fferent trade-offs between performance and server usage. Solution procedure: We solve the MIP multiple times for different values of B in the range [0, 1] to produce a set of solutions along the efficient frontier of maximum node utilization versus number of servers. As B increases, the solutions favor decreasing the maxi- mum utilization P over minimizing the number of nodes used. The 3.7 Summary heuristic solution is used as a starting solution for the first MIP, which helps speed its execution. Then, for each new value of B, the preceding solution can be used as a starting point. 3.7 Summary In this chapter, we introduce the NFV overview. We first present the NFV architecture proposed by ETSI and its relationship with cloud computing. We then present its use cases in telecom network. We dis- cuss the challenges in virtualizing the NFs and using them in telecom network. Finally, we further explain the difficulties and problems in deploying NFV in reality, in terms of measurement, characterization, and modeling. Software-Defined Networks Principles and Applications Software-defined networking (SDN) is growing as a solution in dynamic environments where customers need to adapt to new protocols and standards. Different protocols such as OpenFlow have arisen in order to facilitate the implementation and deployment of SDN-enabled networks. Customers are looking for a programmable interface where they can program Ethernet chips to meet their custom needs; with hard-coded silicon and protocol-dependent interfaces, the adaption of new protocols requires several years to develop, implement, test, and deploy. However, customers are also looking to insert SDN vertically in the data path, allowing the SDN application to coexist and function together in addition to traditional forwarding, also facilitate adoption, or solve specific networking challenges. SDN enables centralized, programmatic, and fine-grained control of network flows, based on a global view of the network state. A logically centralized SDN controller runs S