GGSN (Gateway GPRS Support Node)
Updated
The GGSN is the gateway between a 2G or 3G mobile network and external data networks: it assigns the device’s IP address and routes its traffic according to the APN. It is defined in 3GPP TS 23.060, and its 4G equivalent is the PGW.
In practice
Many network diagrams and SIM documents still say GGSN for the gateway of a private APN, even when the traffic is 4G and the gateway is a PGW.