DNS problems to RoadRunner - tcp vs udp

Sun Jun 15 08:12:48 UTC 2008

* Jon Kibler:

>>>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.

I've seen such claims countless times.  8-( However, you can perform
zone file transfers over UFP in some cases (using IXFR), and TCP
fallback may happen even if you never respond with packets with the TC
bit set.