SIP/2.0 200 ok
Via: SIP/2.0/UDP nm;received=224.92.194.224;branch=foo;rport=26810
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=385f31da9b19c6fc32661938310090ec.fe3b
Call-ID: 50000
CSeq: 42 OPTIONS
User-Agent: reg-b1
Content-Length: 0