Messages in this thread | | | From | Yuchung Cheng <> | Date | Wed, 3 Apr 2019 08:51:35 -0700 | Subject | Re: [PATCH net-next] tcp: Accept ECT on SYN in the presence of RFC8311 |
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On Wed, Apr 3, 2019 at 8:39 AM Neal Cardwell <ncardwell@google.com> wrote: > > On Wed, Apr 3, 2019 at 9:50 AM Tilmans, Olivier (Nokia - BE/Antwerp) > <olivier.tilmans@nokia-bell-labs.com> wrote: > > > > Linux currently disable ECN for incoming connections when the SYN > > requests ECN and the IP header has ECT(0)/ECT(1) set, as some > > networks were reportedly mangling the ToS byte, hence could later > > trigger false congestion notifications. > > > > RFC8311 §4.3 relaxes RFC3168's requirements such that ECT can be set > > one TCP control packets (including SYNs). The main benefit of this > > is the decreased probability of losing a SYN in a congested > > ECN-capable network (i.e., it avoids the initial 1s timeout). > > Additionally, this allows the development of newer TCP extensions, > > such as AccECN. > > > > This patch relaxes the previous check, by enabling ECN on incoming > > connections using SYN+ECT if at least one bit of the reserved flags > > of the TCP header is set. Such bit would indicate that the sender of > > the SYN is using a newer TCP feature than what the host implements, > > such as AccECN, and is thus implementing RFC8311. This enables > > end-hosts not supporting such extensions to still negociate ECN, and > > to have some of the benefits of using ECN on control packets. > > > > Signed-off-by: Olivier Tilmans <olivier.tilmans@nokia-bell-labs.com> > > Suggested-by: Bob Briscoe <research@bobbriscoe.net> > > Cc: Koen De Schepper <koen.de_schepper@nokia-bell-labs.com> > > Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Yuchung Cheng <ycheng@google.com>
> > Thank you for this patch, Olivier and Bob. > > thanks, > neal
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