Ralf Weber wrote:
>> It should be noted that unicast TCP is unstable if unicast routing
>> is unstable.
>
> Yes, but TCP usually adapts to the problem while anycast can't, as it
> may reach another target.
That unicast TCP fails in unusual cases means we, anyway, need
retry mechanisms, which helps anycast TCP.
> As someone who has deployed anycast DNS
> within a carrier network there are some things to consider , e.g don't
> put anycast routes in fast converging routing protocols and be careful
> with multi links for similar destinations. But if you follow the rules
> it can be deployed and also works with tcp transport for DNS....at
> least for me.
Could you elaborate on how fast converging routing protocols can
be a problem?
Anycast TCP fails only when route changes upon a link failure or
recovery. So, anycast TCP should fail regardless of how quickly
or slowly the route changes, shouldn't it?
I can understand that, with multi links, packet-wise load balancers
disturbing packet ordering within TCP streams are, of course, harmful
to anycast TCP.
Masataka Ohta
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