e is that it is harder to implement using today's cloud platforms and it is likely to be part of future deployments. It is also important for the 5G network to enable each network function (NF) to directly interact with other network functions. The architec- ture design does not preclude the use of an intermediate function to help route control-plane messages. It is also desirable to minimize dependencies between the access network (AN) and the core network. There are some new concepts that have fundamentally changed the framework of 5G net- works and made them differentiated from the previous generations. 5G network architecture leverages structural separation of hardware and software, as well as the programmability offered by software-defined network (SDN) and network function virtualization (NFV). As such, 5G network architecture is a native SDN/NFV architecture covering mobile/fixed terminals, infrastructure, NFs, enabling new capabilities and management and orchestration (MANO) functions. One of the most innovative concepts that has been incorporated into the design of the next-generation networks is the separation of user-plane and control-plane 5G NR. DOI: https://doi.org/10.1016/B978-0-08-102267-2.00001-4 © 2019 Elsevier Inc. All rights reserved. 2 Chapter 1 functions, which allows individually scalable and flexible centralized or distributed network deployments. This concept forms the basis of the SDN. Other schemes include modularized functional design, which enables flexible and efficient network slicing. Having such require- ments in mind, third-generation partnership project (3GPP) has developed a flat architecture where the control-plane functions are separated from the user plane in order to allow them to scale independently. Another central idea in the design of 5G networks has been to mini- mize dependencies between the AN and the core network with a unified access-agnostic core network and a common AN/core network interface which integrates different 3GPP and non-3GPP access types. In order to f