SIP/2.0 404 Not Found
Via: SIP/2.0/UDP nm;branch=foo;received=224.170.186.113;rport=26810
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=as3b524a65
Call-ID: 50000
CSeq: 42 OPTIONS
Server: Teleco Telephone Proxy Agent
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INF...