[e2e] Performance factors of TCP Equation Model

Yunhong Gu1 ygu1 at cs.uic.edu
Fri Sep 10 13:22:03 PDT 2004

> If the TCP-Friendly Protocol flows in both scenarios employ the same model
> (Padhye et
> al.), with different RTT how they will eventually achieve the ideal
> bandwidth share, i.e.
> 100Kbps. I can’t see loss rate can do that.

Hi, Chua,

Why do you think loss rate cannot do that?

Although the RTT values are different in the two scenarios, the loss
rate can also be different, and this formula could still reach same

1.3 * MTU / (RTT * sqrt(LossRate))

Of course if the RTT value is too large, TCP flows may not reach 100%
utilization of the bandwidth. In this case, the formula can only help to
reach fairness on the same link. For example, in senario 1, all flows may
end at 90kbps, whereas in scenario 2, all flows may end at 95kbps.

I think your assumption that all flows will reach 100kbps is where the
confliction comes from.


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