can no longer be guaranteed for a QoS flow. UPF, providing packet buffering and downlink data notification triggers. Charging Data Records (CDRs). Event Data Records (EDRs). Additionally, the new generation of SON can use application-specific performance indica- tors provided by the client in the UE, for example a video player. A standard for collection of this information is under development in 3GPP (3GPP TS 28.405). Another source of application-specific performance data could be the application servers such as video stream- ers, for which northbound APIs defined in 3GPP TS 23.222 can be utilized. Another important part of the 5G E2E SON support is the network data analytics func- tion (NWDAF), which collects network data and may be hosting analytics applications for analysis of the collected information. The NWDAF makes the raw information and output of the analytics available to any NF, including SON. For example, there can be an analytics application computing the load level for a particular NSI, with input collected at the NFs and possibly transport network links constituting the NSI. The NWDAF capabilities can be used for optimization of services provided to end users, with or without slicing. When slic- ing is deployed, optimization of business-to-business-to-customer (B2B2C) services such as "Slice as a Service" and "NSSI as a Service" is important to make slicing commercially successful. 6.5.9.5 Distributed SON In addition to the C-SON described above, which is the main focus of this section, NG-RAN also supports D-SON. In contrast to C-SON, D-SON does not require a centralized manage- ment entity and is typically implemented in a distributed fashion between NG-RAN nodes over control-plane network interfaces (e.g. Xn-C and NG-C). In Release-15, D-SON primarily enables dynamic configuration of Xn and NG interfaces, ANR, and network energy saving. It has been further enhanced in Release-16 to support Mobility Robustness Optimization (MRO) (intra and inter-system), mobility load balancing 6.5 Operations, 