# Reduced Overhead Routing in Short-Range Low-Power and Lossy Wireless Networks +
## 5 Performance Evaluation
### ERPL's P2P Routing and Data Forwarding Performance Evaluation
#### 5.1.2 Results Using Grid Network Topology  
Here we present the protocol's performance based on a grid network topology. Figure 8 shows EPRL's performance based on a grid topology when the gateway is placed at the center of the network. Figure 7(a) shows the mean PDR demonstrated by the protocols in MP2P, P2 MP, and P2P communications. Compared to standard RPL, EPRL demonstrates higher PDR in all cases. The performance difference among the evaluated protocols increases as we decrease the data packet generation interval. The EPRL P2P forwarding algorithm tries to lowers the number of transmissions required to deliver a P2P data packet to its destination, hence the performance difference between the protocols increases as we decrease the data packet generation interval. EPRL's enhanced P2P routing and forwarding algorithm also positively impacts MP2P and P2 MP communication performance, which is similar to the random network topology results.  
Figure 7(b) shows the mean per-packet end-to-end delay achieved by the protocols with MP2P, P2 MP, and P2P communications. In all cases, EPRL demonstrates lower delay compared to standard RPL. The performance gap between the protocols increases as we decrease the packet generation interval. The reason for this is the same as discussed for the PDR results. With an increase in the packet generation interval both protocols demonstrate lower delay due to lower data traffic load in the network.  
Figure 7(c,d) shows the two protocols' performances with regard to the number of times P2P packets are relayed in the network and the total number of re-transmissions. The number of times P2P packets are relayed in the network using EPRL is lower compared to standard RPL. Moreover, EPRL demonstrates fewer re-transmissions. As EPRL relays P2P packets less, this results in a lower contention, hence ERPL demonstrates better PDR, delay, and total number of re-transmissions in the grid network topology as well.  
Figure 8 shows the performances of the two protocols based on the grid network topology when the gateway is placed at the network's center. Figure 8(a) shows the two protocols' PDR. The trends  
Figure 8: Protocols’ Performances with Grid Topology (Gateway at Network Edge).  
shown in Figure 9a are similar to the trends shown in Figure 8a. Comparison of Figures 8a and 9a reveals that placing the gateway at the center of the network slightly improves MP2P and P2 MP communications' PDR, however the PDR corresponding to P2P communication is negatively impacted. This happens exactly due to the same reason that we discussed above for random network topologies.  
Figure 9b shows the mean per-packet end-to-end delay achieved by the protocols with MP2P, P2 MP, and P2P communications. The trends shown in Figure 9b are similar to the trends shown in Figure 8b. However, MP2P and P2 MP communications experience lower delay compared to the delay experienced by the communications when the gateway was at the edge of the network. This is due to the fact that on average MP2P and P2 MP forwarding paths are shorter when the gateway is at the center of the network.  
Figure 9c,d show the protocols comparison with regard to the number of times P2P packets are relayed in the network and the total number of re-transmissions. The trends shown in Figure 9c,d are similar to the trends shown in Figure 8c,d respectively. Fewer total P2P transmissions associated with ERPL results in the protocol's superior performance overall.