Re: Very poor TCP/SACK performance

Rik van Riel (H.H.vanRiel@phys.uu.nl)
Thu, 10 Sep 1998 20:23:06 +0200 (CEST)

On 9 Sep 1998, Mark Gray wrote:
> Jeff DeFouw <mrj@i2k.com> writes:
> > On Tue, 8 Sep 1998, David S. Miller wrote:
> >
> > > One thing you can try to alleviate this situation is to up the default
> > > window sizes a bit using the knobs in:
> > They're already set to 65535, but I don't understand how increasing a
> I think ppp over modem is a special case where a larger window is very
> often bad depending on what hardware is in between --- the reason
> (IMO) is that most of window is going to get queued up in your ISP at
> the choke point --- their terminal controller/modem hardware --- and a
> large window might be big enough to tickle problems on their end.

I tried reducing the window size, and it gives me some 10%
more bandwidth and a more responsive connection over my
28.8 PPP link to university.

Maybe Linux should reduce the window size if it detects a
lot of out-of-order packets coming in. If the TCP code has
a way of knowing the properties of the connection networking
is done over, it might be able to set these flags itself.

ie: if(small_buffer_other_side && lots_out_of_order()) size--;

Networking guys, what about this?

Rik.
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