Chapter 4 FortiOS Carrier : ­­­­Overview of FortiOS Carrier features : GTP basic concepts : Transport
  
Transport
Transport protocols move data along the carrier network between radio access and the Internet or other carrier networks.
FortiOS Carrier should be present where information enters the Carrier network, to ensure the information entering is correct and not malicious. This means a Carrier-enabled FortiGate unit intercepts the data coming from the SGSN or foreign networks destined for the SSGN or GGSN onto the network, and after the GGSN as the data is leaving the network.