1. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20111 Self-Similarity in WAN Traffic A subsequent paper established the presence of network traffic self-similarity in wide area Internet traffic as well “Wide Area Traffic: The Failure of Poisson Modeling”, by Vern Paxson and Sally Floyd, ACM SIGCOMM 1994 Their original intent was to show that self-similarity is not present in WAN traffic, but they failed! Self-similarity is present in WAN traffic Identified where it appears and where it does not Identifies limitations of Poisson models

2. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20112 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

3. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20113 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

4. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20114 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

5. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20115 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

6. Copyright © 2005 Department of Computer Science CPSC 641 Winter 20116 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