[lug] TCP port 53?

[John Hernandez]

>>>I know DNS uses UDP, but does it use TCP as well?
>>
>>Yes.  It will switch to TCP for any requests that are too large to fit 
>>in a UDP packet.
>>
> 
> as i understand it it uses udp for queries and tcp for zone xfers.  it
> has nothing to do with size.

Jeffrey is correct.  The query is first tried using UDP.  Then, if the 
response is longer than the allocated buffer, the resolver will retry 
using TCP.  Some implementations may not behave this way, however.

As Dan stated, zone transfers are also accomplished using TCP/53.

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