 REFER, UPDATE Content-Length: 0 SIP: Understanding the Session Initiation Protocol 10.8 Call Setup Example with Two Proxies This section contains the complete message flow shown in Figure 2.2. INVITE sip:werner.heisenberg@munich.de SIP/2.0 Via: SIP/2.0/UDP 100.101.102.103:5060;branch=z9hG4bKmp17a Max-Forwards: 70 To: Heisenberg sip:werner.heisenberg@munich.de> From: E. Schroedinger <sip:schroed5244@aol.com>;tag= Call-ID: 10@100.101.102.103 CSeq: 1 INVITE Subject: Where are you exactly? Contact: <sip:schroed5244@pc33.aol.com> Content-Type: application/sdp Content-Length: 159 o=schroed5244 2890844526 2890844526 IN IP4 100.101.102.103 s=Phone Call C=IN IP4 100.101.102.103 m=audio 49170 RTP/AVP 0 a=rtpmap: PCMU/8000 INVITE sip:werner.heisenberg@200.201.202.203 SIP/2.0 Via: SIP/2.0/UDP proxy.munich.de:5060;branch=z9hG4bK83842.1 Via: SIP/2.0/UDP 100.101.102.103:5060;branch=z9hG4bkmp17a Max-Forwards: 69 To: Heisenberg <sip:werner.heisenberg@munich.de> From: E. Schroedinger k<sip:schroed5244@aol.com>;tag=42 Call-ID: 10@100.101.102.103 CSeq: 1 INVITE Contact: sip:schroed5244@pc33.aol.com> Content-Type: application/sdp Content-Length: 159 o=schroed5244 2890844526 2890844526 IN IP4 100.101.102.103 s=Phone Call C=IN IP4 100.101.102.103 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap: PCMU/8000 SIP/2.0 180 Ringing Via: SIP/2.0/UDP proxy.munich.de:5060;branch=z9hG4bK83842. ;received=100.101.102.105 Via: SIP/2.0/UDP 100.101.102.103:5060;branch=z9hG4bKmp17a To: Heisenberg ip:werner.heisenberg@munich.de>;tag=314159 From: E. Schroedinger <sip:schroed5244@aol.com>;tag=42 Call-ID: 10@100.101.102.103 CSeq: 1 INVITE Call Flow Examples Contact: : <sip:werner.heisenberg@200.201.202.203> Content-Length: 0 SIP/2.0 180 Ringing Via: SIP/2.0/UDP 100.101.102.103:5060;branch=z9hG4bKmp17a To: Heisenberg ip:werner.heisenberg@munich.de>;tag=314159 From: E. Schroedinger <sip:schroed5244@aol.com>;tag=42 Call-ID: 10@100.101.102.103 CSeq: 1 INVITE Contact: ksip:werner.heisenberg@200.201.202.203> Content-Length: 0 SIP/2.0 200 OK Via: SIP/2.0/UDP proxy.munich.