request:
OPTIONS sip:test@sip.voice.google.com SIP/2.0
Via: SIP/2.0/UDP 192.168.99.53:42173;branch=z9hG4bK.00d58f7a;rport;alias
From: sip:sipsak@192.168.99.53:42173;tag=6d3a593c
To: sip:test@sip.voice.google.com
Call-ID: 1832540476@192.168.99.53
CSeq: 1 OPTIONS
Contact: sip:sipsak@192.168.99.53:42173
Content-Length: 0
Max-Forwards: 70
User-Agent: sipsak 0.9.6
Accept: text/plain


send to: UDP:74.125.95.192:5060

message received
received from: UDP:74.125.95.192:5060
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.99.53:42173;branch=z9hG4bK.00d58f7a;rport=54367;alias;received=62.131.6.55
From: sip:sipsak@192.168.99.53:42173;tag=6d3a593c
To: sip:test@sip.voice.google.com;tag=b6af3ec14a5583bc5e0a35f4053f902f.6701
Call-ID: 1832540476@192.168.99.53
CSeq: 1 OPTIONS
Server: OpenSIPS (1.6.2-notls (x86_64/linux))
Content-Length: 0