[e2e] Open the floodgate

[Saad Biaz]

On Fri, 23 Apr 2004, Fu Cheng Peng, Franklin wrote:

> One possible solution  to solve the loss type distinghishing between
> congestion loss and random loss, seeing TCP Veno at JSAC Feb.. 2003, or
> at http://www.ntu.edu.sg/home/ascpfu/veno.pdf

TCP-Veno is based on the TCP-Vegas congestion avoidance scheme. We
analyzed this scheme to test whether it could be used as a loss
discriminator: it is a poor discriminator. There are some rare cases when
TCP-Vegas is a good discriminator...(Google on "biaz vaidya
distinguishing").
Look at Hengartner (Infocom 2000) on the impact on the "new" congestion
avoidance scheme on TCP-Vegas performance.

A lot of work is done along the lines of Veno: researchers use some
heuristics to distinguish congestion losses from other types of losses and
evaluate their scheme by looking at the throughput improvement. Very
often, the accuracy of the differentiation is not measured. This means
that many congestion losses are misclassified and the TCP-XX does not
respond to these losses. Such a behavior may be risky for the network.

If there is a scheme to distinguish congestion losses from other losses,
FIRST MEASURE ITS ACCURACY and report it. If you find that you accurately
diagnose 90 to 95% of congestion losses and
more than 50% of other losses, then proceed to measure the
throughput improvement.

Matta has shown that even with poor loss discriminators, you would get
better throughput.


Saad

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Saad Biaz, Ph.D., Assistant Prof.     Voice: (334) 844 6307
114 Dunstan Hall Auburn University    Fax  : (334) 844 6329
Auburn, AL 36849-5347, USA            http://www.eng.auburn.edu/~sbiaz
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