e providers, and the public (e.g. NRAs in the telecom- munications/ICT area). SDOs, such as the ITU, the European Telecommunications Standards Institute (ETSI), or the IETF, have collective knowledge and expertise with respect to QoS and QoE. Because QoS and QoE are always considered end-to-end (between the endpoints of the communication call or session), there are required global standards on QoS mat- ters. However, SDOs are seeing an increase in the number of cases where some parties decide to rely on industry standards relating to QoS/QoE instead of globally recognized standards. Regarding global standards, for example, ITU-T develops recommendations on performance, QoS, and QoE for all terminals, networks, and services, ranging from circuit-switched traditional telecom networks and services to multimedia applications over fixed or mobile IP-based networks. Table 1.3 gives examples of certain important ITU-T recommendations on QoS and QoE matters from different recommendation 1 Introduction Table 1.3 Some important ITU-T recommendations on QoS and QoE. ITU recommendation series Example ITU-T recommendations on QoS/QoE E-Series: Overall network operation, E.800: Definition of terms related to quality of telephone service, telephone operation, service and human factors E.802: Framework and methodologies for the determination and application of QoS parameters E.803: Quality of service parameters for supporting service aspects E.804: QoS aspects for popular services in mobile networks E.807: Definitions and associated measurement methods of user-centric parameters for call handling in cellular mobile voice service Supplement 9 to E-series: Guidelines on regulatory aspects of QoS G-Series: Transmission systems and G.1000: Communications quality of service: A media, digital systems and networks framework and definitions G.1010: End-user multimedia QoS categories G.1011: Reference guide to quality of experience assessment methodologies P-Series: Terminals, subjective and P.10/G.100: Vocabulary for performance and obj