nanog mailing list archives
Re: ECN
From: Jon Lewis <jlewis () lewis org>
Date: Wed, 13 Nov 2019 12:57:10 -0500 (EST)
It does when the split flows land in different anycast origin POPs. Making a few assumptions from the traceroutes, the ECMP paths are sending some packets to Hamburg and some to Denmark. Each POP may be getting parts of what should be a single TCP stream, and I doubt they have anything to cope with that (another assumption).
On Wed, 13 Nov 2019, Matt Corallo wrote:
Not ideal, sure, but if it’s only for the SYN (as you seem to indicate), splitting the flow shouldn’t have material performance degradation?On Nov 13, 2019, at 11:51, Toke Høiland-Jørgensen <toke () toke dk> wrote: On 13 November 2019 17:20:18 CET, Matt Corallo <netadmin () 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.Even without anycast, an ECMP shouldn't hash on the ECN bits. Doing so will split the flow over multiple paths; avoiding that is the whole point of doing the flow-based hashing in the first place. Anycast "only" turns a potential degradation of TCP performance into a hard failure... :) -Toke
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Current thread:
- Re: TCP and anycast (was Re: ECN), (continued)
- 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)
- Message not available
- Re: ECN Toke Høiland-Jørgensen via NANOG (Nov 13)
- Re: ECN Matt Corallo (Nov 13)
- Re: ECN Anoop Ghanwani (Nov 13)
- Re: ECN Owen DeLong (Nov 13)
- Re: ECN Toke Høiland-Jørgensen via NANOG (Nov 14)
- Re: ECN Jon Lewis (Nov 13)