ITU-T Recommendation H.321

Title: Adaptation of H.320 visual telephone terminals to B-ISDN environments

Date of adoption : 02/1998

Summary

This Recommendation describes technical specifications for adapting narrow-band audiovisual communications terminals, as defined in Recommendation H.320, to broadband ISDN environments. The terminal conforming to this Recommendation interworks with the same type of terminals (i.e. other H.321 terminals) accommodated in B-ISDN as well as existing H.320 terminals accommodated in N-ISDN. This revision defines an AAL-5 based stack in addition to the AAL-1 based stack.

TABLE OF CONTENTS

    Page
1 Scope 1
2 References 1
3 Definitions and abbreviations 2
3.1 Definitions 2
3.2 Abbreviations 3
4 System description 4
4.1 Applications 4
4.2 System configuration 4
4.3 Generic terminal architecture 4
4.4 Terminal type 5
4.5 Point-to-point communication 5
4.6 Multipoint communication 6
5 Infrastructure 6
5.1 Audio coding 6
5.2 Video coding 6
5.3 Multimedia multiplexing and synchronization 6
5.4 End-to-end control 6
5.5 Communication procedures 7
5.6 AAL functions 7
5.7 Call control 8
5.8 Synchronization of 8 kHz timing 8
5.9 ATM Transfer Capability 8
6 Terminal equipment 8
6.1 Audio source and arrangement 8
6.2 Video source and arrangement 8
6.3 Data and other auxiliary equipment 8
6.4 Optional enhancements 8
6.5 Error resilience 8
7 Intercommunications 8
7.1 Intercommunication among H.321 terminals 9
7.2 Intercommunication with N-ISDN terminals 9
7.2.1 Intercommunication with H.320 9
7.2.2 Intercommunication with telephony 10
7.3 Intercommunication between AAL-1 and AAL-5 10
7.4 Intercommunication with audiovisual terminals connected to other networks 11
Annex A The use of ATM Adaptation Layer Type 1 11
A.1 Scope 11
A.2 AAL functions 11
A.2.1 Convergence sublayer functions 11
A.2.2 SAR sublayer functions 12
A.2.3 Cell Delay Variation 12
A.3 Call control 12
A.3.1 Digital connection 12
A.3.2 Telephony connection 15
Annex B The use of ATM Adaptation Layer Type 5 16
B.1 Scope 16
B.2 Terminal architecture 17
B.3 Network Adaptation Layer 17
B.3.1 Alignment of octets 18
B.3.2 Interleaving of time slots 18
B.3.3 Determination of packet size 18
B.3.4 Optional error handling procedures 18
B.4 AAL functions 19
B.4.1 Convergence sublayer functions 19
B.4.2 SAR sublayer functions 19
B.5 Call control 19
B.5.1 Digital connection 19
B.5.2 Telephony connection 21
Annex C Alternatives for 8 kHz timing of H.321 terminals 23
C.1 Scope 23
C.2 Receiver clock 23
C.3 Transmitter clock 23
C.4 Choosing between adaptive and independent clocks 24