Messages in this thread | | | From | Neal Cardwell <> | Date | Wed, 3 Apr 2019 11:39:34 -0400 | 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 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>
Thank you for this patch, Olivier and Bob.
thanks, neal
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