The Floodlight Open SDN Controller is an enterprise-class, Apache-licensed, Java-based OpenFlow Controller. It is supported by a community of developers, including a number of engineers from Big Switch Networks. Floodlight is written in Java and thus runs within a JVM. The source code repository is available on GitHub. The easiest way to get started with Floodlight is to download the Floodlight VM appliance.

In addition to it being an OpenFlow controller, Floodlight is also a collection of applications built on top of the Floodlight Controller. The controller realizes a set of common functionalities to control and inquire an OpenFlow network, while applications on top of the Floodlight controller realize different features to solve different user requirements over the network. The architecture of Floodlight is shown in the following diagram.

The relationship among the Floodlight Controller, the applications built as Java modules compiled with Floodlight, and the network applications built over the Floodlight REST API are shown in the following diagram:

When you start the Floodlight controller, a set of Java module applications, which are loaded in the Floodlight properties file (for example, learning switch, hub, firewall, and static flow entry pusher) start running too. The REST APIs exposed by all running modules are available via the specified REST port (8080 by default). Other Net Apps (for example, the OpenStack quantum plug-in or circuit pusher) can utilize this REST API to retrieve information and invoke services by sending HTTP REST commands to the controller REST port.