From: "vinodh kumar" <[EMAIL PROTECTED]>

   UAC sends Invite with offer, UAS answers with inactive media and immediately
   sends re-invite with sendrecv media(for some strange reason).

   What should be the desired behavior at UAC side?.
   Should it terminate the call after sending ACK, or should it stay in media
   path hoping re-negotiation will take place.

I would strongly advise that the UAC, upon not establishing the media
streams that it considers necessary for the call, not terminate the
call immediately, but at least wait a "short while".

The reason for this is that SIP does seem to have situations where, in
order to implement particular call processing, requires transiently
establishing situations that might not be easy or useful to maintain
for any length of time.  Based on this principle, we assume that it is
possible that a call must be established with no usable media for a
short while.

(The case of the above rule that we have discovered in practice is the
situation where an agent X wishes to insert itself as a B2BUA into a
dialog between two agents A and B.  The only method that I know of to
implement this is for X to send an INVITE-with-Join to A, and then
send an INVITE-with-Replaces (with a different Call-Id) to B (which
ends the A-to-B dialog).  This requires a transient three-way call
(with demands to do media mixing) at agent A.  But in reality, agent A
need not be able to mix media, or at least, it needn't be able to do
it well, as the three-way call situation has very short duration.)

Dale
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