An Investigation into Transport Protocols and Data Transport ...

9.3. Internet Transfers 230
9.3.1 Test Methodology
The variable loads and unpredictable performance of Internet traffic makes
obtaining consistent results across the Internet difficult. A long duration
single transfer test of each New-TCP algorithm to each host would yield
insufficient comparison between measurements as the network load may have
changed sufficiently such that it is a measurement of the variability of the
network, rather than that of the performance improvements of the New-TCP
algorithm.
However, running many short tests may not provide sufficient time for
the TCP flows to reach a steady state whereby the flow spends enough time
in congestion avoidance instead of slow start.
A simple solution would be to run the tests for a fixed number of bytes.
However, the variability of Internet performance may result in tests having
to run for a very long time due poor network goodput.
By imposing completely random start times and random sequences in
which the the various locations and New-TCP algorithms were run, unfair
comparison between algorithms due to the time based patterns of network
load is minimised. Therefore, many 5 minute TCP transfers were conducted
over the Internet from CERN in Switzerland to various locations in the
United States of America and Europe. The Internet link from CERN to
the Internet consisted of a 1Gb/sec connection. The hardware and software
specification of the test machine is defined in Table B.3.
All tests were run with the Linux 2.6.6 altAIMD-0.6 kernel using iperf
to conduct the TCP bulk transfers.
Table 9.1 shows the number of individual measurements that where taken
for each destination host and for each New-TCP algorithm. The tests were