Chapter 4 FortiOS Carrier : ­­­­Overview of FortiOS Carrier features : GTP basic concepts : Billing and records
  
Billing and records
A major part of the GPRS network is devoted to billing. Customer billing requires enough information to identify the customer, and then billing specific information such as connection locations and times, as well as amount of data transferred. A modified form of GTP called GTP’ is used for billing. The home location records and visitor location records store information about customers that is critical to billing.