nanog mailing list archives
Re: ECN
From: Anoop Ghanwani <anoop () alumni duke edu>
Date: Wed, 13 Nov 2019 09:19:15 -0800
Not to condone what cloudflare is doing, but... An ECN connection will have different bits on various packets for the duration of the connection -- pure ACKs (ACKs not piggybacking on data) will have the ECN bits as 00b, while all other packets will have either 01b, 10b (when no congestion was experienced) or 11b (when congestion was experienced). So using the ECN bits as part of the hash would affect performance throughout the life of the connection. On Wed, Nov 13, 2019 at 9:00 AM Matt Corallo <nanog () as397444 net> 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 sowill 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 ahard failure... :)-Toke
Current thread:
- Re: ECN, (continued)
- 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)
- 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)