SDN solutions are necessary as they allow businesses to simplify their network operations, and it also allows them to automate network functions. It fits well with the DevOps initiative and the need to make network operations more agile.
A byproduct of SDN is that it allows network functions to become as accurate and repeatable as creating a new virtual machine on a hypervisor.
SDN solutions from vendors are made up of a centralized controller that is implemented to become the nerve center of the network. SDN controllers rely heavily on Open vSwitch database (OVSDB), which is a programmable, open standard schema which utilizes the OpenFlow protocol, which integrates directly with switches to route packets in the network as well as applying ACL policies to particular virtual machines, physical servers, or containers.