# Enhanced Bit Repair IP Fast Reroute Mechanism for Rapid Network Recovery
## 6 Discussion of the Obtained Results  
The EB-REP FRR mechanism is an advanced version of the older B-REP mechanism. The main advantage of the EB-REP mechanism and an improvement over its predecessor B-REP is the support of protection against multiple failures and per-prefix-based calculation of alternative FRR backup paths. By supporting multiple-network failure protection, the EB-REP mechanism is more robust and flexible in situations of unexpected network error conditions. During the performed simulations, EB-REP was able to find correctly applied precalculated alternative routes, even in the case of multiple outages, and deliver all flow packets to the destination. Simulation results show that our IP FRR mechanism is both practical and feasible and can successfully provide network protection against multiple link or node failures in terms of agility, robustness, and efficiency.  
Per-prefix backup path calculations are a feature that allows the algorithm to calculate the optimal backup path for all destinations and all device output interfaces. All its features make it a unique algorithm in its class of FRR mechanisms. However, as a member of the proactive category of FRR mechanisms, it also inherits some of their disadvantages, namely the need for preliminary calculations and increased consumption of system resources in the form of CPU and RAM, as well as network capacity, caused using tunneling. The main advantages and disadvantages are summarized in Table 12.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Time** & **Source/Destination** & **Name** & **Destination Address** \\ \hline  
(\rightarrow\) H3 & UDPBasicAppData-185 & 192.168.3.2 \\ \hline
80.00008729 & \(\rightarrow\)R1 & UDPBasicAppData-185 & 192.168.3.2 \\
80.00009971 & R1 \(\rightarrow\) R5 & EB-REP-Data & 192.168.3.2 \\
80.00011213 & R5 \(\rightarrow\) R9 & EB-REP-Data & 192.168.3.2 \\
80.00012455 & R9 \(\rightarrow\) R14 & EB-REP-Data & 192.168.3.2 \\
80.00013697 & R14 \(\rightarrow\) R15 & EB-REP-Data & 192.168.3.2 \\
80.00014939 & R15 \(\rightarrow\) R16 & EB-REP-Data & 192.168.3.2 \\
80.00016181 & R16 \(\rightarrow\) H3 & UDPBasicAppData-185 & 192.168.3.2 \\ \hline \hline \end{tabular}
\end{table}
Table 11: Output from the OMNeT++ simulation.  
As with the original B-REP mechanism, the EB-REP mechanism also provides 100% repair coverage, which means the possibility to repair all link or node failures in the network for all possible destinations. We are aware that the computational costs for determining the correct paths for the individual destination addresses may be higher. EB-REP therefore allows the customization of its activity to define a list of protected interfaces or a list of critical prefixes for which the FRR service will be provided. The ability of EB-REP to define the FRR backup path manually, even if the metrics of links are inappropriate or unspecified, can be understood as an advantage to this functionality.  
Like most existing IP Fast Reroute solutions, the EB-REP uses a precomputation system to calculate multi-hop backup paths in advance. For this purpose, the EB-REP uses link-state topology information collected by a link-state routing protocol. Our solution does not depend on the type of link-state protocol used, but for this paper and simulations, we used OSPF v2. A more comprehensive summary of the analyzed features of existing FRR solutions is provided in Table 13.