OPTIONS sip:[2001:db8::10] SIP/2.0
To: sip:user@example.com
From: sip:user@example.com;tag=81x2
Via: SIP/2.0/UDP [2001:db8::9:1];received=2001:db8::9:255;branch=z9hG4bKas3
Call-ID: SSG95523997077@hlau_4100
Max-Forwards: 70
Contact: "Caller" <sip:caller@[2001:db8::9:1]>
CSeq: 921 OPTIONS
Content-Length: 0

