Controlling a software-defined network via distributed controllers
Distributed Open Flow controller is a result of the EU-funded 'Connectivity brokerage for collaborative optimization of heterogeneous wireless networks' (CONN-BRO) project. Leveraging on the software-defined networking (SDN) paradigm, this cluster-based controller serves as a network operating system. In an SDN network, flows are routed according to rules installed at the switches by controllers. When a flow does not match any of the existing rules, it is redirected to the controller, which comes up with a routing decision. Therefore any malfunctioning or inaccessible controller can put the entire network into an unusable state, and a certain level of reliability and scalability is necessary. This work enabled a distributed controller to address these requirements. The architecture realized the controller as a cluster of machines. Each controller took the responsibility of a certain part of the network. Necessary intra-network information was disseminated for controllers performing inter-network routing. Scalability was provided by sharing switches among multiple controllers. Dynamic addition and removal of controllers from the cluster was provided for reliability. A new controller can be added to the network without taking the entire network down. In case of a controller failure, the rest of the system keeps working and those switches connected to the failed controller migrate to live controllers. The Open Flow protocol, standardised by Open Networking Foundation (ONF), established a common interface for messaging between the controller and virtual or physical switches. OpenFlow is the de-facto SDN protocol in the market and is widely adopted. The project’s distributed controller leveraged Open Flow protocol to realize the aforementioned features. More information on the distributed controller can be found online. The performance of the CONN-BRO architecture was demonstrated on an experimental test bed including desktop PCs, laptops and wireless access points. CONN-BRO research has resulted in a series of publications in renowned scientific journals and submission of additional papers is planned. The outcomes will help Europe take a leading role in the areas of SDN and wireless communications.
Keywords
Software-defined networking, OpenFlow, Distributed Controller, Reliability, Scalability
