ITU-T Recommendation H.321
Title: Adaptation of H.320 visual telephone terminals to B-ISDN environmentsDate 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 |