[Iccrg] improvement of tcp slow start

[Michael Welzl]

On Fri, 2007-03-16 at 14:45 +1100, Lachlan Andrew wrote:
> Greetings Stefan,
> 
> The main problem with increasing the rate of increase of slow start is
> that it creates larger overshoot when the correct rate is reached.  If
> we triple the rate each RTT instead of doubling it (or multiplying by
> 1.5 -- see the recent discussion on the end2end-interest list), then
> we are transmitting at three times too fast when we finish.
> 
> What would be more useful would be something which can detect when
> slow-start is nearing its end -- like measuring queueing delay or some
> property of the RTT-level burstiness -- so that we can start
> aggressively but back off when we're nearing the end.

That sounds like a really good idea to me!


> There are also fairness issues with having some sources using
> "improved" slow start and some using the existing algorithm, although
> I think they're often overstated.

I agree (i.e. I also think they're overstated). In a world where
non-TCP-friendly highspeed TCP variants are already used, who
cares about one flow starting up a bit faster than the other,
especially when it would make a major difference in performance
for most real (i.e. short) flows?

Cheers,
Michael