1、 - STD-ITU-T RECMN X.3bL-ENGL L77b 48b259L Ob27791 TT7 INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUN KATION STANDARDIZATION SECTOR OF ITU X.361 (1 0196) SERIES X: DATA NETWORKS AND OPEN SYSTEM CO M M U N I CAT I O N Interworking between networks - Satellite data t ra nsm iss ion systems Co
2、nnection of VSAT systems with Packet-Switched Public Data Networks based on X.25 procedures ITU-T Recommendation X.361 (Previously CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION PUBLIC DATA NETWORKS Services and facilities Interfaces Transmission, si
3、gnalling and switching Network aspects Maintenance Administrative arrangements OPEN SYSTEM INTERCONNECTION Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specifications PICS proformas Protocol Identification Security Protocols Layer Manage
4、d Objects Conformance testing INTERWORKING BETWEEN NETWORKS General 11 Sateiite ata transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN.l) OS1 MANAGEMENT Systems Manageme
5、nt framework and architecture Management Communication Service and Protocol Structure of Management Information Management functions SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING X.1-X.199 X.1-X.19 X.20-X.49 X.50-X
6、.89 X.90-X. 149 X.150-X. 179 X. 180-X. 199 X.200-X.299 X.200-X.209 X.210-X.219 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.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.7
7、10-X.7 19 X.720-X.729 X.730-X.799 X.800-X. 849 X. 850-X . 899 X.850-X.859 X.860-X.879 X.880-X.899 X.900-X.999 For further details, please refer to ITU-T List of Recommendations. - STDOITU-T RECMN X-3bL-ENGL L77b m 9b257L Ub27773 871 FOREWORD The ITU-T (Telecommunication Standardization Sector) is a
8、permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for 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
9、Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsi
10、nki, March 1-12, 1993). ITU-T Recommendation X.361 was prepared by ITU-T Study Group 7 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 5th of October 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommun
11、ication administration and a recognized operating agency. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recornmendation
12、 X.361 (10/96) i CONTENTS Scope References Abbreviations . Interconnection scenarios . 4.1 General 4.2 Definitions 4.3 Interconnection scenarios . Interface requirements 5.1 Layer 1 5.2 Layer 2 5.3 Layer 3 5.4 5.5 Addressing information 5.6 Facilities information OS1 network layer service Annex A .
13、Connection quality guidelines . A.l General A.2 Base for the definition of the VSAT performance parameters . A.3 Delay performance A.4 Throughput performance A.5 Accuracy and dependability performance A.6 Availability performance 11 Recommendation X.361 (10/96) Page 1 1 2 2 2 3 3 5 6 6 6 7 7 8 9 9 9
14、 10 16 17 17 SUMMARY This Recommendation applies to private network implementations of VSAT systems. It describes their interconnection to PSPDNs via the X.25 protocol together with specifications for Quality of Service (QOS) levels compatible with the X. 130-Series performance Recommendations on X.
15、25E.75 packet-switched performance. . Recommendation X.361 (10/96) 111 STDaITU-T RECMN X-3bL-ENGL L99b m 48b259L b27777 Y17 W Recommendation X.361 CONNECTION OF VSAT SYSTEMS WITH PACKET-SWITCHED PUBLIC DATA NETWORKS BASED ON X.25 PROCEDURES (Geneva, 1996) 1 Scope This Recommendation describes the re
16、quirements for interconnecting a VSAT system operating as a Private Data Network (PvtDN) to a Packet-Switched Public Data Network for provision of the Data Transmission Service as defined in clause 3/Recommendation X.2. VSAT systems may also be connected to Packet-Switched Public Data Networks using
17、 other scenarios. The interconnections under such scenarios are not covered by this Recommendation. 2 References The following Recommendations, and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the
18、 editions indicated were valid. All Recommendations and other references are subject to revision; all 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 curre
19、ntly valid ITU-T Recommendations is regularly published. - IT-T Recommendation X.2 (1 996), International data transmission services and optional user facilities in public data networks and ISDNs. - ITU-T Recommendation X.25 (1996), Interface between Data Terminal Equipment (DTE) and Data Circuit-te
20、rminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit. - ITU-T Recommendation X.32 (1996), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode
