North American Network Operators Group
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Re: DNS problems to RoadRunner - tcp vs udp

  • From: Seth Mattinen
  • Date: Fri Jun 13 14:24:42 2008
Jon Kibler wrote: 
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Mark Price wrote:
<SNIP>

>From what I have read, public DNS servers should support both UDP and
TCP queries.  TCP queries are often used when a UDP query fails, or if
the answer is over a certain length.


UDP is used for queries.

TCP is used for zone transfers.

If my server responded to TCP queries from anyone other than a secondary
server, I would be VERY concerned.


I see long TXT records from some DNSBLs that won't fit in a UDP packet on a daily basis. Certainly nothing to be concerned about.

~Seth