td. 6 Services in Fixed and Mobile Ultra-Broadband in mobile networks. In the 2020s all voice services will in fact be VoIP-based. But regarding QoS, there are two main types of VoIP services: QoS-enabled VoIP services, which are in fact a replacement for legacy digital (or analogue) telephony by telecom operators (including fixed and mobile ones) with VoIP with guaranteed QoS end-to-end (in the same manner as legacy telephony). OTT VoIP services, such as Skype, Viber, WhatsApp, which are provided as OTT ser- vices over network neutral Internet access, without any QoS guarantees, with equal treatment to the other Internet traffic. For QoS provision to voice services in IP-environments the fundamental part is sig- naling. As was practice on a global scale for legacy telephony in the twentieth century, the signaling needs to be standardized globally since the voice services are global (aiming to be vendor independent). How is standardized signaling provided for VoIP in telecom operators' environments? That is accomplished by standardization of NGNs by the ITU [1], which defines end-to-end QoS support for voice by using standardized architectures (by ITU-T) and protocols (by the IETF) [2]. 6.1.1 NGN Provision of VolP Services The NGN was initially developed to provide backward compatibility for operator's voice services over IP networks to PSTN/ISDN [3], and that was accomplished using two main approaches [4]: Emulation approach for operator's VoIP provision. It provides most of the PSTN/ISDN service capabilities by using their adaptation (via emulation) to an all-IP environment in the NGN. Simulation approach for operator's VoIP provision. This refers to the same service provision in the NGN as the emulation approach but without guarantees for all PSTN/ISDN features that were available before the transition to VoIP telephony. NGN QoS-enabled voice provision is used for both mobile and fixed access networks. While in the fixed access network the point of end-user network attachment does not change over time, in mobi