Hi, 

>It can be the situation when the call originally is connected 
>to some media announcement server (connected - meaning 
>getting RTP, for example to play ringback), than - to the 
>final user. In that case the UAC has to switch from the media 
>in 18x SDP to the media in 200 SDP

It is not allowed, for the same dialog.

But, in your use-case you can use "fake forking" (see separte thread),
and use different To tags in the 18x and 200. Then the 18x (tag=x) can
be used for the announcement, and 200 (tag=y) be used for the UAS.

Regards,

Christer

> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf 
> Of Sanjay Sinha (sanjsinh)
> Sent: Wednesday, February 14, 2007 8:37 PM
> To: Nebojsa Miljanovic; [email protected]
> Subject: Re: [Sip-implementors] SDP in 2xx response after reliable 18x
> 
>  
> Option 2 does not seem correct. Option 1 is correct and you 
> may also want to ignore the sdp in 200 OK, just treat it as 
> if there was no sdp in 200 OK.
> 
> Sanjay
> 
> >-----Original Message-----
> >From: [EMAIL PROTECTED]
> >[mailto:[EMAIL PROTECTED] On Behalf 
> Of Nebojsa 
> >Miljanovic
> >Sent: Wednesday, February 14, 2007 12:30 PM
> >To: [email protected]
> >Subject: [Sip-implementors] SDP in 2xx response after reliable 18x
> >
> >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.
> >
> >
> >Also, do you know of any UAs that require 2xx to contain SDP 
> even after 
> >Offer/Answer was done with 183/PRACK.
> >
> >Thanks.
> >
> >
> >
> >
> >_______________________________________________
> >Sip-implementors mailing list
> >[email protected]
> >https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
> >
> 
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