T-Lib-Initiated SingleStepTransfer REFER

Description

UA1 calls UA2, and the T-Lib request transfers the call from UA2 to UA3.

This scenario is equivalent to a single-step transfer using the REFER method executed from UA2, except that in this case, the REFER message originates on SIP Server, not on UA2. Also, the "202 Accepted" message comes back to SIP Server, not UA2, and SIP Server also disconnects the call between UA1 and UA2 using a third-party call control release.

Diagram