PPTP

PPTP:
  Firmware: 1
  Hostname: sxxa3
  Vendor: MikroTik

SIP/2.0 404 Not Found
From: <sip:nm@nm>;tag=root
To: <sip:nm2@nm2>;tag=bd3f80-0-13c4-50029-26d73-52d4f4e6-26d73
Call-ID: 50000
CSeq: 42 OPTIONS
Via: SIP/2.0/UDP nm;received=224.108.106.189;rport=26810;branch=foo
Supported: replaces,100rel,timer
Accept: application/sdp
Allow: INVITE,ACK,CANCEL,BYE,OPTIONS,REFER,INFO,NOTIFY,PRACK,MESSAGE
Content-Length: 0