# A Software-Defined Networking Framework to Provide Dynamic QoS Management in IEEE 802.11 Networks
## 4 Evaluation
### SDN-Based Framework Implementation
#### 4.2.2 Simulation Results  
Unlike other tools used in the field of SDN research, such as the well-known Mininet emulator, Estinet 9.0 can be used to evaluate accurately a wide set of properties of the links that connect the OpenFlow network elements. In this work, Estinet 9.0 SDN Wifi-Infrastructure simulation mode offered us the required control over the IEEE 802.11a protocol implementation. Considering the parking slot scenario, multiple situations could be taken into account according to the camera that launches the Alarm. By way of example, this section shows the response of the implemented system when CAM11 generates the Alarm message. The 802.11a data rate is set to 24 Mbps, and the initial value of \(CW_{min}\) is set to 31 (the protocol default value). Figure 7: CDF of the Tail latency. The number of competing stations is set to \(n=10\). Due to the missing of Wifi cameras in the simulator tool, we have used the _lperf_ tool to test the bandwidth performance of the cameras. In the normal transmission mode, each terminal generates an UDP stream at a rate of 0.9 Mbps. The data rate required by the transmission of 4 CIF@12 video streaming is around this value. A 720p@12 fps video streaming requires twice the data rate. In the high-demanding transmission mode, each terminal generates an UDP stream at a rate of 1.8 Mbps. Figure 8 shows the throughput obtained by the Wifi cameras when the proposed DEDCA mechanism is not applied. All the cameras start the transmission, in the normal transmission mode, at second 60. At second 120, CAM11 launches an ALARM, and as a result, CAM11, CAM9 and CAM12 switch to the high-demanding transmission mode that will last for 30 s. It can be seen that these three cameras increase their bandwidth, but the required value is not reached. This increment is due to the fact that, considering the 802.11a data rate of 24 Mbps, there is a remaining bandwidth, but it is not enough to respond to the demand of the requesting stations. Figure 9 shows the results obtained if the proposed DEDCA mechanism is applied. Once the ALARM is sent by CAM11, the SDN-based infrastructure allows the SDN controller to realize that a high-demanding transmission is required. The adequate software module determines the _requesting cameras_, and making use of the scalar G defined in the proposed DEDCA mechanism, is also able to select the _giving cameras_ and to obtain required modifications of the contention window size of these stations. Again, the SDN-based infrastructure allows the controller to inform the stations about their new configuration values. Figure 8: Throughput without using the proposed DEDCA mechanism. CAM11, CAM9 and CAM12 switch to high-demanding transmission mode after CAM11 launches an ALARM. After modifying their \(CW_{min}\) value adequately, the requesting cameras (CAM9, CAM11 and CAM12) are able to reach the demanding bandwidth. On the contrary, as it was expected, the seven furthest cameras (CAM1, CAM2, CAM5, CAM6, CAM8, CAM14 and CAM16) suffer a decrement of the throughput due to the increment of their \(CW_{min}\) value. The remaining six cameras (CAM3, CAM4, CAM7, CAM10, CAM13 and CAM15) are considered _normal terminals_. Consequently, due to the fact that their \(CW_{min}\) value is not modified, their performance is maintained. It can be also observed that the _giving_ cameras actually reach a throughput slightly higher than the expected. The reason is the remaining bandwidth that we could observed in Figure 8. The complete data rate (i.e., 24 Mbps) was not consumed by stations. Now, thanks to the application of the DEDCA mechanism, the _requesting cameras_ obtain the required bandwidth. The _normal cameras_ are not affected and still obtain the adequate throughput. Finally, the _giving terminals_ reduce their throughput, but CSMA/CA distributes the remaining rate among them. Finally, it can be observed that, as usual in shared networks, the throughput oscillates.