> On 24 Jun, 2019, at 9:57 pm, David P. Reed <dpreed@deepplum.com> wrote:
>
> TCP doesn't have a "natural sawtooth" - that is the response of TCP to a particular "queueing discipline" in a particular kind of a router - it would respond differently (and does!) if the router were to drop packets randomly on a Poisson basis, for example. No sawtooth at all.
I challenge you to show me a Reno or CUBIC based connection's cwnd evolution that *doesn't* resemble a sawtooth, regardless of the congestion signalling employed. And I will show you that it either has severe underutilisation of the link, or is using SCE signals. The sawtooth is characteristic of the AIMD congestion control algorithm.
Jonathan,
even if it is news to nobody,
AIMD does not necessarily converge to a limit cycle (e.g. a sawtooth). It depends on some regularity conditions of the AIMD law and congestion feedback too.
For instance, AIMD delay based congestion control or AIMD with certain ECN laws may display no limit cycles. Still under certain conditions.
Just to recall that the problem is a little more complex than that in general.
- Jonathan Morton
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