On 8/4/14 10:12 AM, Sourav Dhar Chaudhuri wrote:
Hi,
Is there any way when a answered call [ 200OK is already provided for
initial INVITE and ACK also sent] can be transferred without using REFER method?
If it is possible without REFER then please let me know required procedure.
More detail is needed to answer this.
Lets assume that Alice and Bob are in a call. You want a transfer, so
let's assume the transfer target is Charlie.
Further, assume it is Alice that wants to initiate the transfer,
resulting ultimately in Bob talking to Charlie.
A simple answer to your question is for Alice to initiate the call to
Charlie, and then bridge the media between Bob and Charlie. It is also
possible for Alice to use 3pcc O/A techniques to establish a direct
*media* path between Bob and Charlie, while Alice remains in the
signaling path between them.
The reason for REFER is to get Alice out of the signaling path. If there
is a middlebox in the signaling (e.g. a sip pbx or an SBC) then in
principle Alice can ask that middlebox to handle the transfer. But Alice
needs a way to convey the desire to do so. Often REFER is still used for
that, but is intercepted by middlebox, which then uses mechanisms such
as I described above. Some other mechanism, other than REFER, can be
used for that but it will be a proprietary solution.
Does that help?
Paul
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