[SIPForum-discussion] Early Media Call flow

[Stephen James]

My answer was wrong in that I said branch - I should have said to-tag. We have seen just such a scenario when the original call went to one device got ringback in early mediaand then transferred to voice mail on no-answer where the terminator and the voice mail had differentcodecs configured. Stephen James 
sjames_1958 at yahoo.com We are not princes of the earth, we are the descendants of worms, and any nobility must be earned.

      From: Paul Kyzivat <pkyzivat at alum.mit.edu>
 To: discussion at sipforum.org 
 Sent: Monday, May 11, 2015 11:35 AM
 Subject: Re: [SIPForum-discussion] Early Media Call flow
   
On 5/7/15 6:04 AM, Kamal Kandpal wrote:
> /Hi All ,
> //
> //I have come across one sceanrio :/
>
> /Invite sdp(O1)---------------------->
> //183 sdp V1(A1) <---------------------- PCMU codec , Audio port 2000/
>
> /Prack --------------------- >/
>
> /200 <----------------------
> //200 sdp V2 <---------------------------PCMA codec , Audio port 5000
> //ACK ------------------------------------->
> //
> //
> //Here Sdp coming in 183 and 200 is completely different and coming from different user Agent over same Call-id./

I presume that the 183 and first 200 have one to-tag, and the 2nd 200 
has a different to-tag.

Assuming that is right, then you have a forked invite that was answered 
by two forks. That is a valid case.

> //As offer answer is complete after 183 sdp ,how should we handle 200 coming with different sdp ?
> //1. Assuming 200 sdp as new offer and send answer in ACK ?
> //2. Ignore 200 sdp as offer answer already completed ?/

You have two independent dialogs. Your choices are:
- keep them both
- keep one and terminate the other one.
-- send a BYE (with the appropriate to-tag) to the one you
    want to terminate.

    Thanks,
    Paul

> /As per RFC 6337 SDP should not be included in subsequent response once offer answer has been completed./
>
> /Thanks/
>
> /Kamal/
>
> /
> /
>
>
>
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>

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