OPTIONS sip:user@[2001:db8:::192.0.2.1] SIP/2.0
To: sip:user@[2001:db8:::192.0.2.1]
From: sip:user@example.com;tag=810x2
Via: SIP/2.0/UDP lab1.east.example.com;branch=z9hG4bKas3-111
Call-ID: G9559905523997077@hlau_4100
CSeq: 689 OPTIONS
Max-Forwards: 70
Content-Length: 0
