s (for Ethernet versions which support it) is shown in Table 2.4 [39]. The basic network model (as given in the previous subsection) should be applied com- monly to the providers, but the detailed QoS technologies to compose such a network model would be different for different providers and countries. Additionally, there are differences in the regulation environment, which is a fundamental framework for pro- vision of QoS and QoE. Table 2.4 Mapping between DiffServ, MPLS, and Ethernet. Layer 3 packet Packet marking: DSCP Layer 2 packet marking network (DiffServ code MPLS (class Ethernet (priority QoS class Description point) of service) code point) Applications Classes 0, 1 Jitter sensitive EF (expedited 5 (default) or 6 Telephony forward) Classes 2, 3, 4 Low latency AF (assured 4, 3 or 2 4, 3 or 2 Signaling, forward) interactive data Class 5 Best efforts DF (default Web browsing, forward) email 2.12 Discussion 2.12 Discussion Internet QoS was a very important topic in the 1990s when the two main IETF stan- dards on QoS were developed, IntServ and DiffServ. They are not widely deployed today exactly as standardized, yet their concepts are still alive. Internet capacity exploded in the 2000s with the spread of broadband access networks to residential users, via either fixed access (e.g. X digital subscriber line [xDSL] technolo- gies over twisted pair copper lines, cable access, or fiber access) or mobile access (e.g. 3G, 4G, 5G mobile access networks). When there is a lot of capacity (although one should note that "a lot" is a relative term which refers only to a given point in time), packets are dropped only when capacity is reached. Then, QoS solutions can be very useful when capacity is saturated. With the expansion of the Internet in the 2000s, a huge number of fiber links have been deployed, which give a lot of network capacity. Then, when there is lots of spare capacity, there is less requirement for Internet QoS end-to-end. However, carrier-grade VoIP and IPTV, as well as VPNs as a replacement for leased 