 request. The UPF can duplicate packets in the downlink and eliminate them in the uplink direction in the GTPU layer. It supports TSSS steering functionality to steer MA PDU session traffic. The PCF The PCF is responsible for providing a unified policy framework to govern network behavior. It provides policy rules to control plane functions such as the SMF SO that they can be passed on to the UPF to enforce them. It also accesses subscription information from a Unified Data Repository (UDR) to 5G network concepts make relevant policy decisions. It accesses the CHF for usage monitoring information, based on which it sends rules to the SMF. Hence, the PCF is used to manage the network QoS and traffic steering rules. NWDAF Figure 2.7 - PCF reference points It interacts with the AF over N5 and receives application-level information, such as the bandwidth and QoS requirements, and also takes a decision on traffic routing based on application traffic properties. The PCF interacts with the UDR; it retrieves policy and subscription information. The UDR can also send notifications based on subscription information changes to the PCF SO that it can in turn notify the SMF with updated rules for traffic policing. N30 interfaces with the Network Exposure Function (NEF); it exposes the capabilities, services, and resources of the PCF to the outside world. The N28 interface of the PCF with the CHF is leveraged for usage control, to notify the PCF when the subscriber crosses a usage threshold and needs to be throttled, as an example. When a threshold is breached, the CHF notifies the PCF, which, in turn, sends throttling rules to the SMF to be enforced on the UPF. The AMF and the PCF exchange UE mobility-related information SO that the PCF can trigger policies based on RAT type, UE mobility, and SO on. The NEF The NEF is responsible for securely exposing the NF capabilities and events to third-party AFs. The NEF stores information to and retrieves information from the UDF located in the same PLMN and securely provides informatio