Self-Similar Ethernet LAN Traffic

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Self-Similar Ethernet LAN Traffic

• Carey Williamson

University of Calgary
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Introduction

• The original paper on network traffic
  self-similarity appeared at the 1993 ACM SIGCOMM
  Conference on Communications Architectures and
  Protocols
• Authors Will Leland, Murad Taqqu, Walter
  Willinger, and Daniel Wilson (Leland et al. 1993)

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Introduction (Contd)

• Extended version of the paper appeared in the
  IEEE/ACM Transactions on Networking, Vol. 2, No.
  1, February 1994
• One of the landmark papers of the 90s
• Highly regarded, influential, one of the most
  cited papers in the last 3 years

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Main Contributions

• Identified presence of self-similarity property
  in aggregate Ethernet traffic
• Defined methodology for testing for the presence
  of self-similarity
• variance-time plot
• R/S statistic
• periodogram (power spectrum)
• Proposed explanations/models for SS

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Self-Similarity A Hot Topic

• Several papers since then have identified network
  traffic self-similarity in OTHER types of traffic
  (video, Internet, Web)
• Several models for self-similar traffic have been
  proposed in the literature
• Several studies of the performance implications
  of self-similar traffic and long-range dependence

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Measurement Study

• Detailed measurement study of very lengthy
  Ethernet packet traces, with high resolution
  timer, and lots of storage space
• One of the traces presented in their paper is a
  27.5 hour trace
• Over 20 million packets

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Data Analysis

• Detailed statistical analysis
• aggregation, autocorrelation, R/S analysis,
  variance-time plot, periodograms, Whittles
  estimator, maximum likelihood ...
• Very rigourous confidence intervals,
  sophisticated statistical tests, sound
  methodology, ...
• A wonderful paper to read (over and over)

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Main Results

• Aggregate Ethernet LAN traffic is
  self-similar
• Burstiness across many time scales
• Hurst parameter 0.7 lt H lt 0.9
• H is larger when network utilization is
  higher (e.g., 0.9 when U 15)
• Self-similarity present on all LANs tested

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Conclusions

• Self-similarity is present in aggregate Ethernet
  LAN traffic
• Traffic does not aggregate well at all
• Law of large numbers may not hold!
• Poisson models (or Markovian models of any sort)
  do not capture reality at all
• Important to consider self-similar traffic