Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS)

The NAS protocol is used on the control plane between the UE and the core network, the MME (Mobility Management Entity). The NAS layer is handling mobility related functions between the UE and the core network, like attach and tracking area update, authentication and security. It is also responsible for establishing and maintaining IP connectivity between the UE and the core network.