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CoopNet: Cooperative Networking

CoopNet: Cooperative Networking. Phil Chou, Venkat Padmanabhan, Helen Wang September 17, 2002. Motivation. “Flash crowd” can overwhelm server often due to news event of widespread interest… … but not always (e.g., Webcast of birthday party)

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CoopNet: Cooperative Networking

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  1. CoopNet: Cooperative Networking Phil Chou, Venkat Padmanabhan, Helen Wang September 17, 2002

  2. Motivation • “Flash crowd” can overwhelm server • often due to news event of widespread interest… • … but not always (e.g., Webcast of birthday party) • can affect relatively obscure sites (e.g., election.dos.state.fl.us, firestone.com, nbaa.org) • affects Web content as well as streaming content (live and on-demand) • infrastructure-based CDNs aren’t for everyone • Goal: solve the flash crowd problem!

  3. Cooperative Networking CoopNet Client-server Pure peer-to-peer • CoopNet complements client-server system • Client-server operation in normal times • P2P content distribution invoked on demand to alleviate server overload • Clients participate only while interested in the content • Server still plays a critical role

  4. Research Activities • Web flash crowd alleviation (with Kay Sripanidkulchai) • evaluation using Sep 11 traces from MSNBC • prototype implementation done • paper @ IPTPS ’02 • MDC-based streaming media distribution • evaluation using Sep 11 traces from MSNBC, Akamai, Digital Island • implementation in progress • paper @ NOSSDAV ’02 • patent process in progress • initial discussions with Digital Media Division

  5. Research Activities (contd.) • PeerMetric (with Karthik Lakshminarayanan) • characterize broadband network performance • P2P as well as client-server performance • working with Xbox Online (Mark VanAntwerp) • deployment on ~25 distributed nodes underway • eventual deployment on ~300 Xbox Live beta users • Future directions • CoopNet in a Wireless Mesh Network • good synergy: saves Internet bandwidth, improves robustness

  6. Robustness of Live Streaming • Peers are not dedicated servers  potential disruption due to: • node departures and failures • higher priority traffic • Traditional ALM is not sufficient

  7. Traditional Application-level Multicast

  8. CoopNet Approach to Robustness • Multiple description coding (MDC) • Multiple, diverse distribution trees

  9. Multiple Description Coding Layered coding MDC • Unlike layered coding, there isn’t an ordering of the descriptions • Every subset of descriptions must be decodable • Modest penalty relative to layered coding

  10. Multiple Description Coding • Simple MDC: • every Mth frame forms a description • More sophisticated MDC combines: • layered coding • Reed-Solomon coding • priority encoded transmission • optimized bit allocation

  11. Multiple Distribution Trees

  12. Tree Management • Goals: • short and wide trees • efficiency • diversity • quick join and leave processing • scalability • CoopNet approach: centralized protocol anchored at the server

  13. Centralized Tree Management • Basic protocol • nodes inform server of their arrival/departure • server tracks node capacity and tells new nodes where to join • each node monitors its packet loss rate and takes action when the loss rate becomes too high • simple, should scale to 1000+ joins/leaves per sec. • Optimizations • delay coordinates to estimate node proximity (à la GeoPing) • achieving efficiency and diversity • migrate “stable” nodes to a higher level in the tree

  14. Achieving Efficiency and Diversity NY SEA S Supernode SF

  15. MDC versus SDC Based on MSNBC traces from Sep 11

  16. CoopNet Transport Architecture Embedded Stream ZSF GOF Parse Packetize Optimize (M, p(m)) RD Curve Break Points M descriptions RS Encoder Server Internet Depacketize Embedded Stream(truncated) Reformat Decode Render GOF(quality depends on # descriptions received) m≤ M descriptions RS Decoder Client

  17. Summary • Robustness is the key challenge • MDC with multiple distribution trees improves robustness in peer-to-peer media streaming • Centralized tree management is efficient and can scales

  18. Current Activity • CoopNet media streaming system is being built • Evaluation: • adaptability • server scalability • media stream quality • overhead in MDC and control protocol • Dealing with client heterogeneity • combine MDC with layering

  19. Issues • Firewall and NAT traversal • Digital Right Management issues • ISP pricing policies • Enterprise scenarios

  20. Quality During Multiple Failures

  21. Quality During Single Failure

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