[SIPForum-discussion] Is the preference codec 0 ?

[Vivek Batra]

Comments Inline in RED.
--VB

2008/8/27 雨 陈 <chen.yu26 at yahoo.com.cn>

> Hi All,
> there is a call flow of modifying session between two different softswitch:
> User A           User B
> |  RTP Established   |
> |<=============>|
>                    |  INVITE [SDP]       |  the offer SDP m= audio 9256
> RTP/ATP 8 0 97
>                    |------------------------>|
>                    |             100               |
>                    |<------------------------|
>                    |                                   |
>                    |       200 [SDP]          |  the answer SDP m= audio
> 10054 RTP/AVP 0
>                    |<------------------------|
>                    |            ACK             |
>                    |------------------------>|
>
> Well, according to RFC3264, the preference codec should be present at
> first. So, the User A would like to choose PT=8 (PCMA), while the User B
> just afford PT=0 (PCMU).
>

It is upto UAS policy how to select the desired PT.

>
> MY QUESTION IS:  Did they modify the session sucessfully? and if so, is the
> audio codec they  had negotiated  PT=0 (PCMU) ?
>

Yes. Session will modify successfully since both has been negotiated on
PT=0.

>
>
> Thanks & Regards
>
> Nora
>
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