Nebojsa Miljanovic wrote:
> Trying to get a feel on how various developers interpret RFCs 3261, 3262 and
> 3264.
>
> If you are acting as an UAC and you have received SDP in reliable 18x response
> (i.e. PRACK was used), and then again that same SDP comes in 2xx, what will
> you do?
>
> 1. Verify that 18x and 2xx SDPs are the same and accept it.
>
> 2. Tear down the call since you consider SDP in 2xx as an invalid Offer.
You should not tear down the call, because including SDP in this way is
legal. If present, it is supposed to be the same as what was in the
reliable provisional. So you could compare them to see that they are in
fact the same. If they are not the same then a protocol violation has
occurred. At that point its not at all clear which of the SDPs is the
valid one, so you *might* want to tear down the call. (If you don't, you
have a 50/50 chance of getting it right.)
The situation gets more muddy if there has been an additional
offer/answer exchange. I.e.:
-> INVITE w/sdp1 offer
<- 180 (invite) w/sdp2 answer
-> PRACK
<- 200 (prack)
-> UPDATE w/sdp3 offer
<- 200 (update) w/sdp4 answer
<- 200 (invite) w/sdp5
-> ACK
The question here is whether sdp5 should be the same as sdp2, or sdp4.
It seems that it should be the same as sdp2 but there is certainly some
logic that might suggest sdp4 though afaik there is no normative
language to support this. I have heard reports that various servers
actually do this.
Paul
> Also, do you know of any UAs that require 2xx to contain SDP even after
> Offer/Answer was done with 183/PRACK.
>
> Thanks.
>
>
>
>
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