[SIPForum-discussion] How does the SDP offer and answer works

[arun kumar]

Hi all
   Thankyou so much , iam clear now   ;-)


On 1/17/08, Mark Holloway <mh at markholloway.com> wrote:
>
>  If A is a media gateway and B is a SIP subscriber, usually the gateway
> will honor the preferred codec of the subscriber.    Thus meaning A is just
> informing B of what he is capable of, but if B responds with rtpmap: 8
> (G729) first and 0 (G711) second in the 200 OK, the call will be setup as
> G729a (unless B also states annexb=yes, then it will be G729b).
>
>
>
> *From:* discussion-bounces at sipforum.org [mailto:
> discussion-bounces at sipforum.org] *On Behalf Of *arun kumar
> *Sent:* Thursday, January 17, 2008 2:32 AM
> *To:* discussion at sipforum.org
> *Subject:* [SIPForum-discussion] How does the SDP offer and answer works
>
>
>
> Hi can any one can guide me in this
>
>
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>
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>        A---------INVITE/SDP----------> B
>
>
>
>       The SDP offer  has the following
>
>                 m= audio 49170 RTP/ AVP 0 8
>
>               a= rtpmap: 0 PCMU/8000
>
>              a= rtpmap: 8 PCMA/8000
>
>                    m= video 49172 RTP/AVP 32
>
>                    a= rtpmap: 32 MPV/90000
>
>
>
>     A<-----------200OK-------B
>
>
>
>                 B also supports all the media and codec types provided in
> the SDP offer of A
>
>
>
> So what will be the SDP answer of B, will it send all the medai and codec
> supported by itself ?
>
>
>
> my question is who will select the media & codec for the Media session
> establishment between  A & B, if more than  1 suitable codec matches between
> the endpoints which codec is selected and on what basis is it done.
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> v = 0
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> --
>
> With Regards
>
> Arun Kumar .P
>
>


-- 
With Regards
Arun Kumar .P
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