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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 l.jpg

CoopNet: Cooperative Networking

Phil Chou, Venkat Padmanabhan, Helen Wang

September 17, 2002

Motivation l.jpg

  • “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.,,,

    • 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!

Cooperative networking l.jpg
Cooperative Networking



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

Research activities l.jpg
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

Research activities contd l.jpg
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

Robustness of live streaming l.jpg
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

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CoopNet Approach to Robustness

  • Multiple description coding (MDC)

  • Multiple, diverse distribution trees

Mu l tiple description coding l.jpg
Multiple Description Coding

Layered coding


  • Unlike layered coding, there isn’t an ordering of the descriptions

  • Every subset of descriptions must be decodable

  • Modest penalty relative to layered coding

Multiple description coding l.jpg
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

Tree management l.jpg
Tree Management

  • Goals:

    • short and wide trees

    • efficiency

    • diversity

    • quick join and leave processing

    • scalability

  • CoopNet approach: centralized protocol anchored at the server

Centralized tree management l.jpg
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

Achieving efficiency and diversity l.jpg
Achieving Efficiency and Diversity






Mdc versus sdc l.jpg
MDC versus SDC

Based on MSNBC traces from Sep 11

Coopnet transport architecture l.jpg
CoopNet Transport Architecture

Embedded Stream






(M, p(m))



Break Points

M descriptions

RS Encoder




Embedded Stream(truncated)




GOF(quality depends on # descriptions received)

m≤ M descriptions

RS Decoder


Summary l.jpg

  • 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

Current activity l.jpg
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

Issues l.jpg

  • Firewall and NAT traversal

  • Digital Right Management issues

  • ISP pricing policies

  • Enterprise scenarios