rvices to VoIP and the tran- sition of television toward IPTV (although this lags behind VoIP because TV requires far more bits per second to be transmitted with desired QoS). Besides legacy telecommuni- cation services, the twenty-first century provides a plethora of new services enabled by IP networks and Internet technologies, which has paved the way for deployment of new services without a need for change of the underlying network infrastructure. However, some services are provided with QoS support, while others (e.g. Internet-based services) are provided in a best-effort manner. With the deployment of ultra-broadband access, the difference between the two types of services (with and without QoS guarantees) becomes smaller, especially when broadband speeds are sustainable between end-users and other end-peers (e.g. servers) with which users communicate (also, the user can be a human or a machine on both ends, which depends upon the service type). 6.1 QoS-enabled VolP Services By definition, VoIP refers to provision of voice communication service (i.e. legacy telephony as a conversational type of service between two or more humans as the end-users) in both directions (between the end-users) over all-IP networks by using Internet technologies end-to-end. With the transition of all telecommunication networks to IP networks, all services have become IP-based, implemented in the application space. So, all telephony becomes VoIP, including fixed and mobile access. In the case of fixed access networks, there can be analogue voice in the last meters in cases where legacy analogue telephone devices are used (as dumb devices, without any software implemented regarding voice service), connected via twisted-pair copper wires on the user's side. So, every telephony service becomes VoIP, a transition that started in fixed networks in the early 2010s and then continued in the late 2010s QoS for Fixed and Mobile Ultra-Broadband, First Edition. Toni Janevski. © 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons L