In the core network (EPC), the UMTS equivalent SGSN has been split into MME (Mobility Management Entity), which handles control functions, and Serving SAE GW (eAG), which handles U plane traffic. There is one anchor MME and eAG per UE. MME and eAG may be collocated.
The UMTS GGSN equivalent is PDN SAE GW (P-GW), which may or may not be collocated with Serving SAE GW. The P-GW is the inter-system anchor point for each UE. It provides access to PDNs.