Hello,
 
In case an Offer modification is issued after a previous modification was 
rejected (e.g. re-INVITE answered with 488), should SDP version number increase 
by 1 wrt the previous Offer? Or should it increase by 1 wrt the SDP for which 
the Offer/Answer model was closed before the first re-INVITE?
 
Extract from RFC 3264:
 
When issuing an offer that modifies the session,
   the "o=" line of the new SDP MUST be identical to that in the
   previous SDP, except that the version in the origin field MUST
   increment by one from the previous SDP.
 
The offer/answer exchange is atomic; if
   the answer is rejected, the session reverts to the state prior to the
   offer (which may be absence of a session).

Extracts from RFC 6337:
 
In the "o=" line, only the version number may change, and if it
      changes, it must increment by one from the one previously sent as
      an offer or answer.
 
I'd say that the "previous SDP" is the one that is currently in place for the 
session, therefore as the first Offer has been rejected, the same version 
number (already incremented by 1) can be kept in next re-INVITE. Has this been 
addressed somehow?
 
Thanks for your support.
 
Paolo
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