SelfSimilar Wide Area Network Traffic

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 SIGCOMM94
• Extended version available by ftp

3
Introduction (Contd)

• 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