SIP/2.0 404 Not Found
Via: SIP/2.0/UDP nm;branch=foo;rport=26810;received=224.124.137.4
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=EFC5EE7F4A683C99
Call-ID: 50000
CSeq: 42 OPTIONS
User-Agent: FRITZ!OS
Content-Length: 0