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Simulated Workload

Most of this information required to generate the simulation input files (described in the next section) was gathered from HTTP logfiles collected from the New Zealand Internet exchange (NZIX). The trace files used were collected from 3:00pm to 3:10pm in July 1997. There were, on average, 421 requests1 per interval. To generate higher loads than that experienced when the trace files were collected, traces for the same time on successive days in July were integrated into a single trace. When higher still loads were required more than one copy of each trace was integrated into the logfile. Each copy was offset in time to minimise the effect of the artificial self correlation of the trace generated in this way. The TCP MSS and server buffer sizes are not recorded in the HTTP traces we used. To discover these parameters a connection was established to each host while the network traffic was monitored using tcpdump. From the tcpdump output the MSS and window size was discovered for most hosts. Some hosts did not advertise their MSS. In this case the most common MSS (1480) was used.

Footnotes

... requests1
The actual trace incudes more requests. This number is the number of successful international requests that were not satisfied by the cache hierarchy

next up previous
Next: Simulator Design Up: The effect of multiplexing Previous: Simulated Network
A.McGregor, M.Pearson, J.Cleary
November 1998