Bob Harold wrote:

...

Unfortunately, the resolver needs to make decisions based on the
original transport, for example if the transport is TCP, it can send any
size response.  But if UDP, it needs to fit in a smaller size, and it
often sends less info in the response.  Likewise, session signalling,
anti-spoofing decisions, etc depend on the transport.

except that i don't find it unfortunately but simply factual, i agree.


That brings up another question.  Would it also need to know the MTU of
the original connection, or any other info?  (Assuming EDNS is not
used)  In that case, a different media type is not enough, and we need
to change the format to add some 'header" info.

not in my opinion. if the far end has a larger MTU outbound than the near end had inbound, then truncation damage will occur -- and the original initiator will retry with TCP. we just need to be transparent so that the original initiator can drive its own transport selections.

--
P Vixie

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