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> Chapter 33 - VoIP Solutions: SIP > The SIP session helper

The SIP session helper

The SIP session-helper is a high-performance solution that provides basic support for SIP calls passing through the FortiGate by opening SIP and RTP pinholes and by performing NAT of the addresses in SIP messages.

The SIP session helper:

  • Understands SIP dialog messages.
  • Keeps the states of the SIP transactions between SIP UAs and SIP servers.
  • Translates SIP header and SDP information to account for NAT operations performed by the FortiGate.
  • Opens up and closes dynamic SIP pinholes for SIP signalling traffic.
  • Opens up and closes dynamic RTP and RTSP pinholes for RTP and RTSP media traffic.
  • Provides basic SIP security as an access control device.
  • Uses the intrusion protection (IPS) engine to perform basic SIP protocol checks.