# Reduced Overhead Routing in Short-Range Low-Power and Lossy Wireless Networks +
## 5 Performance Evaluation
### ERPL's P2P Routing and Data Forwarding Performance Evaluation
#### 5.1.1 Random Topology Results  
We evaluate the protocols using 10 different fully connected random topologies. Moreover, to evaluate the gateway's position impact on the protocols' performances, two different sets of experiments were carried out. For the first set of experiments, the gateway is located at the edge of a network and for the second set of experiments the gateway is located at the center of a network. Figure 6 demonstrates the protocols' performances in random topologies when the gateway is placed at the edge of the network. The mean PDR for the protocols along with 95% confidence interval (CI) around the mean is shown in Figure 5(a). In all sets of experiments, our ERPL protocol demonstrates higher mean PDR compared to the standard RPL-based protocol. For all considered communication types, ERPL demonstrated higher PDR, however the CIs overlap. The protocols' performances change from one topology to another, hence the CIs overlap despite of the fact that ERPL demonstrated higher PDR in each random topology. Generally, as the packet generation interval increases the protocols achieved better PDR due to lower data contention. One of the objectives of ERPL is to focus on improving P2P routing and data forwarding, therefore it outperforms standard RPL by a higher margin in P2P data forwarding compared to the other two types of communication. Figure 5(a) also shows that the improved P2P routing and data forwarding mechanisms of ERPL has a positive impact on MP2P and P2 MP communications. The mean per-packet delay demonstrated by the protocols in P2 MP, MP2P, and P2P communications is shown Figure 5(b). Generally, in comparison to RPL, ERPL demonstrated lower mean per-packet \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline MAC layer & IEEE 802.15.4 CSMA-CA \\ MAC layer ACKs & Enabled \\ \hline Radio model & Unit disk with distance loss \\ Channel rate & 250 kbps \\ MAC layer queue size & 10 frames \\ Node transmission range & 50 m \\ Node carrier sensing range & 100 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cooja Simulation Parameters. Figure 6: Protocols’ Performances with Different Random Topologies (Gateway at Network Edge). end-to-end delay for different communication types. For MP2P, P2P, and P2 MP communications, the CIs corresponding to the protocols overlap despite the fact that ERPL demonstrated lower delay in the different random topologies. This is due to the reason that both protocols' performances differ from topology to topology, hence the CIs overlap. Our improved P2P data packet forwarding algorithm also results in lowering the per-packet end-to-end delay for MP2P and P2 MP communications. The protocols' comparison with regard to the number number of times P2P packets are forwarded in reaching their destination is shown in Figure 5(c). Similarly, Figure 5(d) shows the re-transmission comparison. Using ERPL the number of times P2P packets are relayed in the network is lower compared to the RPL protocol. Furthermore, the number of re-transmissions by ERPL is also lower. As ERPL relays P2P packets less, it demonstrates better PDR, delay, and total number of re-transmissions. The protocols' performances for different random topologies with the gateway placed at the center of the network is shown in Figure 7. The mean PDR achieved by both protocols corresponding to different types of communication is shown in Figure 6(a). Generally, trends present in Figure 6(a) are similar to the trends present in Figure 6(a), i.e., ERPL achieves better PDR in different types of communication, and it significantly outperforms RPL in P2P communication. The comparison of Figures 5(a) and 6(a) sheds light on an interesting insight, i.e., when the gateway is placed at the center of the network, the PDR achieved by the protocols corresponding to MP2P and P2 MP communications is slightly higher and the PDR demonstrated by the protocols corresponding to P2P communication is slightly lower compared to the scenario when the gateway was at the edge of the networks.