echnologies). The global Internet infrastructure consisting of interconnected ASs is crucial in understanding why the traditional way of QoS implementation and enforcement (that is, the same approach in all countries, e.g. for digital telephony, i.e. PSTN/Integrated Services Digital Network (ISDN)) is no longer possible in an IP-based environment. Why? Because in IP environments there is heterogeneity of various IP networks, variety of applied network and traffic management techniques, and the plethora of services and applications which are constantly being offered (e.g. huge OTT applications/services ecosystems, with millions of applications). So, one may note that the QoS as an end-to-end characteristic is becoming more complex in the telecommunications/ICT completely based on Internet networking and Internet technologies. How is QoS transitioning from the traditional telecom world (made for telephony and TV) to the all-IP world? It is based on strict standardization of certain functions and certain protocols. For example, the traditional telecommunication approach by default includes end-to-end QoS support in the network. Also, signalization in a standardized manner is required for establishing calls/sessions between any two ends on any two devices connected to any two networks regardless of the types of application, device, or network. That led to implementation of certain functions and approaches from the tra- ditional telecom world in the Internet networks, which were initially best-effort based. The main standardization for such convergence was carried by the ITU in its umbrella of specifications called next generation networks (NGNs), which initially started as an idea around 2003. One of the main purposes of the NGN standardization framework was (and still is) to standardize the end-to-end QoS support in all-IP networks (includ- ing all needed functions in transport and service stratums) that is essential for real-time services, such as VoIP (voice over Internet protocol) and IPTV (Internet protocol tele