GPRS Tunnelling Protocol (GTP) is a group of IP-based communications protocols used to carry General Packet Radio Service (GPRS) within Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) networks. It allows carriers to transport actual cellular packets over their network via tunneling. This tunneling allows users to move between SGSNs and still maintain connection to the the Internet through the GGSN.

GTP has three versions version 0, 1, and 2. GTP1 and GTP2 are supported by FortiOS Carrier. The only GTP commands that are common to all forms of GTP are the echo request/response commands that allow GSNs to verify up to once every 60 seconds that neighboring GSNs are alive.