[SIPForum-discussion] Early media...Use.

[Naresh Parmar]

Yes, early media in fact is exchange of sdp parameters through 183 session
progress message before getting the final 200 OK message. One typical use of
it would be to play a music for the calling party by the proxy server
whenever it sees a call by a given party. So that means when the call is in
progress (i.e. ringing at the called party), the calling party hears the
music as decided by the proxy server as there is an early media session
established between the proxy and the calling party. When the called party
eventually answers the call, the early media session is closed and the final
sdp exchange happens between the calling party and the called party (as in
the 200 OK message), based on which media streams are opened.

 Another use of early media would be to have a complete session description
exchanged through 183 session progress message between the calling and the
called party, and open the media stream immediately after getting the 200 OK
response (200 OK does not carry sdp normally in this case as its already
been conveyed through the 183 session progress), this avoids processing the
sdp after receiving 200 OK and thus establishes the call more quickly.

No, early media is not necessary unless you have some specific requirements
to do so.
Hope this helps.


On 2/2/07, nithya kumar <nithyakr at huawei.com> wrote:
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> Hi Sip Experts,
>
>               Can some one explain the exact use of Early media ?????
> …Early media is nothing but exchange of SDP parameter Before call
> Begins(means Dialog begins)…if so Re-invite to both Caller and callee before
> call starts (dialog starts) also doing SDP exchange functionality….!!!! …
>
> --- if so exact use of early media????
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> -- early media is compulsory ??
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> Nithya Kumar.R
>
> Huawei Technologies India Pvt Ltd,
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> Bangalore
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> Mob-9986035813
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