1. Principles for Collaboration Systems Geoffrey Fox Community Grids Laboratory Indiana University Bloomington IN 47404 gcf@indiana.edu

2. Requirements or Issues to be Addressed I Interoperability: Several standards – e.g. H323, T120, SIP, Access Grid – which are inconsistent with themselves and with modern Web standards Integration: Integrate all forms of collaboration – instant messenger, audio-video conferencing, application sharing Life-cycle costs: use commodity software components Extensibility: Interfaces defined for adding new capabilities Legacy: Support existing relevant infrastructure Network Quality of Service: communication links are dynamic and of variable quality and bandwidth.

3. Requirements or Issues to be Addressed II Performance: Allow maximum performance with given network with no unnecessary client or server overheads Fault Tolerance: Fault tolerant session control Security: Support multiple levels of security for clients, servers and communication traffic Scalability: Current systems are often limited by architecture or implementation (such as a single server) in number of simultaneous participants Pervasive Access: Need to support wide range of clients from hand-held devices to sophisticated desktop system. Ease of Use: Simple web portal interface; no special hardware Archiving: Universal mechanism for archiving collaborative session

4. Collaboration Architecture Use Grid and Web Service base architecture Define XML-based Collaboration Interface specification capturing semantics of existing standards Define open interfaces allowing both third party services to be developed and to allow competitive implementation of base infrastructure Use software overlay network to support needed dynamic routing and message-based architecture Use active measurements to find network performance and network or server/broker faults Use Web Service message based security Use publish/subscribe paradigm for all messaging to support multi-participant sessions and archiving Use distributed scalable fault-tolerant middleware including WS-RM (Web Service Reliable Messaging) or equivalent

5. Match of Requirements to Architecture I Interoperability: Can build services mapping betweens codecs and other architectures Integration: Overlay network supports all protocols and web service collaboration model supports all applications Life-cycle costs: Totally based on commodity web service architectures Extensibility: Framework for adding services defined in Web service standard fashion Legacy: Can build gateways of existing systems as Services and can interface with existing clients and Network Quality of Service: supplied by overlay network and dynamic performance/fault detection

6. Match of Requirements to Architecture II Performance: Commodity server overhead negligible compared to network transit time so can realize full performance allowed by communication channels Fault Tolerance: WS-RM and redundant distributed brokers and server fault detection Security: WS-Security gives standard compliant security with message-based security which is preferable to conventional connection based approach Scalability: Distributed Overlay Network Broker with dynamic servers has no scaling limit other than that of network Pervasive Access: Service model allows filters to drive any client with well defined interfaces Ease of Use: Web service infrastructure naturally supported by pervasive Web interfaces Archiving: Publish/subscribe architecture allows general archive to subscribe to all or part of a session

7. GlobalMMCS and Anabas Technology Prototypes using proposed architecture have been developed by Indiana University in an open source project and commercially by Anabas NaradaBrokering is open source publish/subscribe overlay network messaging system –Has performance monitoring driving dynamic routing –WS-RM reliability and WS-Security secure messages –Distributed brokers support full scalability XGSP is XML session protocol capturing H323 SIP and Access Grid Semantics – Gateways allow systems using these protocols to interoperate Web service middleware with sample services including PDA interface, codec conversion and media mixing Anabas supports text chat, shared display application while GlobalMMCS supports audio/video conferencing