Paul Heinlein wrote:
On Thu, 23 Aug 2007, Feizhou wrote:
You only need the tcp rule if you plan on serving up zone
transfers, not if plan on only requesting them.
Well, very rare but answers that are over 512 bytes will have to be
sent over tcp since the rfc 1035 mandates maximum 512 bytes for the
udp payload. So tcp is not just for zone transfers only.
Note that by default Win 2003 uses a packet size of 1280 per Paul
Vixie's suggestion in RFC 2671 section 4.5.1. I don't know if any other
OS implementations do the same.
In any event, I've found it helpful to allow up to 1280 bytes of DNS UDP
traffic. Setting the limit at 512 triggers a noticable number of
retries, at least in our environment.
Sigh. I can see some caching servers with big scissors to apply to udp
packets...if they at all issue queries that get such large replies...
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