Subject: [Sip] Early media proposal.

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Mon, 6 Aug 2001 15:47:40 -0700

Hi Jonathan,

I really like the 18x/PRACK offer/answer model for early media. However, in
order in order to avoid the high (IMO) conceptual and programmtic complexity
of the potential overlapping invites (which I'm sure will result in only one
thing - a lot of people not implementing it fully) I have an alterative
suggestion.

Instead of having overlapping invites (when the caller wants to initiate a
media change), simply devise a mechanism to trigger the callee to resend a
18x early media offer. In this manner all the logic is re-used, all the call
setup is kept (seamlessly) in the same SIP transaction and it is a lot
conceptually simpler (which in my book counts for a lot). 

The simplest mechanism is to merely come up with a new method that the
caller sends - which has no state in itself - that simply causes the callee
to send another 18x early media SDP offer.

Robert.

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