various types of messaging services which have less stringent QoS requirements regarding delay and jitter (on the other hand, they require lossless transmission). Besides service-specific QoS parameters, there are service-independent QoS param- eters which include mobile technology dependent parameters (e.g. for radio access net- work), or general IAS availability parameters (e.g. DHCP or DNS parameters). Service independent QoS parameters [14], include the following: radio network unavailability, network non-accessibility, attach failure ratio, attach set-up time, Packet Data Protocol (PDP) context (in 3G) or Evolved Packet System (EPS) bearer (in 4G) activation failure ratio, PDP context/EPS bearer activation time, PDP context/EPS bearer cut-off ratio, data call access failure ratio, data call access time, DNS host name resolution failure ratio, as well as DNS hostname resolution time [14]. One of the most important service-independent KPIs for data services are referred to DNS availability and DNS response time, which refer to almost all Internet-based services (e.g. Web-based services, email), including mobile and fixed networks. Why? Because the DNS connects the two name spaces in the Internet, IP addresses (IPv4 and IPv6) and domain names. Without proper functioning of the DNS (as well as DHCP because the DHCP sets the IP addresses of the DNS servers at the end-user hosts), even in the case there is available IAS (i.e. through an access network) there would be in practice no access to data services over the IAS, either through fixed or mobile access. Considering the end-user's point of view, there are no differences between mobile broadband access and fixed broadband Internet access (i.e. access to data services). So, the KPIs for data services are those given in Table 7.6. 5G mobile networks have novelties with the use of network virtualization and defini- tion of network slices. KPIs in 5G mobile networks are directly related to the three main 5G network slices: eMBB, URLLC, and mMTC. These also define th