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T.120 : Data Protocol for Multimedia Conferencing

T.120 : Data Protocol for Multimedia Conferencing

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T.120 : Data Protocol for Multimedia Conferencing

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

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

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

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

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

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

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

  8. Introduction to Multipoint Multimedia Communication(cont’d) Public Network Corporate Network A Terminal Terminal LAN Gateway -Router- ISDN ISDN Terminal Terminal Terminal ISDN MCU MCU PSTN ISDN Corporate Network B LAN Gateway -Router- Terminal PSTN Terminal Terminal Terminal Terminal Terminal PSTN < Example of a mixed-network conference topology > < Multimedia & Communication Lab.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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