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The packet corruption is not seen to have a significant impact on the performance of file transfer for packet corruption < 8%. For packets > 8% being corrupted, the file transfer time is seen to increase. For packet corruption > 32%, the terminal itself became unresponsive and incapable of testing file transfer using PushPull.

Packet reordering

$ tc qdisc change dev eth0 root netem delay 100ms reorder 1% 50%

This argument implies that 1% of packets sent will be reordered and delayed by 100ms with the next packet having a probability of 0.5 of also being reordered. The packet delay as well as the next packet being reordered probability were kept constant throughout the evaluation.

Packet reordering was found to significantly increase the file transfer time for packet corruption > 16% with a very surprising decrease in the transfer time for 32%. This behaviour was noticed for several test runs using the same parameter set.

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Packet duplication

$ tc qdisc change dev eth0 root netem duplicate 1%

Although not a linear nor consistent increase in transfer time was found for packet duplication, an overall increase is marked. PushPull was found capable of dealing with great levels of packet duplication without stalling or terminating file transfer.

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Modified TCP window

A single file of 1024MB was downloaded using PushPull using different TCP window sizes. There is the option to enable/disable TCP window scaling in the configuration file /etc/sysctl.conf and to set the maximum transfer window under LINUX. The file is then reloaded to update the parameters using

$ sysctl -p

The parameters in /etc/sysctl.conf which were modified are (e.g.):

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Concurrent file transfer