, many times it is more convenient to estimate QoE based on objective testing and using statistical estimation models for the QoE [11]. There are three modes of objective testing to evaluate QoE: intrusive mode (a signal is injected into the system under test in order to generate a degraded output signal), non-intrusive mode (the quality assessment is performed on the "live" user traffic is carried by the network, without generation of active test signals), and planning mode (it is not used in real-time environment, but it is used for the planning and design of ICT systems). Of course, all QoS parameters are measured with objective measurements. Certain quality indicators such as call set-up time, call success ratio, etc. can easily be measured by installing probe stations in appropriate locations. Then, quality measure- ments can be made on real user traffic or by using artificially generated traffic from/to probe network stations/nodes. Such approaches can be used on both public Internet network or managed IP networks. The purpose of quality assessment via measurements is to perform analysis and evaluation of the service or network performances and to take corrective or proactive actions where it will be found necessary (based on QoS/QoE analysis with perfor- mance measurements). The same service provided by a telecom operator can be measured by the service provider and perceived by the customer (two views), as shown in Figure 7.10. In addition to definitions and standards regarding QoS parameters and their assess- ments, measurements need to be defined SO they will be practical for operators (e.g. measurements are typically the basis for networks and services design and optimiza- tion) and important to customers (e.g. can be used for comparison of QoS provided by concurrent operators in a given country, or can be used to check/validate whether contracted QoS level in the SLA is supported by the service provider). 7.8 Broadband QoS Measurements Quality of Service (QoS) provided Customer perception Internal Serv