A.3 Blind call transfer with third party call control

24.6293GPPExplicit Communication Transfer (ECT) using IP Multimedia (IM) Core Network (CN) subsystemProtocol specificationRelease 18TS

An example of a call flow where a media server is used is given in figure E.1 of 3GPP TS 24.628 [10]. In this call flow, the media server is involved in the media path before transfer is received and remains involved after the call is transferred. For blind communication transfer, the media server may be connected only to the transferee (UE-B) after the REFER request is received and be disconnected when the transfer target accepts the call.

An example of call flow where no media server is used is given in figure E.1 of 3GPP TS 24.628 [10].