Distributed Multimedia Systems James Maxlow March 24 th, 2003
Introduction § Most multimedia is inherently time-based – the arrival time and arrival order of data packets is important § The Internet guarantees neither when transmitting data § We don’t just want interactive multimedia over our networks… we want it to be reliable and high-quality § A distributed multimedia system can come to the rescue
History § 60 s-70 s: Distributed computing research with earliest networks § 80 s: Compact disc, personal computer explosion § 80 s-90 s: Distributed multimedia system research (video conferencing, et al) § 90 s: Current prevalent paradigm (quality of service management)
Goal § Simplicity in and of itself: We want and need high quality, reliable, interactive multimedia § The general Internet structure is not sufficient to accomplish this § A distributed multimedia system will add protocols and architectures on top of the Internet (or LAN) to guarantee quality levels, thereby satisfying our need
Definitions § Bandwidth: data rate through a component § Latency: time needed for a packet to travel end to end § Loss rate: acceptable drop-frame ratio § Quality of service management: negotiation and allocation of computing resources
Definitions § Flow specification: explicit representation of required resources § Traffic shaping: using buffers at source and destination to smooth data flow § Admission control: allowing or denying client requests based on available resources
Features and Structure 1: Sources provide flow spec to main QOS manager through local QOS managers 2: Main QOS ready to reserve resources Source QOS 3: Client send request to main QOS 4: Main QOS decides if client can be served based on available resources 5: If so, main QOS tells local QOS to allocate resources (if not, client is rejected) 6: Service begins 7: Main QOS and local QOS monitor resource usage / quality, adjust allocated resources if necessary 8: Return to step 4 if new client connects Main QOS 9: Service ends, resources are freed Controller Client Transmission Line (Internet)
How To Use § A distributed multimedia system is a combination of source hardware, QOS manager software, and a transmission line § Can be bought as a complete, dedicated, proprietary package – very expensive! § Can be built using existing hardware and Internet / LAN connection lines… all that is needed beyond that is QOS management software – can be purchased or developed
Applications § Video conferencing § Live news feeds § Video-on-demand § Remote-control of exploratory robots § Remote musical collaborations § Remote surgical operations
Significant Points § Distributed multimedia systems exist to guarantee quality of delivery levels § Resource reservation is the key § Additional clients do not degrade system – they can be refused if resources are scarce § Quality guarantees are of paramount importance, whether used for business, entertainment, scientific or health-related applications
Summary § Serving multimedia requires strict resource control to § § maintain quality Resources consist of bandwidth, latency, and loss rate, among others Source components declare the resources they need in flow specifications Quality of service managers negotiate and reserve resources to guarantee quality Source + flow spec + QOS manage + transmission lines = distributed multimedia system
References § § § Bashandy, Ahmed, Paul, R. , Baqai, S. , Sedigh, S. , Fahmi, H. , Ghafoor, A. “A Protocol Architecture for Guaranteed Quality of Service in Collaborated Multimedia Applications. ” Proceedings of the IEEE Symposium on Application -Specific Systems and Software Engineering & Technology. 1999. Coulouris, George, Dollimore, J. , Kindberg, T. Distributed Systems Concepts and Design, Third Edition. New York: Addison Wesley, 2001. Karr, David, Rodrigues, C. , Loyall, J. , Schantz, R. , Krishnamurthy, Y. , Pyarali, I. , Schmidt, D. “Application of the Qu. O Quality-of-Service Framework to a Distributed Video Application. ” Proceedings of the International Symposium on Distributed Objects and Applications. 2001. Loyall, Joseph, Schantz, R. , Zinky, J. , and Bakken, D. “Specifying and Measuring Quality of Service in Distributed Object Systems. ” Proceedings of the 1 st International Symposium on Object-Oriented Real-Time Distributed Computing. 1998. Stobart, Joel. “The use of Videoconferencing as a function of distributed organization: The differences of implementation depending on scale. ” Papers of the 2 nd Annual Conference on Multimedia Systems, Southampton Univ. , UK. 2002. Xu, Dongyan, Nahrstedt, K. , Wichadukal, D. “Qo. S and Contention-Aware Multi-Resource Reservation. ” Cluster Computing 4, pp. 95 -107. 2001. Websites: http: //www. cse. msu. edu/icdcs/ “ICDCS 2003” http: //www. idms 2001. org/ “i. DMS 2001” http: //mips 2003. idms-proms. org/ “MIPS 2003” http: //iwqos 03. cs. berkeley. edu/ “IWQo. S 2003” http: //www. computer. org/computer/timeline/ “Timeline of Computing History”
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