Hi Everyone, 

I was faced with the following question, while working on issues related to 
inconsistency of SDP "o=" line and call forking. 
E.g. say we have Alice and Bob, both are UAs. 

Alice initiates a call to Bob by sending of INVITE w/SDP Offer, but Alice 
doesn't support UPDATE&PRACK (doesn't matter why). 
Bob would like to provide a kind of early media, so it sends media capabilities 
with forked 18x (180/183) responses.

So, we have the following call flow: 

Alice                    Bob
       INVITE w/SDP0
   ---------------------->
....

     180 w/SDP1, to-tag=1
   <----------------------
     183 w/SDP2, to-tag=2
   <----------------------
....
   200 OK w/SDPn, to-tag=n
   <----------------------

So, here we have multiple SDP Answers sent within different SIP dialog.
The question is: What should be the "o=" line of each SDP Answer? Should it be 
unique for each dialog?

Thanks in advance,
-----------------
Aleksey Entsov
mailto:[email protected]
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