Rx- Interface between AF and the PCRF Functionality Rx reference point. Sbc- Interface between CBC and MME Functionality Warning message delivery and control functions.
S9 - Interface between Home PCRF and the Visited PCRF Functionality QoS policy transfer and charging control information. It supports local breakout function.
S11 - Interface between MME and Serving GW Functionality Reference point.
S12 - Interface between UTRAN and Serving GW Functionality GTP-U protocol is used to define this reference point for user plane tunnelling with Direct Tunnel.. Usage of S12 is an operator configuration
S13- Interface between MME and EIR. Functionality Enables UE identity check procedure.
Sgi - Interface between PDN GW and the packet data network. Functionality Packet data network interface for 3GPP accesses. 1. Operator external public 2. Private packet data network 3. Intra operator packet data network, e.g. provision of IMS services.