ate the VNF and release all its resources. VIM controls and manages the NFVI components, to better accommodate the need for various network services. For com- pute resource, it manages the physical resources and the virtual resources, for example, servers, VMs, CPUs, and memories. For networking, it controls the network devices, links, routing, addressing, and QoS. There are various open-source activities on MANO development. SDN controller is considered an integral part of MANO to control the network resources. Besides the three main components, there are other aspects such as fault tolerance, policy management, security and privacy. In the following, we discuss two interesting problems in the NFV orchestration area. 3.4.1 NFV Performance Characterization Before deploying VNF to the production network, the service provider needs to extensively test and validate the VNFs given the high require- ment on availability and performance. However, today there is no way for the service provider to prevent or detect the performance degra- dation caused by third-party VNFs. Similar to other applications, the underlying hardware server characteristics have a deep impact on the performance. Parameters such as processor architecture, clock rate, memory channels and speed, memory latency, and bandwidth of interprocessor buses have a strong impact on the performance of the specific application or VNF running on that HW. In NFV, we need to allocate resources to not only one single server but multiple servers. Scaling to a huge number of devices, connections, and services is indeed a challenge. Every component of the system will need to scale up and scale down with demand variations. This is necessary for efficient operation and obtaining the cost savings required. But, how much resources to give to each VNF? Answering this question is not easy. Different VNFs may have different requirements on compute and network resources. For example, while firewalls are bounded by network throughput others such as load balancer may be bounded