[Ecn-sane] cwnd/2 - 1

[Ecn-sane] cwnd/2 - 1

[Dave Taht]

One of the things that went by in recent kernel changes was that
linux tcp at a cwnd 2 on a CE goes into quickack mode, so that we
get back one ack per packet (I think, from reading the commit) instead of
every other one.

halving cwnd and then taking off 1 more gives a response that drops the
mass closer along the lines of what a drop may do in response to loss
and re-ordering. A cwnd 1 in quickack mode would halve the number of
packets outstanding in my 100 flows test. I think.

another thing to note is that retransmits, are, by the standard, and
in linux, not protected by ECT, and when you get near to 100% mark
rate as i do in this artificial test, get dropped a lot.



-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619

Re: [Ecn-sane] cwnd/2 - 1

[Pete Heist]

> On Sep 7, 2018, at 9:18 AM, Dave Taht <dave.taht@gmail.com> wrote:
> 
> One of the things that went by in recent kernel changes was that
> linux tcp at a cwnd 2 on a CE goes into quickack mode, so that we
> get back one ack per packet (I think, from reading the commit) instead of
> every other one.

For my understanding, when does tcp return to delayed ack mode, once cwnd increases again?