Software Defined Networks (SDN) is a concept that separates the control plane from data plane in network devices. The control plane moves to a central controller. The purpose of the controller is to communicate and dictate how the network devices should forward the traffic. One of the protocols that controllers use to communicate with the network devices is OpenFlow.

The purpose of the thesis is to examine how different SDN-controllers utilize links in a full-mesh topology, how they handle broadcast traffic and the problem with loops. The advantage of a full-mesh topology is that network devices are able to reach each other with just one hop and provides maximum protection against failing devices and links. A problem with redundant links is the risk of broadcast storms and loops.

The controllers have been exposed to four different scenarios. How they handle broadcast traffic and how they use redundant links to forward traffic. If they are enable to load balance and redirect active flows if the link fails.

The controllers used in the tests are: Floodlight, POX and OpenDaylight. They were connected to a virtual network generated by the network emulator Mininet.

Floodlight and POX both utilized the links in full-mesh topology better than STP would in a traditional network. No links were blocked from forwarding traffic without any broadcast storms happening. OpenDaylight were unable to handle our full-mesh topology which led to a broadcast storm. Floodlight and POX couldn’t redirect active flows when the link went down