SIP/2.0 200 OK
Via: SIP/2.0/UDP nm;branch=foo;rport=26810;received=207.90.244.17
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=206374879
Call-ID: 50000
CSeq: 42 OPTIONS
User-Agent: SIP/2.0
Content-Length: 0