Re: ECN

[Matt Corallo <nanog () as397444 net>]

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