if a VC has been already established toward the AU. If a VC has been established, the Adapter sends the received IP packets onto the VC. If no
42、VC has been established, the Adapter shall set up a VC using the procedures as specified in ITU-T X.25. And then, the Adapter sends the received IP packets onto the established VC. The Adapter may clear the VC if it receives no IP packets from the IP-TE or from the AU during a certain amount of time
43、. ii) When the AU receives IP packets from the Internet, it shall perform similar functions as stated in the previous paragraph. In the above cases, the IP-TE subscribes to the PSPDN, and an AU is assigned for the IP-TE on subscription. There are also another case where different AUs or the IP-TEs a
44、re dynamically selected depending on the destination IP addresses. In this case, the Adapter and the AU perform the following functions: i) The Adapter acquires a mapping relationship between the destination IP addresses received from the IP-TE and X.121 numbers allocated to the AUs using the proced
45、ures defined in 6.1.3. When the Adapter receives IP packets from the IP-TE, it shall check the destination address of the IP and derived X.121 addresses of the corresponding AUs from the destination IP address, and then transmit them towards the AUs according to the procedures for the PVC and VC cas
46、es described above. ii) The AU acquires a mapping relationship between the destination IP addresses received from the Internet and X.121 numbers allocated to the ports of the IP-TEs using the procedures defined in 6.1.3. In this case, the IP-TE may or may not subscribe to the PSPDN. In case the IP-T
47、E subscribes to the PSPDN, authentication, authorization and accounting functions (as specified in IETF RFC 2865 and RFC 2866) shall be performed by the ARE. In case the IP-TE does not subscribe to the PSPDN, there shall be a contract between service providers of the PSPDN and that of the Internet.
48、6.1.3 ARE procedures There are two kinds of procedures related to the ARE functions: a) registration procedures; b) inquiry and response procedures. Registration procedures enable the ARE to get information about mapping between IP addresses and X.121 addresses from the Adapter or the AU according t
49、o the following mechanisms: i) The Adapter and the AU have normal router functions of the Internet and perform as routers outside the PSPDN. Therefore, the Adapter and the AU can route IP packets towards the IP-TE and the Internet, respectively. In addition, the Adapter and the AU have information related to X.121 numbers allocated to the IP-TEs and the AUs. ii) The Adapter and the AU periodically communicate with the ARE to inform it of updated information about mapping between X.121 numbers and
