5G technologies are a new paradigm strongly supported by the European Commission (EC) to overcome the challenges of next generation networks and aiming to tackle the novel and manifold business requirements of vertical sectors such as Industry 4.0, Smart Grids, Smart Cities, and eHealth. Extraordinarily high speeds and capacity, multi-tenancy, fixed and wireless access network convergence, self-X, unconventional resource virtualisation, on-demand service-oriented resource allocation and automated management of resources are only few examples of the complex demands that 5G aims to undertake. The accommodation of such features requires multipronged efforts in different network technology domains at various levels. In this paper, we investigate how the relative 5G network features challenge the current generation of access networks, both fixed and wireless, and data centres, from an end-to-end network service point of view. Furthermore, we provide some insights into how emerging technologies such as Network Function Virtualisation (NFV) and Software Defined Networks (SDN) can be utilized for the accommodation of the above mentioned features and realization of 5G networks. 1. INTRODUCTION The 5G promise of a complete networked society with unlimited access to information about anything for anyone demands key features beyond what the current 4G offers. Some of these features include support for new type of large number of devices, for very high mobile traffic volumes, integration of heterogeneous access technologies, ubiquitous access for users, much higher frequency reuse in wireless technologies, end-to-end network security, automated provisioning, configuration and management of a wide range of new network services, extreme reliability, ultra-low latency and high volume DC interconnects, etc. . To deliver a viable solution meeting all 5G requirements, a substantial change on the network paradigm is inevitable. One of the main pillars of such revolution is the way that new network functions are entered to the value chain. Traditionally, such a process demands deployment of specialized devices with 'hard-wired' functionalities. It implies that any adaptation to the ever increasing and heterogeneous market requirements demands a huge investment to change/deploy hardware. Thanks to the advent of cloud computing, Software Defined Networking (SDN) and Network Function Virtualisation (NFV), the idea of having general-purpose computing and storage assets at networks has been realized along with the virtualization of networks and network functions which enables the automation of network service provisioning and management. Given the virtualization of networks and network functions, the 5G features of multi-tenancy and end-to-end security becomes even more challenging. In terms of multi-tenancy, the challenge remain how the isolation among different tenants, utilizing virtual networks on top of possibly the same physical infrastructure, can be ensured at all levels. For ensuring end-to-end security in 5G networks, a holistic approach is required which takes into account not only the physical but also the virtual resources of the network. These challenges require a substantial change on the network devices, from being only network equipment to cloud-enabled devices enhanced with, e.g., novel processor architectures. Besides, a fundamental change on the data centre (DC) infrastructures is essential to meet the needs of future Internet and 5G application. On the IT part of DCs, the number of virtual machines (VMs) created by different server virtualisation technologies has been increasing, and it will double over the next few years . Therefore, it is critical to have an intelligent DC management system to better utilize available resources to accommodate instantiated VMs. Moreover, DC networks with the traditional tree-like architectures are reaching their limits and cannot efficiently cope with the requirements of emerging 5G applications in terms of latency and energy efficiency. This pose a serious challenge on the DC operators to revisit the networks architecture and develop appropriate technologies with low power consumption, low latency and high level of flexibility, at relatively low costs. In this paper, among all abovementioned 5G requirements, we will focus on how an end-to-end security and multi-tenancy solution can be envisioned for 5G networks as well as future DC networks in line with the 5G needs.