te-based model for Internet access, and operators deploy broadband networks to cover demands of the digital society, struggling to return revenues needed to deploy even higher speed networks. Governance and regulations have further limited profitability of operators. In order to increase revenues, operators are deploying a number of service-centric networks on top of the broadband infrastructure such as IPTV, demanding new functionality of carrier network. On the cost side, carrier operators would like to reduce the capital and operational cost significantly. In the following, we discuss the opportunities of leveraging existing cloud technologies for better resource utilization. We will review the related technologies and then outline the rest of this book. Cloud-Enabled 5G: SDN and NFV The Internet has successfully been growing for more than 20 years; the growth in demand has SO far been met by introducing even larger and larger routers. This has been beneficial and to scale in public networks. However, in order to meet today's steadily growing demand for Internet access and other packet-based services, there is a present need to deploy more efficient packet networks also within metro and aggregation network domain. The attempt to copy the approach from the coarsely populated, but large core network sites and migrate to metro and aggregation network sites may not be the most cost optimal approach. It may be time now to split the router architecture in similar ways as was done in the traditional mobile core network, in order to penetrate the highly dense metro/aggregation networks. 1 Introduction Splitting the router control and forwarding plane forms the initial idea of software-defined networking (SDN). The initial idea was born to decouple the routing intelligence software from simple forwarding hardware allowing, particularly for academic research networks and test beds, fast prototyping and eval- uation of new control theories and algorithms [7]. It was part of the Clean Slate Internet Design initiative of S