in Chapter 7 of this book). Regarding the practices used in different countries [2], active measurement is most widely used by the NRA for QoS measurements (e.g. for broadband IAS). With active measurement methods NRAs can produce comparable reports from measure- ments on national telecom operators on a regular basis. Yet active measurements impose additional costs, including the following: Costs for deployment of measurement systems for active measurements, such as soft- ware and hardware probes and centralized servers and databases for processing and reporting of the collected measurement data. For the purposes of comparison of QoS performance of different telecom operators, the sampling methodology can be critical to provide comparable (i.e. benchmarking) results from QoS measurements on different operators' networks. The measurement results are used by the NRA for auditing QoS. The auditing process is based on aggregated results, not on individual customers. However, there are differ- ent possibilities of aggregation of QoS measurements per service (IAS, voice, etc.). The aggregation can be per geographic region, per type of area (urban, rural, highways, and railways), per subscriber types (business and residential). How aggregation of the results will be used can be decided on a case-by-case basis by taking into account various local circumstances and quality problems. 9.6 KPIs and Measurement Methods for Fixed and Mobile Services Most important QoS parameters are referred to as KPIs, and they are the subject of QoS regulation. KPIs are internal indicators which are based on network performance. Typically, KPIs are based on network counters and are essential for operation and main- tenance as well as telecom business models. Also, KPIs can be reported and audited, but they are meaningless if used out of context. In the IP-based networks (that is IAS, VoIP, IPTV, or other services), besides service availability and bitrates (for the IAS), the important KPI is end-to-end delay, which has a major influence on t