[dns-operations] Resolver preference: Long TCP sessions vs repeated handshakes?

Ray Bellis ray at isc.org
Fri Sep 23 13:16:00 UTC 2016

On 23/09/2016 13:47, Florian Weimer wrote:
> RFC 5966 section 5 suggests that concurrent TCP connections to resolvers
> should be avoided.

No, it says that they MUST be _minimized_.  That's altogether different.

That said, RFC 5966 has been replaced by 7766, which now says (§6.2.2):

   To mitigate the risk of unintentional server overload, DNS clients
   MUST take care to minimize the number of concurrent TCP connections
   made to any individual server.  It is RECOMMENDED that for any given
   client/server interaction there SHOULD be no more than one connection
   for regular queries, one for zone transfers, and one for each
   protocol that is being used on top of TCP (for example, if the
   resolver was using TLS).


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