Вот дебаг общения с мультифоном:
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.10.3:5060;branch=z9hG4bK-393637-7ac96254cb46871fb03bf9448d79b01a;received=192.168.10.3
From: "1000" <sip:1000@192.168.10.9>;tag=b43aa2a5
To: "1000" <sip:1000@192.168.10.9>;tag=as23310d70
Call-ID ...

