GPRS Tunnelling Protocol (GTP) is an IP -based protocol that carries session information between nodes within a Mobile network.
GTP consists of three separate sub-protocols, GTP-C, GTP-U and GTP'. GTP-C is used between SGSN and GGSN in 3G and between SGW and PGW in 4G to create, modify and delete sessions or PDP contexts.
GTP-U is used between the RAN and the core network to carry the user-plane (U-plane) IPv4 or IPv6 data from the UE.
GTP' (GTP prime) is used between the CDF and CGF to carry charging information.
GTP uses either UDP or TCP transport protocol and there are different versions including v0, v1 and v2.