es the dominant type of cloud service cate- gory is the SaaS). The efficient delivery of cloud services contributes to the development of the cloud computing market, which depends on the ability to build economies of scale. The establishment of a digital single market (that is, all ICT services to be on the same digital market with the same rules) is aimed toward unlocking the scale which is necessary for reaching the full potential of cloud computing services everywhere. Overall, QoS regulation for broadband services is targeted to help customers to make informed choices, to check claims by operators, and to understand the state of the digital market. However, the main challenges are to maintain or improve QoS and QoE in the presence or absence of competition in the ICT/digital services market. References 1 Janevski, T. (2014). NGN Architectures, Protocols and Services. Chichester: Wiley. 2 Janevski, T. (2015). Internet Technologies for Fixed and Mobile Networks. Norwood, MA: Artech House. ITU-T Recommendation Y.2261, PSTN/ISDN Evolution to NGN, September 2006. 4 ITU-T Recommendation Y.2262, PSTN/ISDN Emulation and Simulation, December 2006. ITU-R Recommendation BT.2020-2, Parameter Values for Ultra-high Definition Television Systems for Production and International Programme Exchange, October 2015. References 6 ITU-T Recommendation G.1080, Quality of Experience Requirements for IPTV Ser- vices, December 2008. 7 B. Fenner, M. Handley, H. Holbrook, I. Kouvelas, Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised), RFC 4601, August 2006. 8 ITU-T Recommendation P.800, Methods for Subjective Determination of Transmis- sion Quality, August 1996. 9 ITU-T Recommendation P.800.1, Mean Opinion Score (MOS) Terminology, July 2016. 10 ITU-T Recommendation P.800.2, Mean Opinion Score Interpretation and Reporting, July 2016. 11 ITU-T Recommendation P.10/G.100, Vocabulary for Performance, Quality of Service and Quality of Experience, November 2017. 12 ITU-T Recommendation P.862, Perceptual Ev