21、 and accessing a Packet Switched Public Data Network through a Public Switched Telephone Network or an Integrated Services Digital Network or a Circuit Switched Public Data Network. - ITU-T Recommendation X.35 (1993), Interface between a PSPDN and aprivate PSDN which is based on X.25 procedures and
22、enhancements to define a gateway function that is provided in the PSPDN. - ITU-T Recommendation X. 121 (1996), International numberingplan for public data networks. - CCITT Recommendation X.134 (1992), Portion boundaries and packet layer reference events: basis for defining packet-switched performan
23、ce parameters. - CCITT Recommendation X. 135 (1992), Speed of service (delay and throughput) performance valuesfor public data networks when providing international packet-switched services. - CCITT Recommendation X. 136 (1992), Accuracy and dependability performance values for public data networks
24、when providing international packet-switched services. - CCITT Recommendation X.137 (1992), Availability performance values for public data networks when providing international packet-s witched services. Recommendation X.361 (10/96) 1 STDaITU-T RECMN X.3bl-ENGL 177b m 48b2.571 Ob27776 353 W - CCITT
25、 Recommendation X.138 (1992), Measurement of performance values for public data networks when providing international packet-switched services. CCITT Recommendation X.139 (1992), Echo, drop, generator and test DTEs for measurement of performance values in public data networks when providing internat
26、ional packet-switched services. IT-T Recommendation X.213 (1995) I ISOAEC 8348:1996, Information technology - Open Systems Interconnection - Network service definition. ITU-T Recommendation X.223 (1993), Use ofX.25 to provide the OSI connection-mode network service for ITU-T applications. ITU-T Reco
27、mmendation X.327 (1 993), General arrangements for interworking between Packet Switched Public Data Networks (PSPDNs) and private data networks for the provision of data transmission services. - - - - 3 Abbreviations For the purposes of this Recommendation, the following abbreviations are used: BCD
28、DCE DM DNIC DTE FCS FRMR ISDN LAPB NTN os1 PNIC PSDN PSPDN PVC PvtDN SABM VSAT Binary Coded Decimal Data Circuit-terminating Equipment Disconnect Mode Data Network Identification Code Data Terminal Equipment Frame Checking Sequence Frame Reject Mode Response Integrated Services Digital Network Link
29、Access Procedure Balanced Network Terminal Number Open Systems Interconnection Private Network Identification Code Packet-Switched Data Network Packet-Switched miblic Data Network Permanent Virtual Circuit Private Data Network Set Asynchronous Balanced Mode Very Small Aperture Terminal (Terminai com
30、municating via satellite with a very small aperture antenna) 4 Interconnection scenarios 4.1 General A VSAT system is considered as a particular form of implementation of a Private Data Network (PvtDN). This type of PvtDN is a specific type of network covered by Recommendation X.327. A VSAT DTE conn
31、ected to the PSPDN shall appear to the PSPDN as a normal X.25 DTE. The PSPDN makes no allowance for, and has no knowledge of, the VSAT system. The set of all the elements of a VSAT system which constitute this PvtDN is called hereafter the VSAT network. 2 Recommendation X.361 (10/96) STD-ITU-T RECMN
32、 X.3bL-ENGL 177b LiBb257L Ob27797 27T D 4.2 Definitions The following elements are identified in the connection and are shown in Figures 1 and 2: I l A this Recommendation. The applications (A) dialogue with each other by means of end-to-end protocols which are outside the scope of B The application
33、 running at the DTE (B) must implement a local interface to the remote VSAT (D). This interface is not subject to standardization. However, the guidelines related to connection quality defined in Annex A are based on the assumption that this interface satisfies Recommendation X.25. C The remote VSAT
34、 provides an appropriate interface (C). D The remote VSAT station (D) provides the communication over the satellite. The way in which this is done and the internal protocols of the VSAT network are outside the scope of this Recommendation. The layers 2 and 3 over the satellite links may be different
35、 from those at the PSPDN interface and at the DTE-B interface. E VSATs communicate. The HUB station (E), in the case of a star network. This HUB is the central station with which all the remote NOTE -Elements (D) and (E) may reside in the same physical equipment. F may be implemented at either the H
