In addition to the OpenFlow controllers that we introduced in this chapter, there are also two special-purpose OpenFlow controllers: FlowVisor and RouteFlow. The former acts as a transparent proxy between OpenFlow switches and multiple OpenFlow controllers. It is able to create network slices and can delegate control of each slice to a different OpenFlow controller.

FlowVisor also isolates these slices from each other by enforcing proper policies. RouteFlow, on the other hand, provides virtualized IP routing over OpenFlow-capable hardware. RouteFlow can be considered as a network application on top of OpenFlow controllers. It is composed of an OpenFlow Controller application, an independent server, and a virtual network environment that reproduces the connectivity of a physical infrastructure and runs the IP routing engines.

The routing engines generate the Forwarding Information Base (FIB) into the Linux IP tables according to the configured routing protocols (for example, OSPF and BGP). These special controllers are presented in more detail in the further chapters.