I stand corrected. RFC 1035 section 4.2:

"The DNS assumes that messages will be transmitted as datagrams or in a
byte stream carried by a virtual circuit.  While virtual circuits can be
used for any DNS activity, datagrams are preferred for queries due to
their lower overhead and better performance.  Zone refresh activities
must use virtual circuits because of the need for reliable transfer."

"The Internet supports name server access using TCP [RFC-793] on server
port 53 (decimal) as well as datagram access using UDP [RFC-768] on UDP
port 53 (decimal)."

-matt

On Thu, 25 Sep 2003, Jan L. Peterson wrote:

> > dns uses udp not tcp...  you opened the tcp port 53... you need to
> > upen udp pot 53 instead.
>
> Actually, DNS uses both UDP and TCP.  It will normally use UDP, but for
> larger requests (that will not fit in a single UDP packet) it must use
> TCP.  Open both TCP and UDP.
>
>       -jan-
> --
> Jan L. Peterson
> Semi-Unemployed "Computer Facilitator"
> http://www.peterson.ath.cx/~jlp/resume.html
>
>
>
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