Gi, SGi Interface (The EPS/EPC Interface)

The SGi interface connects the PGW to a external network (PDN), and the Gi interface connects the GGSN to a external network (PDN). The interface is based on the IP packet (user data/payload/data plane), possible also enabling exchange of signaling (ex. OSPF, BGP etc.). The interface can connects to the Radius server if Remote Access Dial-In User Service (Radius) is used.

The implementation Gi, SGi Interface in real topology network. All IP various packet combine in one routing table (virtual-router or routing-instance). It's possible to enable dynamic routing protocol (OSPF, BGP) for advertise PGW/GGSN IP address to external network. Usually PGW/GGSN can enable minimum basic OSPF. And also possible to enable redundancy mechanism like VRRP for multiple node.

Please refer to The EPS Interface.