Performances of OpenFlow-Based Software- Defined Networks: An overview <s> A. Some Performance Studies <s> This paper presents an independent comprehensive analysis of the efficiency indexes of popular open source SDN/OpenFlow controllers (NOX, POX, Beacon, Floodlight, MuL, Maestro, Ryu). The analysed indexes include performance, scalability, reliability, and security. For testing purposes we developed the new framework called hcprobe. The test bed and the methodology we used are discussed in detail so that everyone could reproduce our experiments. The result of the evaluation show that modern SDN/OpenFlow controllers are not ready to be used in production and have to be improved in order to increase all above mentioned characteristics. <s> BIB001 </s> Performances of OpenFlow-Based Software- Defined Networks: An overview <s> A. Some Performance Studies <s> In the OpenFlow framework, packet forwarding (data plane) and routing decisions (control plane) run on different devices. OpenFlow switches are in charge of packet forwarding, whereas a Controller, which can be situated very far from a networking point of view from the switches its manages, sets up switch forwarding tables on a per-flow basis. The connection between a switch and its Controller is thus of primary importance for the performances of the network. In this paper, we study the impact of the latency between an OpenFlow switch and its Controller. We show that UDP and TCP have different effects depending on the available bandwidth on the control link. Bandwidth arbitrates how many flows the Controller can process, as well as the loss rate if the system is under heavy load, while latency drives the overall behavior of the network, that is the time to reach its full capacity. Finally, we propose solutions to mitigate the phenomenons we outline. <s> BIB002
To evaluate the best controller in term of latency, the authors of BIB001 calculate the latency considered as the average response time with one connected switch and 105 hosts. They show that the smallest latency has been demonstrated by MuL and Maestro controllers, while the largest latency is typical of python-based controllers: POX and Ryu. In BIB002 , the authors consider FloodLight which is a high performing OpenFlow controller that can handle a large amount of flows from a large amount of equipments, and then show that the link between a switch and its controller is of primary importance for the whole performances of the network. In fact, the controller cannot process requests faster than it receives them. In this study, the authors focus on how the controller and the network perform with bandwidth and latency issues on the control link. They adjust the bandwidth with a traffic shaper and the latency by increasing the time a packet has to wait in the egress queue to reach the controller. Increasing the bandwidth leads to a more reactive network due to the controller working at full capacity. Conversely, a low bandwidth will cause some packet losses as the egress queues fill up. The latency has a very different effect on the performances. In particular, the authors show that having a high throughput with a high latency causes bad performances. As each switch has to do a handshake with the controller before being able to send requests, no operation is possible during a time window. For instance, when the latency increases, the time to complete the handshake phase increases until 7s for a latency of 100ms in a 32 switches network. Hence, with a high latency, the packets have to wait longer, thus increasing the probability of packet loss, and it reduces the overall performance of the network. In conclusion, the bandwidth arbitrates how many flows the controller can process, as well as the loss rate if the system is under heavy load, while latency drives the overall behavior of the network.