1 Self-Similar Ethernet LAN Traffic Carey Williamson University of Calgary

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

3 Introduction (Cont’d) u Extended version of the paper appeared in the IEEE/ACM Transactions on Networking, Vol. 2, No. 1, February 1994 u One of the landmark papers of the ‘90’s u Highly regarded, influential, one of the most cited papers in the last 3 years

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

5 Self-Similarity: A Hot Topic u Several papers since then have identified network traffic self-similarity in OTHER types of traffic (video, Internet, Web) u Several models for self-similar traffic have been proposed in the literature u Several studies of the performance implications of self-similar traffic and long-range dependence

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

7 Data Analysis u Detailed statistical analysis: –aggregation, autocorrelation, R/S analysis, variance-time plot, periodograms, Whittle’s estimator, maximum likelihood... u Very rigourous: confidence intervals, sophisticated statistical tests, sound methodology,... u A wonderful paper to read (over and over)

8 Main Results u Aggregate Ethernet LAN traffic is self-similar u Burstiness across many time scales u Hurst parameter 0.7 < H < 0.9 u H is larger when network utilization is higher (e.g., 0.9 when U = 15%) u Self-similarity present on all LAN’s tested

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