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

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

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

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

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

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

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

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