SIP: Call Forwarding UnconditionalAliceProxyBobGatewayAliceProxyBobGatewayBob has set call forward.[01]INVITE[02](100 Trying)[03](181 Call Is Being Forwarded)Note that the 181 Call is Being Forwarded response isshown as sent by the proxy. Strictly speaking, theproxy is behaving as a user agent in this case as aproxy cannot generate non-100 provisional responses.The proxy server rewrites Bob's forwarded Request URIand sends INVITE.[04]INVITE[05]180 Ringing[06]180 Ringing[07]200 OK[08]200 OK[09]ACK[10]ACKBoth Way RTP[11]BYE[12]BYE[13]200 OK[14]200 OKRFC5359: Call Forwarding Unconditional