t applications. Class-6 and Class-7 are only provisionally specified in the table. However, such QoS classes are needed for certain new or emerging applications with strict performance parameters. They also introduce in their definition a new parameter named IP packet reordering ratio (IPRR), which has the same upper bound as IPER for these two classes. The specified upper bounds on IP-network performance parameters refer to end-to-end QoS provisioning, which is not an easy task to implement in the existing Internet. On the other side (the users' side), the concept of QoS is attractive if the presentation of services in any type of media (audio, video, data, or multimedia as a combination) at the user interface satisfies the needs and expectations of users. However, such expectations are driven not only by users but also by network providers (which provide broadband access with certain QoS guarantees) and service providers (e.g. OTT service providers which use Internet access service on the basis of the network neutrality). Since QoS is an end-to-end concept by definition, this means that an overall approach is necessary to provide QoS in practice (i.e. end-to-end QoS provisioning). 4 QoS for Fixed Ultra-Broadband 4.5.3 End-to-End QoS Considerations for Network Design Generally, providing end-to-end QoS in IP-based platforms and networks is difficult due to their heterogeneity. Although the telecom world converges on all-IP principles and IP-based networks are using IP protocols on the network protocol layer, that does not mean that all networks and platforms are exactly the same or compatible with each other. This particularly refers to QoS. As discussed in Chapter 1, the Internet is built of interconnected autonomous systems, which are owned by different public and pri- vate organizations (e.g. telecom operators). However, each AS may have different traffic management concepts, which can be completely different from those found in neigh- boring ASs, to which the given AS is connected. More ASs on the path of th