1. Multimedia & Communication Lab. T.120 : Data Protocol for Multimedia Conferencing Advanced multimedia 4/27/1999 Jeong, Hwanseok hsjeong@mmlab.snu.ac.kr

2. Multimedia & Communication Lab. Contents n Overview n Normative references n Introduction to Multimedia Communication n The T.120 System Model n T.120 Infrastructure Recommendation n Application Protocol Recommendation n T.120 Compliance n References

3. Multimedia & Communication Lab. Normative reference n ITU-T Recommendation T.121(1996), Generic Application Template n ITU-T Recommendation T.122(1993), Multipoint Communication Service for Audiographic and Audiovisual Conferencing service definition n ITU-T Recommendation T.123(1993), Protocol Stack for Audiographics and Audiovisual Teleconference Application n ITU-T Recommendation T.124(1995), Generic Conference Control n ITU-T Recommendation T.125(1994), Multipoint Communication Service Protocol n ITU-T Recommendation T.126(1995), Multipoint Still Image and Annotation Protocol n ITU-T Recommendation T.127(1995), Multipoint Binary File Transfer Protocol

4. Multimedia & Communication Lab. Overview n T.120 recommendation series : multipoint communication service for use in multimedia conferencing environments n T.120 m Introduction for the T.120 series, showing the inter-relationships between the constituent recommendation m requirements for compliance to T.120 for conferencing

5. Multimedia & Communication Lab. Introduction to Multipoint Multimedia Communication n Multipoint communication : interconnection of multiple terminals n MCU(Multiple Control Unit), or more simply a bridge, is required n T.120 series : the components providing both a data communications service, and a management service for any other media services present n MCU m nodes without terminal functionality, acting as bridging nodes, bridging data and other media streams present in the connections

6. Multimedia & Communication Lab. Introduction to Multipoint Multimedia Communication(cont’d) Terminal Multiport terminal Multiport terminal Terminal Point to point (The simplest case of a multipoint connection) Chain Connection with terminals acting as data bridges < Examples of Multipoint conference configurations showing various connection topologies and Node types >

7. Multimedia & Communication Lab. Introduction to Multipoint Multimedia Communication(cont’d) < Multipoint topology-3 MCUs providing connection to allow multiple terminal to participate in a conference > MCU Terminal

8. Multimedia & Communication Lab. Introduction to Multipoint Multimedia Communication(cont’d) MCU Terminal LAN Gateway -Router- Terminal LAN Gateway -Router- Corporate Network A Corporate Network B PSTN ISDN PSTN ISDN Public Network <

9. Multimedia & Communication Lab. T.120 System Model … User Application(s) (Using Both Standard and Non-standard Application Protocols User Application(s) (Using Non-std. Protocol) T.127 (MBFT) T.126(MSIA) Application Protocol Entity Generic Conference Control(GCC) T.124 Multipoint Communications Service(MCS) T.122/125 Network Specific Transport Protocols T.123 Node Controller ITU-T T.120 Application Protocol Recommendation User Application(s) (Using Std. App. Protocol) … Non-Std. App. Protocol Entity ITU-T T.120 Infrastructure Recommendatios

10. Multimedia & Communication Lab. T.120 System Model(cont’d) n Comprised of a communications infrastructure and the application protocols n User Application m use the services offered by the T.120 series m will generally be multipoint aware and designed to use the T.120 services by GCC and MCS m T.121(Generic Application Template) provide on how to utilize the T.120 infrastructure in a consistent way

11. Multimedia & Communication Lab. T.120 System Model(cont’d) n Application Protocols m Protocol Data Units(PDUs) + actions for App. peer-to-peer communication m The T.120 series includes application protocols designed to support multipoint conferencing m Application Protocol Entity 4 an instance of an Application Protocol 4 ARM(Application Resource Manager) + ASE(Application Service Element) 4 ARM : generic functionality relevant to all protocols 4 ASE : application specific functionality 4 Both of these are described in T.121(Generic App. Template)

