Chapter 22 VoIP Solutions: SIP : FortiGate VoIP solutions: SIP : Deep SIP message inspection : Configuring deep SIP message inspection : Discarding SIP messages with an unknown SIP message type
  
Discarding SIP messages with an unknown SIP message type
Enter the following command to discard SIP messages with an unknown SIP message line type as defined in all current SIP RFCs:
config voip profile
edit VoIP_Pro_Name
config sip
set unknown-header discard
end
end