1、ITU-T RECMN*H-322 96 = 4862591 0637882 T79 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU H.322 (03196) TRANSMISSION OF NON-TELEPHONE SIGNALS VISUAL TELEPHONE SYSTEMS AND TERMINAL EQUIPMENT FOR LOCAL AREA NETWORKS WHICH PROVIDE A GUARANTEED QUALITY OF SER
2、VICE ITU-T Recommendation H.322 (Previously “CCIlT Recommendation”) ITU-T RECMN*H*322 96 4862593 ObL7B83 905 M FOREWORD The IT-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The IT-T is responsible for studying technical, operati
3、ng and tanff 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 -T Study Groups which, in their turn
4、, 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 (Helsinki, March 1-12, 1993). IT-T Recommendation H.322 was prepared by ITU-T Study Group 15 (1993-1996) and was approved under the WT
5、SC Resolution No. 1 procedure on thel9th of March 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITIJ 1996 All rights reserved. No part of this publication may be repr
6、oduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. ITU-T RECMN*H-322 76 4862573 Ob37884 841 CONTENTS 1 Scope 2 References 3 Definitions and abbreviations . 3.1 Definitions 3.2 Abbreviations 4 Ter
7、minai equipment . 5 H.322 gateway 6 Dependency on Recommendation H.320 . Page 1 3 3 3 4 4 5 6 Recommendation H.322 (03/96) i ITU-T RECMN*H-322 96 4862591 Ob37885 788 SUMMARY This Recommendation covers the technical requirements for narrow-band visuai telephone services defined in H.2WAV. 120-series
8、Recommendations, in those situations where the transmission path includes one or more Local Area Networks (LAN), each of which is configured and managed to provide a guaranteed Quality of Service (QOS) equivalent to that of N-ISDN such that no additional protection or recovery mechanisms beyond thos
9、e mandated by Recommendation H.320 need be provided in the terminais. It is noted that projected Recommendation H.323 addresses the use of some other LANs which are unable to provide the underlying performance assumed by this Recommendation. ii Recommendation H.322 (03/96) ITU-T RECMN*H-322 96 48625
10、91 0617886 bL4 Recommendation H.322 VISUAL TELEPHONE SYSTEMS AND TERMINAL EQUIPMENT FOR LOCAL AREA NETWORKS WHICH PROVIDE A GUARANTEED QUALITY OF SERVICE (Geneva 1996) The ITU-T, considering the widespread adoption of and the increasing use of the H.320 Recommendation for videophony and videoconfere
11、ncing services over networks conforming to the N-ISDN characteristics specified in the I-Series Recommendations, appreciating the desirability and benefits of enabling the above services to be carried, wholly or in part, over Local Area Networks while also maintaining the capability of interworking
12、with H.320 terminals, and noting the characteristics and performances of the many types of Local Area Network which are of potential interest, recommends that systems and equipment meeting the requirements of the H.322 or H.323 Recommendations are utilized to provide these facilities. 1 Scope This R
13、ecommendation covers the technical requirements for narrow-band visual telephone services defined in H.200/AV. 120-Series Recommendations, in those situations where the transmission path includes one or more Local Area Networks (LAN), each of which is configured and managed to provide a guaranteed Q
14、uality of Service (QOS) equivalent to that of N-ISDN such that no additional protection or recovery mechanisms beyond those mandated by Recommendation H.320 need be provided in the terminals. Pertinent parameters are the data error and loss properties and variation of transit delay this Recommendati
15、on also requires that the ISDN clock is available at the terminals. An example of a suitable LAN is: IEEE Std 802.9a-1995, EEE Standard for Local and Metropolitan Area Networks - Supplement to Integrated Services (IS) LAN Interface at the Medium Access Control (MAC) and Physical (PHY) Layers: Specif
16、ication of ISLAN16-T. Recommendation H.323 addresses the use of some other LANs which are unable to provide the underlying performance assumed by this Recommendation. Although some LANs offer satisfactory QOS to support this Recommendation, they do not themselves provide standardized means of identi
