mentations, which include legacy (non-SDN and non-NFV) network elements together with SDN- and NFV-enabled network devices. 3 QoS in NGN and Future Networks Generally, future networks are expected to be more complex (with many new services in different verticals) and more efficient (higher utilization of the same network infras- tructure for all services), considering all given awareness aspects. The standardized form of NFV is called network slicing (e.g. network slices are defined in 5G mobile networks). However, there are several other terms associated with the same issue. For example, in the series of recommendations for NGN and future networks, ITU-T has standardized logically isolated network partitions (LINPs), which is in fact network slicing. QoS is important for all networks; however, when a physical network is separated into logical network slices, the QoS may be more important in certain slices (i.e. isolated network partitions) than in others. 3.7.1 Network Virtualization and QoS Network slicing and virtualization were defined as early as the end of the 2000s [24], set as the target for the development of the future Internet, so-called management and service-aware networking architectures (MANA). Among some of the main slicing capabilities are the following: Infrastructure capabilities. These include the introduction of virtualization and programmability in network nodes, such as core nodes, edge nodes (e.g. switches, routers, gateways), as well as wireless and mobile nodes. Control and elastic capabilities. They include (but are not limited to) cognitive control (by decoupling of the user plane and control plane in telecommunication systems), self-configurability of the network components and the networks, as well as flexible and cost-effective operations of different service platforms. Accountability capabilities. They include, for example, cross-layer optimization, including physical resources, the network as a whole, transport and service layers (or stratums) to provide application-enabled QoS ap