ors, and end-users. Most important QoS parame- ters, which describe the service requirements and can be measured and understood by the end-user (i.e. the customer), are referred to as key performance indicators. There are service dependent QoS parameters and hence service dependent KPIs, as well as service independent QoS parameters (e.g. mobile network radio coverage) and hence service independent KPIs. All selected technical QoS parameters as KPIs are subject to measurements, which can be performed by all parties in the value chain. 7.1 QoS, QoE, and Application Needs In the all-IP world each service includes an application (e.g. VoIP is a service that uses voice application running on the top of RTP/UDP/IP protocol stack). The relationship between network layer QoS and the obtained QoE (this refers mainly to services used by humans) is strongly dependent on the given service and its application. The following are typical examples regarding QoS requirements of some services (Figure 7.1): Email is delay tolerant but requires lossless transmission on the application layer (e.g. email client to email server communication). Lossless communication is accom- plished with the use of TCP, which is possible due to email delay tolerance. The QoS for voice communication (such as in VoIP, i.e. telephony) mainly depends on packet delay, delay variation (jitter), and depends less on packet loss (because human ear is delay tolerant, can accommodate up to several percent of loss). Addi- tionally, voice QoE is impacted by terminal capabilities, various user-related aspects such as current mood, applied tariffs, and other factors that can have an influence. The well-known criterion for ensuring proper experience is that one-way delay for voice services should be below 150 ms for best performances, while delays above 400 ms are unacceptable for general network planning (however, there are exceptions when this upper limit will be exceeded, such as double satellite hop for locations that cannot be reached with terrestrial networks)