# Enhanced Multicast Repair Fast Reroute Mechanism for Smart Sensors IoT and Network Infrastructure
## 6 Evaluation of the EM-REP Proposal
### Evaluation of the EM-REP Mechanism  
The main advantage of the M-REP IPFRR mechanism is that the algorithm does not depend on precomputations and even on the unicast routing protocol used. Respecting these properties, we may argue that the M-REP IPFRR mechanism is unique compared to the analyzed ones, as well as other existing IPFRR solutions. The extensions of the M-REP proposed in this paper solve several limitations that have not been resolved in legacy M-REP proposal.  
The enhancement described in Section 5.1 has introduced recovery mechanisms that support fast reroute in the event of multiple and persistent connection and node failures thorough the whole network. In situations when subsequent and recurring errors occur concurrently over time, the EM-REP mechanism encapsulates protected flow into several specific multicast distribution trees, or (S, G) traffic groups. For each multicast distribution group, its router S as the root of the distribution tree encapsulates and floods packets through any of its functional links to all PIM-DM neighbors. Therefore, even if a link or node failure occurs in several places, if there is still at least one possible path from the source S to the destination D, the EM-REP mechanism can find it and use it as an alternative path. This is a unique behavior of EM-REP that provides the 100% repair coverage. This behavior was among other ones simulated by the complex scenario just described. Here we have simulated three consecutive network failures. The simulation results confirmed expected core EM-REP behavior (detection, encapsulation, and flooding), as well as the extended protection against multiple failures, as we proposed in Section 5.1. The EM-REP mechanism has constructed several distribution trees and protects the data of the specified protected flow from multiple failures. The mechanism ensures that all packets of the protected flow were delivered to its destination D.  
The second enhancement, which was described in Section 5.2, addresses the issue that in the original M- REP mechanism, the destination host has to be directly connected to a network with a router that performs decapsulation (router D). The extension also reduces a flooding process of M-REP packets in a network with multiple routing areas.  
Compared to other existing IPFRR mechanisms, the concept of the M-REP mechanism (as well as its enhanced version EM-REP) brings several advantages in addition to the mentioned ones. Some of its drawbacks are also known. An overview of advantages and disadvantages of the EM-REP mechanism is given in the Table 6.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time** & **Source/Destination** & **Name** & **Destination Address** \\ \hline
215.00007242 & \(\rightarrow\)R01 & UDPBasicAppData-185 & 192.168.66.2 \\
215.00008484 & R01 \(\rightarrow\) R02 & UDPBasicAppData-185 & 226.1.1.1 \\
215.00008484 & R01 \(\rightarrow\) R03 & UDPBasicAppData-185 & 226.1.1.1 \\
215.00009726 & R02 \(\rightarrow\) R04 & UDPBasicAppData-185 & 226.1.1.1 \\
215.00009726 & R02 \(\rightarrow\) R23 & UDPBasicAppData-185 & 226.1.1.1 \\
215.00009726 & R03 \(\rightarrow\) R32 & UDPBasicAppData-185 & 226.1.1.1 \\
215.00010968 & R04 \(\rightarrow\) R41 & UDPBasicAppData-185 & 226.1.1.1 \\
215.0001221 & R41 \(\rightarrow\) R42 & UDPBasicAppData-185 & 192.168.66.2 \\
215.00013452 & R42 \(\rightarrow\) H42 & UDPBasicAppData-185 & 192.168.66.2 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The result of the third failure simulation.  
A more accurate comparison of the selected features with other existing IPFRR mechanisms is provided in Table 7 below. As we can see, the EM-REP mechanism is unique in several specific areas.