SIP: Call ParkAliceBobPark ServerCarolAliceBobPark ServerCarol[01]INVITE[02]180 Ringing[03]200 OK[04]ACKBoth Way RTPBob Parks callBob REFERs Park Server to establishsession with Alice, which replaces theestablished session between Alice andBob. Note that there is no sessionestablished between Bob and the ParkServer.[05]REFER Refer-To: A[06]202 Accepted[07]NOTIFY 100 Trying[08]200 OKPark Server places call to Alice to replacesession between Alice and Bob.[09]INVITE Replaces: B[10]200 OK[11]ACKRTP Music[12]BYE[13]200 OKPark Server reports success back to Bobby returning a 200 OK response. Bobobtains the dialog identifiers from theheaders included in the response.[14]NOTIFY 200 OK[15]200 OKAlice is now parked at the Park Server.Carol picks up the callCarol picks up the call by sending anINVITE to A, which replaces the existingsession with the Park Server. Carol needsto know the dialog information to constructthe Replaces header.[16]SUBSCRIBE[17]200 OK[18]NOTIFY (dialog-info)[19]200 OK[20]INVITE Replaces: Park Server[21]200 OK[22]ACKBoth way RTP MediaAlice replaces the session to the ParkServer with the new session with C andgenerates a BYE to disconnect the ParkServer.[23]BYE[24]200 OKNo more RTP MusicRFC5359: Call Park