* [Ecn-sane] cwnd 4 in BBRv2?
@ 2019-03-28 17:09 Dave Taht
2019-03-29 0:03 ` [Ecn-sane] [bbr-dev] " Neal Cardwell
0 siblings, 1 reply; 2+ messages in thread
From: Dave Taht @ 2019-03-28 17:09 UTC (permalink / raw)
To: ECN-Sane, BBR Development, iccrg IRTF list
I just finished watching the sessions in ietf iccrg...
and although I have many questions about BBRv2, I am curious if the
cwnd in it is capped to a minimum of 4, not 2, still? BBRv1 is...
https://github.com/torvalds/linux/blob/master/net/ipv4/tcp_bbr.c#L385
--
Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Ecn-sane] [bbr-dev] cwnd 4 in BBRv2?
2019-03-28 17:09 [Ecn-sane] cwnd 4 in BBRv2? Dave Taht
@ 2019-03-29 0:03 ` Neal Cardwell
0 siblings, 0 replies; 2+ messages in thread
From: Neal Cardwell @ 2019-03-29 0:03 UTC (permalink / raw)
To: Dave Taht; +Cc: ECN-Sane, BBR Development, iccrg IRTF list
On Thu, Mar 28, 2019 at 6:10 PM Dave Taht <dave.taht@gmail.com> wrote:
>
> I just finished watching the sessions in ietf iccrg...
>
> and although I have many questions about BBRv2, I am curious if the
> cwnd in it is capped to a minimum of 4, not 2, still? BBRv1 is...
>
> https://github.com/torvalds/linux/blob/master/net/ipv4/tcp_bbr.c#L385
So far that part of the algorithm has not changed in BBRv2. So, except
for certain corner cases in loss recovery (e.g. cwnd=1 on RTO), the
min cwnd is generally 4.
But keep in mind that BBR generally tries to be pacing-limited, rather
than cwnd-limited. And below a cwnd of 4 delayed ACKs can inhibit
pipelining, causing stop-and-wait-type problems that significantly
hurt throughput.
best,
neal
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2019-03-29 0:03 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-03-28 17:09 [Ecn-sane] cwnd 4 in BBRv2? Dave Taht
2019-03-29 0:03 ` [Ecn-sane] [bbr-dev] " Neal Cardwell
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox