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Principles for Collaboration Systems. Geoffrey Fox Community Grids Laboratory Indiana University Bloomington IN 47404 gcf@indiana.edu. Requirements or Issues to be Addressed I.
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Principles for Collaboration Systems Geoffrey Fox Community Grids Laboratory Indiana University Bloomington IN 47404 gcf@indiana.edu
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.
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
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
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
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
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