12. Multimedia & Communication Lab. T.120 System Model(cont’d) n Node Controller m T.120 management role at a terminal or MCU m issue primitives to the GCC provider which starts and control the communication session : outside the scope of the T.120 n Communication Infrastructure m multipoint connectivity with reliable data delivery m Three components : GCC, MCS, Transport Protocol Profile n Networks m ISDN : Integrated Services Digital Nerwork m CSDN : switched or permanent digital circuits m PSDN : Packet Switched Data Network using X.25 m PSTN : Public Switched Telephone Network m B-ISDN, LAN under study

13. Multimedia & Communication Lab. T.120 Infrastructure Recommendation n Protocol Stacks for Audiographic and Audiovisual conferencing - T.123 n Multipoint Communication Service(MCS) - T.122, T.125 n Generic Conference Control (GCC) - T.124

14. Multimedia & Communication Lab. T.123 : Protocol Stacks for Audiographic and Audiovisual conferencing n Network specific transport stacks for each supported network n MCS takes the transport pairs from the layer below it and maps them into a multipoint domain T.125 - Multipoint Communications Service(MCS) ISDN Transport Network Independent Layer Network Dependent Layer CSDN Transport PSDN Transport PSTN Transport B-ISDN Transport NLAN Transport

15. Multimedia & Communication Lab. T.122, T.125 : Multipoint Communication Service(MCS) n T.122 : defines the MCS service n T.125 : specifies the data transmission protocol n MCS : multipoint “engine” of the T.120 conference n takes point-to-point transport connections provided by the layer below it and combine to form a multipoint domain n MCS Provider(Top Provider) acting as the resource server for the domain n MCS app direct data within domain via the use of channel n token are the last major facility provided by MCS m services are provided to grab, pass, inhibit, query token

16. Multimedia & Communication Lab. T.124: Generic Conference Control(GCC) n Comprehensive set of facilities for establishing and managing the multipoint conference n to maintain information about the nodes and applications that are in a conference n Applications create conferences, join conferences, and invite others to conference n conference security n capabilities for supporting the concepts of conductorship in a conference

17. Multimedia & Communication Lab. Application Protocol Recommendation n The Generic Application Template(GAT) - T.121 n Multipoint Still Image and Annotation Protocol(MSIA) - T.126 n Multipoint Binary File Transfer(MBFT) - T.127 n Non-Standard Application Protocols

18. Multimedia & Communication Lab. T.121 : The Generic Application Template(GAT) n A conceptual model of a T.120 application protocol n A guide to application protocol developers and user application developers on how to utilize the T.120 infrastructure to best effect n Two distinct parts m ARM(Application Resource Manager) + ASE(Application Service Element) m ARM : generic functionality relevant to all protocols m ASE : application-protocol-specific functionality m Both of these are described in T.121(Generic App. Template)

19. Multimedia & Communication Lab. T.126 : Multipoint Still Image and Annotation Protocol(MSIA) n To be used by a broad set of user application that require inter-operable graphical information exchange in a multi- vendor environment n white boarding, annotated image exchange, hard copy image exchange, remote computer application piloting, screen sharing n manage the conference-wide synchronization of multi- plane/multi-view graphical workspaces n Advanced option m keyboard and pointing device signaling

20. Multimedia & Communication Lab. T.127 : Multipoint Binary File Transfer(MBFT) n to support interchange of binary files within an interactive conferencing or group working environment n no restriction on the content of the files to be transferred n versatile n flexible n Optional advanced feature m Broadcast of multiple files simultaneously m Private distribution of files to a selected subset of the conference m Conductor control of file distribution

21. Multimedia & Communication Lab. T.127 : Multipoint Binary File Transfer(MBFT) MBFT MCS Provider MCS Provider MCS Provider Top MCS Provider Node that require file A Node that require files A and B Control channel Data channel

22. Multimedia & Communication Lab. Non-Standard Application Protocols n Must use GCC in a way that does not risk conflict with other app. protocol entity

23. Multimedia & Communication Lab. T.120 Compliance n transport Protocol stack profile(T.123) n multipoint Communication Service protocol(T.125) n mandatory parts of Generic Conference Control(T.124) n mandatory parts of any standardized app. Protocol T.121 T.123 T.124 T.125 T.126 T.127 conditional mandatory conditional Depend on condition

24. Multimedia & Communication Lab. References n ITU-T Recommendation T.120(1996), Data Protocol for Multimedia Conference. n “A Primer on the T.120 Series Standard”, http://www.databeam.com/ccts/