2020/05/20 11:43:13.411356 4.5.6.40:1029 -> 1.2.3.14:5060 NOTIFY sip:1.2.3.14 SIP/2.0 Via: SIP/2.0/UDP 192.168.15.177:5568;branch=z9hG4bK-7ef72342 From: "Test" ;tag=7b97cf77697b5442o0 To: Call-ID: 7faf6ebb-69449dce@192.168.15.177 CSeq: 31305 NOTIFY Max-Forwards: 70 Event: keep-alive User-Agent: Linksys/SPA941-5.1.8 Content-Length: 0 2020/05/20 11:43:13.411521 1.2.3.14:5060 -> 4.5.6.40:5568 SIP/2.0 400 Missing Contact header Via: SIP/2.0/UDP 192.168.15.177:5568;received=4.5.6.40;branch=z9hG4bK-7ef72342 Call-ID: 7faf6ebb-69449dce@192.168.15.177 From: "Test" ;tag=7b97cf77697b5442o0 To: ;tag=z9hG4bK-7ef72342 CSeq: 31305 NOTIFY Server: Asterisk PBX Content-Length: 0