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SIGMETRICS 2001 / Performance 2001

On the Nonstationarity of Internet Traffic

Jin Cao <>
William S. Cleveland <>
Dong Lin <>
Don X. Sun <>

Statistics, Statistics, Networked Computing, Statistics Research, Bell Labs, Murray Hill

Traffic variables on an uncongested Internet wire exhibit a pervasive nonstationarity. As the rate of new TCP connections increases, arrival processes (packet and connection) tend locally toward Poisson, and time series variables (packet sizes, transferred file sizes, and connection round-trip times) tend locally toward independent. The cause of the nonstationarity is superposition: the intermingling of sequences of connections between different source-destination pairs, and the intermingling of sequences of packets from different connections. We show this empirically by extensive study of packet traces for nine links coming from four packet header databases. We show it theoretically by invoking the mathematical theory of point processes and time series. If the connection rate on a link gets sufficiently high, the variables can be quite close to Poisson and independent; if major congestion occurs on the wire before the rate gets sufficiently high, then the progression toward Poisson and independent can be arrested for some variables.

[Last updated Fri Mar 23 2001]

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