INVITE sip:[email protected] SIP/2.0 As we move further down the call flow, the actual voice call begins , using Realtime Transport Protocol (RTP) to move the voice stream. F17 ACK Proxy 2 -> B ACK ...

The SIP standard ... top of an SIP Proxy code base, which gives it a framework for its state machine, threads and call-processing data structure. The user presses A to activate the UA and Z to ...