SGW-C Serving Gateway Control plane function
The SGW-C controls the functionality performed by the assigned SGW-U when control and user plane separation is in place. A subscriber is served by a single SGW-C, and can have multiple SGW-Us selected for multiple PDN connections. When the subscriber moves around the E-UTRAN, under control of a SGW-C their point of attachment to the EPC remains fixed at the SGW-U (unless the network decides that a SGW-U relocation is required). Additional responsibilities include lawful interception of subscriber traffic, as well as triggering downlink data buffering whilst the subscriber is paged and PGW pause of charging management based on implemented policies (failed paging, abnormal radio link release and dropped packets/bytes at SGW-U).
