# A Modular IoT Hardware Platform for Distributed and Secured Extreme Edge Computing
## 4 The Extreme-LT Routing Protocol
### Extreme-LT Experimental Evaluation and Results  
#### 4.2.1 Setup, Test Procedure and End Conditions  
Once the functionality of the platform was verified, a series of tests were performed to trial its behavior under the protocol dynamics, particularly pushing its operation to very extreme boundaries. For these tests, the nodes were deployed in an indoor environment, with the network distribution shown in Figure 11. In this schematic representation of the main lab room (approximately 238 m\({}^{2}\)), the red dot represents the root node, acting as a sink, and the yellow dots represent the sensor nodes, able to both generate messages on their own and relay messages from other nodes. The rectangles represent the working disposition of the lab, just as a reference to show the distribution of the nodes and the different locations used during the deployment and testing process. The setup parameters considered to perform the experimental tests are configured as follows: two packet sizes were used: small packets, with a length equal to 15 B, and large packets, with a length equal to 95 B. These two sizes correspond to those of control and data packets used by the protocol. The message interval for the sender nodes was established at 1 s, 0.5 s and 0.1 s respectively (so very \begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & **Node A** & **Node B** & **Node C** & **Node D** & **Node E** \\ \hline Received & 1087 & 1079 & 1090 & 1094 & 1085 \\ \hline Total & 1103 & 1099 & 1104 & 1103 & 1104 \\ \hline PDR (\%) & 98.606\% & 98.198\% & 98.808\% & 99.203\% & 98.308\% \\ \hline  & **Node F** & **Node G** & **Node H** & **Node I** & **Node J** \\ \hline Received & 1095 & 1069 & 1090 & 1083 & 1089 \\ \hline Total & 1103 & 1103 & 1112 & 1103 & 1107 \\ \hline PDR (\%) & 99.303\% & 96.1012\% & 98.24\% & 98.206\% & 98.414\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Traffic test: saturation of the sink node. aggressive traffic conditions, in which all the nodes are transmitting and routing packets intensively), with 3 different intervals tested over 2 different packet sizes, for a total of 6 test rounds, where each node generates a minimum of 1000 packets per iteration, as shown below. This setup parameters are summarized in Table 6.  
For each round of testing, the sensor nodes were deployed and turned on in the positions shown in Figure 11, then the root node was connected. By connecting the root node last, the route creation will start from the root node and propagate downstream to the rest of the nodes. This is the second network creation mechanism described in the protocol. An example of the network creation procedure for the setup used in the tests is shown in Figure 12. The topology is established by the network depending on the deployment conditions of the moment. After joining the network, each sensor node started sending packets towards the root node, be it directly or through multiple hops, bouncing in the intermediate sensor nodes. The distribution of the nodes in the lab was the same for all the tests, with their positions fixed, and the connections between them were established automatically according to the protocol, thereby creating some differences in the position of each individual node within the topology. Because of these differences, the nodes will not be addressed individually but attending to their rank in the network: the sink node has rank 0, the nodes directly sending to it have rank 1, and so on. Each round of testing was stopped after every node had sent a minimum of 1000 packets to the sink. With this, the PDR of the nodes can be measured and compared, to determine the impact of the packet size and sending interval. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Parameters** & **Round 1** & **Round 2** & **Round 3** & **Round 4** & **Round 5** & **Round 6** \\ \hline Packet size & 15 B & 15 B & 15 B & 95 B & 95 B & 95 B \\ \hline Sending interval & 1 s & 0.5 s & 0.1 s & 1 s & 0.5 s & 0.1 s \\ \hline \hline \end{tabular}
\end{table}