36、UB or at any of the remote VSAT stations. The interface between the VSAT network and the PSPDN. This is a DTE (F) on the VSAT network side and G occur on the interface to the VSAT network and also on the interface to the customer connected to the PSPDN. The PSPDN DCEs. These are customer connection
37、points which offer an X.25 interface to the PSPDN. These H This is a generic PSPDN which may be made up of a number of national and possibly international portions. These portions are defined in Recommendation X.134 and their quality of service is defined in Recommen- dations X.135, X.136 and X.137,
38、 which provide worst case values. I The remote DTE (I) of the customer connected to the PSPDN where the corresponding application runs. J The store-and-forward gateway between the VSAT network and the PSPDN. This element takes the responsibility of delivering the messages received from either the re
39、mote DTE (B), or the remote DTE (I), to its counterpart. 4.3 Interconnection scenarios Within the VSAT network it is possible to conceive two forms of connection (see Figures 1 and 2). 4.3.1 Real-time direct connection In this scenario a real-time connection is established between the application se
40、rved by one of the VSAT stations and the application served by a DTE connected to the PSPDN. The Switched Virtual Circuit (SVC) or the Permanent Virtual Circuit (PVC) over the PSPDN is extended over the VSAT network. Two types of connection over the VSAT network are considered (see Figure 1): - sing
41、le hop connections which apply in mesh networks, i.e. those that allow the direct communication between remote VSATs, and on star networks in which the interface to the PSPDN is implemented exclusively at the HUB; the following two paths are identified in Figure 1: A2+B+C+D 1 +S+D2+F2+G3+G4+12+A3 A2
42、+B+C+Dl+S+D3+E+Fl +Gl+G2+11 +Al - double hop connections which apply in star VSAT networks which implement the DTE interface to the PSPDN at a remote VSAT. In these cases all communications are routed via the HUB and therefore require two satellite hops; the following path is identified in Figure 1:
43、 A2+B+C+D 1 +S+D3 +E+D3+S-+D2+F2+G3+G442+A3 Recommendation X.361 (10196) 3 STD-ITU-T RECMN X.3bL-ENGL L99b m 48b2591 b27800 831 D1 VSAT I k Rl RZ VS Tnetwork .Il rp . R, R, Bit rate at DTE (B)-DCE (C) interface Bit rate at DTE (F)-DCE (G) interface FIGURE 1X.361 Real-time direct connection scenario
44、4.3.2 Store-and-forward This scenario is depicted in Figure 2. In this scenario the delivery to/from the remote DTE (B) is performed over the VSAT network to a store-and-forward gateway (J) connected to the PSPDN via a DTE (F). The delivery frondto the remote DTE (I) takes place from the gateway ove
45、r the PSPDN as a separate transaction. This means there is no real-time interaction between the remote DTE (B) and the remote DTE (I). The gateway function may incorporate protocol conversion at either low functional layers or high functional layers. Such conversion is outside the scope of this Reco
46、mmendation. From the PSPDN point of view the connection is performed with the applications residing in the gateway. As such, the services offered by the PSPDN and their quality of service is in no way affected by the VSAT network. For the PSPDN, the DTE (F) to which the store-and-forward gateway is
47、connected shall introduce no special requirements for addressing purposes. This function of the store-and-forward gateway is considered part of the user defined protocols and is therefore outside the scope of this Recommendation. 4 Recommendation X.361 (10196) STD-ITU-T RECMN X.3bL-ENGL 199b m Li8b2
48、59L Ob2780L 778 B - DTE i DTE I DI VSAT I I - I 4 k . Rl VSAT network (H) PSPDN T072606M6Id02 FIGURE 2K.361 Store-and-forward gateway scenario 5 Interface requirements The interface R provided by a VSAT network to be connected to a PSPDN shall comply with Recommendation X.25 for dedicated access or
49、Recommendation X.32 for switched access. NOTE 1 - Appendix VK.25 provides guidelines for the appropriate selection of parameter settings on the X.25 link in order to maximize the efficiency of the link when the transmission is over channels with long round trip delay (satellite circuits). NOTE 2 - To allow for terminals on the VSAT network to be addressed by DTEs on the PSPDN, numbering of VSAT DTEs should be in accordance with Recommendation X.121. Annex BK.121 gives guidance on the use of Private Network Identification Codes to ailow for the numbering
