Global Multimedia Collaboration System

In order to build an integrated collaboration system over heterogeneous collaboration technologies, we propose a Global Multimedia Collaboration System (Global-MMCS) based on XGSP A/V Web-Services framework. This system can integrate multiple A/V services, and support various collaboration clients and communities. Now the prototype is being developed and deployed across many universities in USA and China.


Global-MMCS Architecture
To build an integrated large-scale multimedia collaboration system over heterogeneous network environments, we have to design a scalable computing architecture and a flexible software framework.Figure 1 shows such a solution to our Global-MMCS.The Messaging event services provide publish-subscribe paradigm for all kinds of group communications in collaboration applications.application.On top of these services, all the services can be described, implemented and deployed.

Global-MMCS Services
Videoconferencing services may include different collaboration systems, such as H.323, SIP [9] and AccessGrid [1] system.Real-Server will be added as

Web Services Architecture
The Session Web Service tries to provide a The community directories will be used to integrate different services from different communities.

Global MMCS Prototype & Implementation
We plan to build a Global-MMCS prototype system across the sites in US and China.In China, we have a partner group called Admire [2], also working on videoconferencing systems.Admire group comes from National Software Development Environment Lab of Beihang University.Now they are beginning to deploy the Admire videoconferencing system across the universities in China.Admire developers will build web-services of Admire system based on our framework.Indiana A/V research group will use these web-services interface to integrate Admire with H.323, SIP as well as Real Networks streaming systems.

Admire Project in China
Admire project has been started in 1999 and finished a prototype system -Admire.The initial aim of the early project was to develop a large scale real-time multimedia interaction environment on top of NSCFnet, which allows users distributed in different sites of NSCFnet to make distant seminars and scientific collaboration through multiple collaboration tools.Now, the prototype system can support various collaboration tools and provide a complete conference management as well as conference archiving service.Furthermore, it can be deployed on heterogeneous network environments, supporting both unicast and multicast communication.
By the end of 2002, Admire system has been deployed in over 20 sites in NSFCNET, CERNET China, and several sites in Japan and United States.
Admire system is also interoperable with Access Grid, the de facto Internet2 multimedia collaborative environment.

Related Work and Conclusion
There are some research works on bridging SIP and H.323 [8] [10].But these projects only deal with interworking between one kind of A/V endpoint and another one.Columbia University group [8]

Figure 1 :
Figure 1: Global-MMCS Architecture general session collaboration framework, which can support various kinds of collaboration tools.This framework includes two parts: one is XGSP (XML based General Session Protocol), which defines a general session protocol in XML.The other is WSDL-CI (WSDL Collaboration Interface), which gives an interface definition of any collaboration server.XGSP solves the issue of interconnecting the different collaboration tools for the same session.For example, we have AccessGrid, H.323 as well as SIP for videoconferencing.In order to make the servers and clients from different communities be able to communicate with each other, it is necessary to define only one session protocol which can be translated into AccessGrid, H.323, SIP messages and vice versa.WSDL-CI is used to describe the functionalities of the particular collaboration server.When we try to integrate the server into Global-MMCS, WSDL-CI provides the WSDL information to generate the interface component through which Global MMCS session server can control this collaboration server and add it into current active session.For example, the global session server can schedule a third-party H.323 MCU into the collaboration, if this MCU declares its interface in WSDL-CI, including the methods of session establishment, session membership and session collaboration control.There are different directories in Global-MMCS.The first is the directory of user account and media terminal.Unique user identifications help to authenticate valid users and bind the user to his media terminal.A user account may also include the information of user's media capability, for example, the audio terminal that the user wants to use.Also it is important to keep the directory of the active terminal, which the participant will use to access the media services.The second is the directory of different communities and collaboration servers.A community should be regarded as autonomous area that has its own collaboration control servers and media servers.

Figure 2
Figure 2 shows the architecture of Global-MMCS prototype system that we are developing.The XGSP Web Server, XGSP naming & directory server and XGSP session server implement the web-services framework of Global-MMCS.Through SOAP connection, the XGSP Web Server can invoke web-services provided by other communities, such as Admire and SIP.The XGSP Session Server translates

Figure 3 :
Figure 3: Comparison between the performance of NaradaBrokering and JMF defines the transformation of H.323 signaling procedure into SIP procedure and vice versa, which focus on VoIP service issue.And CMU group only implements a conference gateway [10] which connects multiple H.323 terminals and MBone clients.They don't have an integrated web-service framework and distributed event service middleware for heterogeneous collaborations.