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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

CoopNet: Cooperative Networking

Phil Chou, Venkat Padmanabhan, Helen Wang

September 17, 2002

  • “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
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
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
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
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
coopnet approach to robustness
CoopNet Approach to Robustness
  • Multiple description coding (MDC)
  • Multiple, diverse distribution trees
mu l tiple description coding
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
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
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
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
mdc versus sdc
MDC versus SDC

Based on MSNBC traces from Sep 11

coopnet transport architecture
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


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