nanog mailing list archives
Re: ECN
From: Lukas Tribus <lists () ltri eu>
Date: Wed, 13 Nov 2019 21:57:40 +0100
Hello, On Wed, Nov 13, 2019 at 8:35 PM Saku Ytti <saku () ytti fi> wrote:
On Wed, 13 Nov 2019 at 18:27, Matt Corallo <nanog () as397444 net> wrote:This sounds like a bug on Cloudflare’s end (cause trying to do anycast TCP is... out of spec to say the least), not a bug in ECN/ECMP.Not true. Hash result should indicate discreet flow, more importantly discreet flow should not result into two unique hash numbers. Using whole TOS byte breaks this promise and thus breaks ECMP. Platforms allow you to configure which bytes are part of hash calculation, whole TOS byte should not be used as discreet flow SHOULD have unique ECN bits during congestion. Toke has diagnosed the problem correctly, solution is to remove TOS from ECMP hash calculation.
In fact I believe everything beyond the 5-tuple is just a bad idea to base your hash on. Here are some examples (not quite as straight forward than the TOS/ECN case here): TTL: https://mailman.nanog.org/pipermail/nanog/2018-September/096871.html IPv6 flow label: https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse-hashing/ https://pc.nanog.org/static/published/meetings/NANOG71/1531/20171003_Jaeggli_Lightning_Talk_Ipv6_v1.pdf https://www.youtube.com/watch?v=b0CRjOpnT7w Lukas
Current thread:
- Re: ECN, (continued)
- Re: ECN Toke Høiland-Jørgensen via NANOG (Nov 13)
- Re: ECN Saku Ytti (Nov 13)
- Re: ECN William Herrin (Nov 13)
- Re: ECN Lukas Tribus (Nov 13)
- Re: ECN Saku Ytti (Nov 14)
- Re: ECN Tore Anderson (Nov 13)
- Re: ECN Warren Kumari (Nov 13)
- TCP and anycast (was Re: ECN) Anoop Ghanwani (Nov 13)
- Re: TCP and anycast (was Re: ECN) Bill Woodcock (Nov 14)
- Re: TCP and anycast (was Re: ECN) William Herrin (Nov 14)
- Re: TCP and anycast (was Re: ECN) Randy Bush (Nov 14)
- Re: TCP and anycast (was Re: ECN) Christopher Morrow (Nov 14)
- Re: TCP and anycast (was Re: ECN) Randy Bush (Nov 14)
- Re: ECN Toke Høiland-Jørgensen via NANOG (Nov 13)