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RE: [reSIProcate] dum: ACK retransmission issues and sending reINVITEwith no offer


If we send an initial invite w/out an offer, causing late media in the ACK,
we will need to retransmit that answer in the ACK.  

If we do a re-invite, we store the offer in mProposedLocalSdp, so we still
have the ability to retransmit the answer stored in mLocalSdp, until the
re-invite finishes.

If we do yet another re-invite and receive a 200 for the first we won't be
able to respond with the correct SDP, but there is something severely wrong
if this is happening, and that SDP should have no meaning at this point.

We would have to store whether or not late media should be sent w/ a
particular ACK retransmission.

--Derek

> -----Original Message-----
> From: resiprocate-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:resiprocate-
> devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jason Fischl
> Sent: Friday, November 19, 2004 12:38 PM
> To: resiprocate
> Subject: [reSIProcate] dum: ACK retransmission issues and sending
> reINVITEwith no offer
> 
> We have been implementing the new InviteSession. The following issue
> came up:
> 
> In the previous implementation the InviteSession stored all ACK messages
> that were sent in order to retransmit the appropriate one when a 200 was
> received in the Connected state. This was necessary since a second
> reINVITE could occur while the first 200 was still being retransmitted.
> 
> In the new implementation, we decided that storing the ACK messages was
> unnecessary. We can build the ACK from the 200/INVITE using the dialog
> and fill in the CSeq sequence number from the 200. This works because
> dum doesn't allow a reINVITE with no offer. We couldn't think of a good
> use case for this. However, we do allow a dum UAS to receive a reINVITE
> with no offer.
> 
> In the b2bua case, if the b2bua receives an INVITE with no offer from
> some confused gateway, it can respond with the current session
> description and then deal with the answer when it arrives.
> 
> It is worth discussing further whether there are any valid use cases for
> dum sending a reINVITE with no offer - b2bua or otherwise.
> 
> Jason
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