[dns-operations] TCP anycast was Re: DNS query logging
Francis Dupont
Francis.Dupont at fdupont.fr
Fri Mar 18 23:33:58 UTC 2011
In your previous mail you wrote:
Perhaps. But then again maybe not. TCP is a relation between two
end points, in between it is IP. If the path changes out below a TCP
session and the routing converges before a timeout happens, TCP
wouldn't care. However, it's been decades before I had deep enough
knowledge to give any specifics.
With UDP, any sneeze may lose the packet. But even if it whirlpools
a bit before getting home, so long as it's in the time window, it's
okay.
=> in fact you missed another case: I saw only once anycast leading
to a broken service:
- a load-balancer was in front of a pool of (two) servers
- the load-balancer became a bit bad and duplicated packets,
i.e., sent incoming packets to both servers in place of selecting
on at the first packet of a flow and keeping it
- TCP queries failed in a strange way getting both answers and TCP
resets
- the load-balancer was rebooted
and the service has been worked pretty well since many years...
Regards
Francis.Dupont at fdupont.fr
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