 via a stand-alone non-3GPP access, multiple N1 instances could exist for the UE, that is, there is one N1 instance over NG- RAN and one N1 instance over non-3GPP access [3]. 1.2.2.2 PDN Sessions and 5GC Identifiers In an LTE network, once a UE connects to a PDN using the IP address assigned to it upon successful initial attach to the network, the IP connection remains in place after a default EPS bearer is established over the LTE network and until the UE detaches from the LTE network (i.e., the PDN connection is terminated). Even when there is no user traffic to send, the default EPS bearer always stays activated and ready for possible incoming user traffic. Additional EPS bearers can be established, if the best effort QoS attributes of the default EPS bearer do not satisfy the service requirements. The additional EPS bearer is called a dedicated EPS bearer, where multiple dedicated bearers can be created, if required by the user or the network. When there is no user traffic, the dedicated EPS bearers can be removed. Dedicated EPS bearers are linked to a default EPS bearer. Therefore, IP traffic from or to a UE is delivered through an EPS bearer depending on the required QoS class 5G Network Architecture 147 over the LTE network. Uplink IP traffic is mapped from a UE to the EPS bearer while downlink IP traffic is mapped from a PGW to the EPS bearer. Each E-RAB is associated with a QCI and an allocation and retention priority (ARP), where each QCI is characterized by priority, packet delay budget (PDB), and acceptable packet loss rate. The 5G core network supports PDU connectivity service, that is, a service that provides exchange of PDUs between a UE and a data network. The PDU connectivity service is sup- ported via PDU sessions that are established upon request from the UE. The PDU sessions are established (upon UE request), modified (upon UE and 5GC request), and released (upon UE and 5GC request) using NAS session management signaling over N1 between the UE and the SMF. Upon request from an application serv