**** Columbia Network Research Group Seminar ****

Title:    Does TCP Produce Self-Similar Traffic?
Speaker:  Prof. Don Towsley
          Univ. of Massachusetts, Amherst
When:     Wednesday, September 5, 2001 - 2 pm
Where:    Interschool Lab
          Seventh Floor, CEPSR building
          Columbia University
Host:     Prof. D. Rubenstein

ABSTRACT

The short answer is ``No.'' Contrary to recent claims made in the
literature that TCP congestion control creates self-similar traffic, we
show here that under realistic conditions, the traffic generated by a
long-lived TCP connection, while exhibiting pronounced correlations over
a finite range of time sales, is not consistent with long-range
dependence or (asymptotic) self-similarity.  Our conclusion is supported
by a careful statistical analysis of TCP trace data and by analytical
results derived from a versatile and well-established Markovian model of
TCP.  In particular, we analyze the same TCP traces used in previous
studies to ``prove'' that TCP creates self-similar traffic, but by
avoiding a number of pitfalls associated with inferring self-similar
characteristics, we arrive at a conclusion that directly contradicts the
claim of self-similarity but that fully conforms to the behavior
predicted by the analytic TCP model.  This work points out the
importance of careful trace analysis and detailed examination (and cross
validation) of alternative explanations when establishing or
characterizing the generality of any particular finding about Internet
traffic.

Joint work with A. Feldman, R. Figueiredo, B. Liu, V. Misra, W. Willinger