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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
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!


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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


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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


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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


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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


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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


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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



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Tree Management

  • Goals:

    • short and wide trees

    • efficiency

    • diversity

    • quick join and leave processing

    • scalability

  • CoopNet approach: centralized protocol anchored at the server


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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


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Achieving Efficiency and Diversity

NY

SEA

S

Supernode

SF


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MDC versus SDC

Based on MSNBC traces from Sep 11


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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


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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


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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


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Issues

  • Firewall and NAT traversal

  • Digital Right Management issues

  • ISP pricing policies

  • Enterprise scenarios




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