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CoolStreaming/DONet: A Data-driven Overlay Network for Peer-to-Peer Live Media Streaming Authors: Xinyan Zhang., Jiangchuan Liu, Bo Li, and Tak-Shing Peter Yum. Presenter: Elaine 1 Outline Introduction Related Work Design and Optimization of Donet Planet-Based Performance Evaluation CoolStreaming Conclusion and Future works 2 Multimedia applications IP multicast is the best way Live media streaming from a source to a large population of users. NetTV, news broadcast The lack of incentives to install multicast routers Political and practical issues Application-level solution: Overlay network Built on the unicast tunnels across cooperative participating users. 3 Features of overlay network with streaming application. Easily crash/leave Streaming application Many overlay construction algorithms advocate a tree structure for data delivering. High bandwidth Continuity highly vulnerable. Restriction of the flow directions Proposed data-centric overlay network No predetermined roles Self-organization Data availability guides the flow directions. 4 Outline Introduction Related Work Design and Optimization of Donet Planet-Based Performance Evaluation CoolStreaming Conclusion and Future works 5 A brief overview of the existing overlay streaming protocols in the pure p2p paradigm Tree-based protocol An internal node with high load leaving or crashing often causes underflow in a large population of descendants. Unbalanced load Repairing mechanisms are complex. 6 Gossip-based protocol A node sends a newly generated message to a set of randomly selected nodes, iteratively. Cause redundancy especially for media streaming application. Partially used for membership management and data delivery in Donet 7 Outline Introduction Related Work Design and Optimization of Donet Planet-Based Performance Evaluation CoolStreaming Conclusion and Future works 8 Three key modules Membership manager Partnership manager Scheduler 9 Interaction of modules A. Node join and Membership Management Each Donet node has a unique id and Mcache. How to create and update the mcache. Each node periodically generates a membership message to announce its existence SCAM(Gossip) to distribute the mcache messages.. Message format: <seq num, id,num partner, time to live> Entry Message format: <seq num, id,num partner, time to live,last_update_time> Node join algorithm 10 B. Buffer Map Representation and Exchange A video stream is divided into segments of uniform length Buffer Map: represent the availability of the segments Continuously exchange BM with partners, and schedules which segment is to be fetched from which partner accordingly. 11 12 D. Failure Recovery and Partnership Refinement Failure Recovery Graceful departure Node failure Partnership Refinement Periodically establish new partnerships with nodes randomly selected from its mCache. Node i use function max{¯si,j , ¯sj,i} to score its partners ¯si,j: the average number of segments that node i retrieved from node j per unit time. ¯sj,i: the average number of segments that node j retrieved from node j per unit time. 13 Outline Introduction Related Work Design and Optimization of Donet Planet-Based Performance Evaluation CoolStreaming Conclusion and Future works 14 A. Design of the Experiment System Almost all active nodes over PlanetLab,200~300 Experiment May to June, 2004 Each active PlanetLab node runs a copy of the prototyped program,acting a s a DONet node. Origin node: Located in the United States Monitoring node: In Hong Kong 15 B. Performance under Stable Environment All nodes persist in the lifetime of the streaming(120min) Control overhead(left) Scalability(left) Playback continuity(right). 16 C. Performance under Dynamic Environment Dynamic node joining , leaving, and failure. Following the ON/OFF model. 17 D. Comparison with the Tree-based Overlay Metrics: End-to-End delay / Continuity The number of partners is set to 4 in Donet. The degree of each tree node is limited to 3, except root(4). Different capacity and bandwidth cause some children move to lower levels. Fig 11/fig12/fig 13 18 A full and balanced 3-ary tree of 231 nodes has a height of 5 only. 19 20 Summary and Caveats Performance of Donet is acceptable Overhead is low(1% of the video traffic) Scalability Compared to tree-based overly Continuity is much better under highly dynamic environment. End-to-end delay is comparable. Caveats Scalability Representability 21 Outline Introduction Related Work Design and Optimization of Donet Planet-Based Performance Evaluation CoolStreaming Conclusion and Future works 22 A public Internet based DONet package, called CoolStreaming. Released the first version (v.0.9) on May 30, 2004. CoolStreaming v.0.9 23 Two interesting facts: The current Internet has enough available bandwidth to support TV-quality streaming(>=450 Kbps) The larger the data-driven overlay is, the better the streaming quality it delivers. 24 Conclusion Proposed DONet Simple overlay structure (according to the data availability) Scalable membership and partnership management algorithm Good playback quality under formidable network condition Compared to tree-based overlay,it achieves much more continuous streaming with comparable delay. Released CoolStreaming v.0.9 25