Packet sanity checking
The FortiOS Carrier firewall checks the following items to determine if a packet confirms to the UDP and GTP standards:
• GTP release version number — must be 0, 1, or 2
• Settings of predefined bits
• Protocol type
• UDP packet length
If the packet in question does not confirm to the standards, the FortiOS Carrier firewall drops the packet, so that the malformed or forged traffic will not be processed.