tcp versus udp
Barry Margolin
barmar at alum.mit.edu
Thu May 7 05:12:26 UTC 2009
In article <gtrqte$2ins$1 at sf1.isc.org>,
Sam Wilson <Sam.Wilson at ed.ac.uk> wrote:
> In article <gtrbsa$296l$1 at sf1.isc.org>, Mark Elkins <mje at posix.co.za>
> wrote:
>
> > One place that TCP may make sense - if you are involved in a registry
> > system and the process involves actually checking the information that
> > you are given, including nameservers (do they exist, do they serve that
> > zone - correctly?) - it may make a lot of sense to do TCP Digs for the
> > information (though that should probably be after a failed UDP dig - as
> > a number of people do insist on disallowing Port 53 TCP).
>
> If the registry is testing for compliant servers then a failed TCP query
> should flag the server as non-working, as would a failed UDP query.
DNS servers MUST support UDP, and only SHOULD support TCP. So a failed
TCP query should not flag the server as non-working.
--
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***
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