Why server output from disallowed interface?

[Barry Margolin]

In article <c1dpma$15k8$1 at sf1.isc.org>, phn at icke-reklam.ipsec.nu wrote:

> > My understanding is that TCP is only used when a zone transfer is too big to
> > fit in a a UDP packet.  Thus I should only *transmit* on TCP to transfer
> > zone info to other machines on my network, right?
> wrong. UDP and TCP is used for queries/responses, for zone-transfers
> TCP is always used.

I think he didn't get the precise wording right, but he was correct when 
he said that TCP is only supposed to be used when the response is too 
big to fit in a UDP packet.

However, Microsoft Exchange is a known violator of this requirement.  It 
queries for MX records using TCP.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA