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Self-Similar Wide Area Network Traffic

Self-Similar Wide Area Network Traffic

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Self-Similar Wide Area Network Traffic

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  1. Self-Similar Wide Area Network Traffic Carey Williamson University of Calgary

  2. Introduction • A recent paper has established the presence of network traffic self-similarity in wide area Internet traffic as well • “Wide Area Traffic: The Failure of Poisson Modeling” • Authors: Vern Paxson and Sally Floyd • ACM SIGCOMM’94 • Extended version available by ftp

  3. Introduction (Cont’d) • Original intent: show that self-similarity is not present in WAN traffic • Failed! • Self-similarity IS present in WAN traffic • Identified where it appears and where it does not • Identifies limitations of Poisson models

  4. Main Contributions • Identified presence of self-similarity property in Internet traffic • Defined methodology for testing for the presence of self-similarity, and for testing the goodness of Poisson models • Identified importance of “heavy tails” • Proposed explanations/models for SS • Proposed complete model for telnet

  5. Measurement Study • Detailed measurement study of very lengthy Internet packet traces, with high resolution timer, and lots of storage space • Traces range from 1 hour to 30 days in duration • Millions of TCP packets and connections • Several different sites

  6. Data Analysis • Detailed statistical analysis: • connection interarrivals, per application analysis, packet level, connection level, tests for Poisson-ness, models, evaluation, ... • Very rigourous: confidence intervals, sophisticated statistical tests, sound methodology, ... • A wonderful paper to read

  7. Main Results • Connection arrivals for telnet appear to be Poisson, but... • Packet arrivals are definitely not Poisson • Connection arrivals for ftp and other applications do not appear to be Poisson • Traffic exhibits long range dependence and other aspects of self-similarity

  8. Conclusions • Self-similarity is present in aggregate WAN Internet traffic • Poisson models (or Markovian models of any sort) do not capture reality at all (except possibly for telnet connection arrivals) • Important to consider self-similar traffic