17、fying the intended called terminal. For such LANs the procedures for terminal addressing defined in Recommendation H.323 shall apply in addition to the provisions of this Recommendation. This Recommendation does not encompass ATM LANs because they are within the scope of Recommendation H.321. System
18、s and terminal equipment complying with this Recommendation are able to interwork with each other and with those complying with Recommendations H.320, H.321 and H.323. The concept is shown in Figure 1 in which any terminal can be connected to any other. The H.322 gateway unit provides an interconnec
19、tion between the LAN and the Wide Area Network (WAN) which may be N-ISDN or B-ISDN or both. An H.322 terminai communicates with another H.322 terminal on the same LAN directly. The gateway may be connected via N-ISDN or B-ISDN to other gateways and LANs to provide communication between H.322 or H.32
20、3 terminals which are not on the same LAN. Although this Recommendation specifically addresses visual telephone systems, the methods used do not depend on the content of the signals carried. Consequently this Recommendation has more general applicability to connecting terminals, originally designed
21、for N-ISDN, over LAN or hybrid LAN and ISDN networks. Recommendation H.322 (03/96) 1 ITU-T RECMN*H-322 96 4862593 Ob37887 550 H.3P Terminal .-. RW.H.322 T1518850-95/d01 _- -_._.- -_ -_ H .323 Gateway NOTE - A gateway may support only the N-ISDN or B-ISDN connection. H.323 . . RW.H.323 Terminal FIGUR
22、E 1H.322 Scope and interworking capabilities of Recommendation H.322 H.323 Terminal 2 Recommendation H.322 (03/96) H.323 H.323 Terminal Terminai ITU-T RECMN*H*322 96 9 4862591 0617888 497 = 2 References The following Recommendations and other references contain provisions which, through reference in
23、 this text, constitute provisions of this Recommendation. At the time of publication, the 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 rec
24、ent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - - Recommendation E.164 (1991), Numbering plan for the ZSDN era (same as Recommendation 1,331). ITU-T Recommendation H.221 (1995). Frame structure for a
25、64 to 1920 kbius channel in audiovisual teleservices. - ITU-T Recommendation H.230 (1993, Frame-synchronous control and indication signals for audiovisual systems. -T Recommendation H.23 1 (1996), Multipoint control units for audio-visual systems using digital channels up to 1920 kbitls. -T Recommen
26、dation H.242 (1996). System for establishing communication between audiovisual terminas using digital channels up to 2 Mbit/s. ITU-T Recommendation H.261 (1996), Video codee for audiovisual services atp x 64 kbitls. -T Recommendation H.320 (1996), Narrow-band visual telephone systems and terminal eq
27、uipment. ITIJ-T Recommendation H.321 (1996), Adaptation of H.320 visual telephone terminals to B-ISDN environments. IT-T Recommendation H.323l), Visual telephone systems and terminal equipment for local area networks which provide a guaranteed quality of service. ITU-T Recommendation H.33 1 (1993),
28、Broadcasting type audiovisual mulripoint systems and terminal equipment. ITU-T Recommendation 1.430 (1993, Basic user-network intelface - Layer I specification. ITU-T Recommendation 1.43 1 (1993), Primary rate user-network inte$ace - Layer I specification. ITU-T Recommendation 1.432 (1993). B-ISDN u
29、ser-network intelface - Physical layer specification. ITU-T Recommendation 1.580 (1995). General arrangements for interworking between B-ISDN and 64 kbius based ISDN. - - - - - - - - - - - 3 Definitions and abbreviations 3.1 Definitions For the purposes of this Recommendation, the following definiti
30、ons apply. 3.1.1 local area network (LAN): A shared or switched medium peer-to-peer communications network that broadcasts information for ail stations to receive within a moderate-sized geographic area, such as a single office building or a campus. The network is generally owned, used and operated
