Multimedia & Communication Lab. T.120 : Data Protocol for Multimedia Conferencing Advanced multimedia 4/27/1999 Jeong, Hwanseok [email protected]

Multimedia & Communication

Lab.

T.120 : Data Protocol for Multimedia Conferencing

Advanced multimedia

4/27/1999

Jeong, Hwanseok

[email protected]


Lab.

Contents

Overview Normative references Introduction to Multimedia Communication The T.120 System Model T.120 Infrastructure Recommendation Application Protocol Recommendation T.120 Compliance References


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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 a

nd 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 Annotat

ion Protocol ITU-T Recommendation T.127(1995), Multipoint Binary File Transfer Pr

otocol


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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


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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 se

rvice, 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


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Introduction to Multipoint Multimedia Communication(cont’d)

Terminal Terminal

TerminalMultiportterminal

Multiportterminal 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 >


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< Multipoint topology-3 MCUs providing connection to allow multipleterminal to participate in a conference >

MCU

MCU MCU

Terminal Terminal Terminal Terminal

Terminal

Terminal


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MCU MCU

Terminal Terminal

Terminal

TerminalTerminal

TerminalTerminal

Terminal

LAN Gateway-Router-

Terminal Terminal Terminal

LAN Gateway-Router-

Corporate Network A

Corporate Network B

PSTN

ISDN

PSTN

PSTN

ISDNISDN

ISDN

Public Network

< < Example of a mixed-network conference topology >


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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 ApplicationProtocol Recommendation

User Application(s)(Using Std. App. Protocol)

…Non-Std. App.Protocol Entity

ITU-T T.120 Infrastructure Recommendatios


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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 s

ervices by GCC and MCS T.121(Generic Application Template) provide on how to utilize th

e T.120 infrastructure in a consistent way


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T.120 System Model(cont’d)

Application Protocols Protocol Data Units(PDUs) + actions for App. peer-to-peer commun

ication 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 Servi

ce Element) ARM : generic functionality relevant to all protocols ASE : application specific functionality Both of these are described in T.121(Generic App. Template)


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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 commun

ication 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


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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


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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

T.125 - Multipoint Communications Service(MCS)

ISDNTransport

NetworkIndependent

Layer

NetworkDependent

Layer

CSDNTransport

PSDNTransport

PSTNTransport

B-ISDNTransport

NLANTransport


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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 la

yer below it and combine to form a multipoint domain MCS Provider(Top Provider) acting as the resource server f

or 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


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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 i

n a conference


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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


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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)


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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


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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


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T.127 : Multipoint Binary File Transfer(MBFT)

MBFT MBFT MBFT

MCSProvider

MCSProvider

MCSProvider

Top MCSProvider

Node that require file A

Node that requirefiles A and B

Control channel

Data channel


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Non-Standard Application Protocols

Must use GCC in a way that does not risk conflict with other app. protocol entity


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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

T.121

T.123

T.124

T.125

T.126

T.127

conditional

mandatory

mandatory

mandatory

conditional

conditional

Depend on condition

Depend on condition

Depend on condition

Depend on condition


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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/

Documents

Multimedia & Communication Lab. T.120 : Data Protocol for Multimedia Conferencing Advanced multimedia 4/27/1999 Jeong, Hwanseok [email protected]