SIP protocol / call waiting

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First i would like to apologize for my bad english, I wish you will understand my problem. Here's my question, for my internship, I need to create a fonctionality that allows a caller to put his call in waiting, with a button, and to take the call back with that button again. And i think there's an option with SIP protocol that allows to do that, but i just can't find it, i searched in internet in some documentations, the only thing I might know and i'm not even sure is that it could be an option in a re-INVITE request, that can be send by the called or the caller one, if someone could help me ? Thanks

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Rajesh On

The feature you are looking for is achieved by implementing the Call Hold Scenario on a SIP Call.

there are 3 ways to put the call on hold at the press of the button.

  1. Generate a Re-INVITE SDP with SendOnly option - the answer shall contain a recvonly and in this case you can go ahead and inject hold music media through the rtp stream.

  2. Sending inactive in the Re-INVITE SDP which basically puts the media inactive for the session. This is when no rtp exchange is desired.

  3. Sending the 0.0.0.0 notation for the Re-INVITE SDP - This is the old deprecated format of call hold when IPV4 was still the norm [still is!!] but it makes sure the RTP doesn't have a ip to be sent.

All of these mechanisms rely on the basic methods and hence it shouldn't be very difficult to achieve using any client software.