31、by a single organization. It provides services including those of the physical layer, the MAC layer, and the transport layer. 3.1.2 accommodates terminals and LANs. It may typically be an N-ISDN or a B-ISDN. wide area network (WAN): A communication network which covers a wide geographical area and P
32、resently at the stage of draft. Recommendation H.322 (03/96) 3 3.2 Abbreviations For the purposes of this Recommendation, the following abbreviations are used: ATM B-ISDN CSMNCD LAN MAC MCU N-ISDN QOS WAN Asynchronous Transfer Mode Broadband ISDN Carrier sense multiple access with collision detectio
33、n Local Area Network Media access control Multipoint control unit Narrow-band Integrated Services Digital Network Quality of Service Wide Area Network 4 Terminal equipment Figure 2 is a block diagram of the H.322 terminal. All elements are identical to those specified in Recommen- dation H.320 excep
34、t for the LAN interface. Recommendation H.261 Recommendation H.221 I 1 I 1 I video codec Video WO equipment H.2WAV.25Xeries Recommendations I Delay Audio codec Mud Audio WO equipment I Demux T-series, H.20WAV.270-Series Recommendations, etc. I I H Telematic equipment I Recommendations H.242, H.230,
35、H.221 I Encl-bend cigialiing C&i I system I Cntroi Encl-to-network signalling Recommendation H.322 Terminal equipment FIGURE 2H.322 Block diagram of R322 terminai elemens Data formatting and Local Area Network Interface . . . . . . . . T15188695/d02 4 Recommendation H.322 (03/96) ITU-T RECMN*H-322 7
36、6 = 4862571 0617890 045 W As illustrated in Figure 3, an H.322 terminal may be implemented as an integrated unit or as the combination of an H.320 terminai and an adapter unit. I Terminai H.322 YUN - H.322 Terminai . !“HFli I Terminai . T151 870-9Yd3 FIGURE 3M.322 Aiternative H322 terminal implement
37、ations NOTE - The Adapter Unit of Figure 3 and the H.322 Gateway of Figure 1 perform no function which is specific to the audiovisual nature of the signais they handle. The same Adapter Unit and Gateway may support the connection of other N-ISDN terminals in place of the H.320 terminai in Figure 3,
38、but such use is outside the scope of this Recommendation. 5 H.322 gateway Some LANs have a star topology in which the central hub may be connected to the WAN as a normal feature. In such circumstances, for example BEE 802.9a LANs, the H.322 gateway is the central hub. For other LANs the H.322 gatewa
39、y may be an additional device connecting the LAN to the WAN. This is the case shown in Figure 1. A block diagram of the H.322 gateway device is shown in Figure 4. There are four principal functions: - Interface to the LAN. - Interface to the WAN (Recommendation 1.430 or 1.431 for N-ISDN or Recommend
40、ation 1.432 for B-ISDN). - Conversion of the destination address of the called H.322 terminal. This is required only if the LAN does not support Recommendation E. 164. - Interworking Adapter if the WAN is B-ISDN. The basic functions required are essentially those specified in Recommendation 1.580 fo
41、r interworking between N-ISDN and B-ISDN. The number of simultaneous connections which the H.322 gateway is able to provide is not subject to standardization. An H.322 gateway may also contain the functionality of a Multipoint Control Unit (MCU) as specified in Recommendation H.23 1. This is not a m
42、andatory requirement of this Recommendation. An H.322 gateway may also contain the functionality specified in Recommendation H.33 1 to simultaneously broadcast to a number of terminals. This is not a mandatory requirement of this Recommendation. Recornmenda tion H.322 (03/96) 5 ITU-T RECMN*H1322 96
43、m 4862573 Ob17891 T81 m w Rec. 1.430 Rec. 1.431 or or Rec. 1.432 - N-ISDN or B-ISDN Interface .-I t- Intenivorking Adaptor (Note 1) LAN Interface _, LAN - Destination Address Converter (Note 2) I I TI 51 8880-95Id04 NOTES 1 2 Not present in some gateways. Required only if LAN does not directly suppo
44、rt Recommendation E. 164. FIGURE 4M.322 Block diagram of H.322 gateway elements 6 Dependency on Recommendation H.320 All the provisions of all clauses subsequent to and including subclause 3.2 of Recommendation H.320 are an integral part of this Recommendation. 6 Recommendation H.322 (03/96) ITU-T RECMN*H-322 96 48b2591 Ob17892 918 Imprim en Suisse Genve, 1996
