How GTP works
GTP performs the following tasks:
- Transmission of signals between GGSN and SGSN, which allows activation and deactivation of connection sessions on behalf of a user; as well as parameters setup and session renewal for a subscriber.
- Transmission of users data in GPRS base network between base network and radio access network. Transport in packets is possible in any protocol – IPv4, IPv6 or PPP.
- Delivery of information on consumed chargeable services to a billing center for subsequent invoice generation.
How GTP works in GPRS
For GPRS it’s the main protocol in use. It allows subscribers’ connection to the Internet from one spot in GGSN, even if subscribers are constantly on the go.
This also allows providing several VoLTE (Voice over LTE) types of services on the same device. GTP is the critically important tunnelling protocol – which is irreplaceable in all modern mobile networks.
GTP can be used with UDP or TCP protocols. Three GTP releases exist – 0, 1 and 2. GTP v.1 is used for UDP only. In v.0 the signaling protocol is united with the tunneling protocol on one port. V.1 and 2 are essentially two protocols: one for control (GTP-C), the other for user data tunneling (GTP-U).
Initially GTP was standardized in ETSI framework (GSM 09.60 standard). When UMTS standards emerged, GTP was moved to 3GPP, which supports it as 3GPP 29.060 standard since 2005. GTP uses the same messages format, but its application specifics are defined in 32.295 standard, together with the standardized formats for data transfer on fee charges.