# Software Defined Wireless Mesh Network Flat Distribution Control Plane
## 7 Evaluation
### Control Plane Adaptation  
This scenario shows how FD-SDWMN's controllers exchange control information and control self-adaptation to the network states. To mitigate any congestion in the control messages, exchange links between controllers' agents offload traffic of a weak direct control connection (via a dedicated control channel (out-of-band)), by identifying alternative routes or reducing the control messages frequency on it if no alternative route. For instance, the monitoring agents usually send information every 3 s, and this period changes to 10 s in weak links. Also, connectivity and reachability agents can send their information via alternative routes. However, they are event-driven agents contrary to the monitoring agent.  
Upon control plane bootstrapping and controller discovery, the C1 and C2 are connected to C3 as depicted in Figure 7. In this scenario, the control-link between C1 and C2 is congested (its latency = 50 ms). Thus, the monitoring agent is relaying control messages between C1 and C2 via C3 to offload the congested link.  
Figure 8 presents the conducted evaluation to show FD-SDWMN control plane adaptation with network conditions, e.g., the C2+C3 link failure. The figures show the utilization of the link in both directions, left after C3 discovers C1 and C2 and the AMQP system starts exchanging messages between them. The TCP payload of received packets splits into three stages:  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Software** & **Purpose** & **Version** \\ \hline Ubuntu Linux & Hosting OS & 16.04 \\ Mininet-wifi & SDWN Emulator & 2.2.1d1 \\ POX & SDN Controller & Dart branch \\ FlowVisor [29] & Network slicing & 1.2.0 \\ Open vSwitch & SDN Virtual Switch & 2.0.2 \\ Python & Programming Language & 2.7 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Software used in experiment.  
Figure 7: The control plane adaptation: (**Left**) the congested situation: C1 and C3 use the forwarding link via C2; (**Right**) link disruption: C1 and C3 use the congested control link with adapting information exchange frequency.  
* Local controller discovery: takes the first 9 s where controllers exchange their capabilities to advertise themselves. The AMPQ communication system is active during this period because the brokers should establish the control channel and subscribe to available topics. During this stage, the monitoring process has already started but not adapted to the weak link yet.
* Monitoring adaptation: after the end of the previous stage until t = 33 s. In this period the weak link is discovered by monitoring agents and they start adaptation behavior. As observed in Figure 8a,d, the monitoring stopped from t = 10 s because the C1\(\leftrightarrow\)C3 is congested (weak), at the time in Figure 8b,e, the monitoring traffic is increased over the C1\(\leftrightarrow\)C2 and C2\(\leftrightarrow\)C3 links as in Figure 8b,c,e,f.
* Failure recovery: starts right after the alternative link C2\(\leftrightarrow\)C3 is cut at t = 33. Thus, the monitoring information is forwarded via the congested link C1\(\leftrightarrow\)C3 but in adapted frequency, as in Figure 8b.