on Management (SM) messages between the SMF and the UE. An AMF uses the N14 interface for AMF re-allocation for AMF-AMF information transfer. This can either intra- or inter-PLMN, and therefore be leveraged for both inter- and intra-PLMN mobility. Additionally, to implement SMS functionality, it provides transport between the UE and the SMSF. 5G network concepts The SMF The SMF is responsible for session establishment, modification, and release. It is responsible for maintaining the tunnel between the UPF and the access node (the gNB). One of the most important responsibilities of the SMF is UE IP address allocation and management. This UE IP address can be locally allocated from a pre-configured IP pool, or it can be received from the UPF or an external data network. The SMF is expected to perform DHCPv4 and DHCPv6 server and client functionalities. It is responsible for responding to Address Resolution Protocol (ARP) requests and IPv4/IPv6 neighbor solicitation requests based on the local cache for Ethernet Protocol Data Units (PDUs). The SMF responds to ARP and neighbor solicitation requests by providing the MAC address corresponding to the IP address sent in the request: Figure 2.5 - SMF reference points SMF selects the UPF that will service the subscriber, and this selection can be based on various parameters, such as the current load on the UPF, the TAC, or cell ID-based selection for closer proximity to the UE. It is responsible for providing traffic steering information to the UPF SO that traffic is routed to the proper destination. It interacts with the PCF via the N7 interface and receives traffic rules and QoS parameters for each subscriber. The SMF also provisions lawful intercept probes for law enforcement authorities. It is responsible for collecting charging data and providing it to the CDF for billing purposes. The SMF is also the termination point for SM parts of NAS messages. It provides support to downlink data notification messages and notifies the AMF of any incoming traffic for a particular 