TDM circuit IP packet Digital video switching switching broadcasting SDH transport IP/MPLS/VPN Broadcast networks transport networks transport networks IMS - IP multimedia subsystem MPLS - Multi-protocol label switching NGN - Next generation network Internet PSTN - Public switched telephone networks network SDH - Synchronous digital hierarchy SS7 - Signaling system no. 7 TDM - Time division multiplexing VPN - Virtual private network Internet services and applications (web, email, etc.) Internet Figure 3.1 Network concept changing from traditional telecom networks to NGN. On the other side, IP hides the network interfaces from the upper protocol layers (e.g. the transport and application layers), thus providing single network abstraction (through the socket interface) to the applications running on the top of the IP stack (even in cases when there are several network interfaces on a given host). So, while the Internet was designed with separated transport and service parts, with IP (including both IPv4 and IPv6) as the main protocol between them in each host and each network node connected to the Internet, NGN puts that into a well-defined framework which specifies the functionalities in given network nodes and end-user hosts. Transport and Service Stratum of NGNs Following the Internet philosophy of separation of services/applications and transport networks, the NGN provides the same for the legacy services (voice, TV) over IP net- works and some emerging services (e.g. IoT services) [1]. This separation is done in 3 QoS in NGN and Future Networks the NGN by definition of two distinct blocks of functionalities (called stratums), which define the basic reference model for NGNs [3]: NGN service stratum: It provides user functions which relate to transfer of service-related data (e.g. signaling and control information related to voice, video, data, and all other services) to network-based service functions which manage service resource and network services with a goal of enabling user applications and services. So, 