[dns-operations] TCP anycast was Re: DNS query logging

Dobbins, Roland rdobbins at arbor.net
Thu Mar 17 14:06:04 UTC 2011

On Mar 17, 2011, at 8:32 PM, Edward Lewis wrote:

> Just want to know how TCP query works in anycast dns server. Will be there any drawback using TCP in anycast

As you already surmise, same as with UDP.

There's this myth that anycast isn't suitable for TCP-based applications because of the stateful nature of TCP connections.  But the truth of the matter is that if routing is unstable enough to seriously disrupt sessions to any given anycast node, there are much larger fish to fry on the network(s) in question.

> We haven't experienced any negative issues relating anycast over TCP.  As in, we have it set up, don't do anything special about it, and it isn't mentioned in system status (ticket) meetings.

Your experience is representative of other real-world TCP-based anycast deployments, It Just Works.  Nothing broken, so nothing to fix - don't listen to the naysayers, they don't have the production experience you do.


Roland Dobbins <rdobbins at arbor.net> // <http://www.arbornetworks.com>

		The basis of optimism is sheer terror.

			  -- Oscar Wilde

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