Chapter 4 FortiOS Carrier : Configuring GTP on FortiOS Carrier : Configuring Anti-overbilling in FortiOS Carrier : Anti-overbilling with FortiOS Carrier
  
Anti-overbilling with FortiOS Carrier
The Carrier-enabled FortiGate unit can be configured to assist with anti-overbilling measures. These measures ensure that the customer is only billed for connection time and data transfer that they actually use.
Anti-overbilling on the Carrier-enabled FortiGate unit involves:
the administrator configuring the overbilling settings in the GTP profile to notify the Gi firewall when a GTP tunnel is deleted
the unit clearing the sessions when the Gi firewall receives a notification from the Gn/Gp firewall about a GTP tunnel being deleted This way, the Gi firewall prevents overbilling by blocking traffic initiated by other users.
The three locations to configure anti-overbilling options include:
System > Network > Interface > Gi Gatekeeper — edit an interface, and enable to monitor Gi anti-overbilling traffic on this interface
System > Admin > Settings > Gi Gatekeeper Settings — set the context ID and port that anti-overbilling will take place on.
Security Profiles > Carrier > GTP Profile > Anti-Overbilling — the IP address, port, interface and context ID to use for anti-overbilling measures.
For detailed options, see “Anti-Overbilling options”.