Network Function Virtualization

Chapter 4Software-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 SDN applications targeting important network functions such as load balancing/traffic engineering, quality of service (QoS), and fast failure recovery. The SDN controller programs flow rules in the forwarding tables of SDN-enabled network devices, typically using the OpenFlow protocol. As a basic technology, SDN can enable dynamic control and routing in many network environments. For example, modern enterprise networks use SDN applications to provide QoS to latency-sensitive ...