# Enhanced Bit Repair IP Fast Reroute Mechanism for Rapid Network Recovery
## 4 The Proposal of the Enhanced B-REP Mechanism
#### The EB-REP State Diagrams
\begin{table}
\begin{tabular}{c c} \hline \hline State: & Router S \\ Event: & Recovery of connection on protected interface OR control signal received OR timer expired. \\ New state: & **Init** \\ \multirow{2}{*}{Action:} & The S router stops the EB-REP encapsulation of the protected flow and changes to the Init state. \\  & In the Init state, it must reinitialize the EB-REP table and EB-REP backup table. \\ \hline \hline State: & Router S \\ Event: & Recovery of connection on protected interface OR \\ \multirow{2}{*}{New state:} & **Init** \\ \multirow{2}{*}{Action:} & The exS router stops the EB-REP encapsulation of the protected flow and changes to the Init state. \\  & In the Init state, it must reinitialize the EB-REP table and EB-REP backup table. \\ \hline \hline State: & Router N \\ Event: & Process received EB-REP packets. \\ \multirow{2}{*}{Action:} & Modify the Bit-String (indicate that packet is processed). \\  & Forward the EB-REP packet to the next-hop according to the Bit-String value. \\ \hline State: & Init \\ Event: & Receiving an EB-REP packet with a BIER header with the last bit set \\ New state: & Router D \\ Action: & A router has received an EB-REP packet. Checks the Bit-String value and detects that values have only the last bit \\  & set, and at the same time, that the bit corresponds to itself. The router becomes the D router. \\ \hline State: & Router D \\ Event: & Process received EB-REP packets. \\ New state: & **-** \\ \multirow{2}{*}{Action:} & Removes a BIER header (which means that packet is decapsulated and returned to its original state). Routes the \\  & original packet via the unicast routing table. \\ \hline State: & Router N, Router D \\ Event: & The timer expires OR control signal received \\ New state: & Init \\ Action: & When EB-REP process is finished, returns to the Init state. In the Init state, it must reinitialize the EB-REP table and \\  & EB-REP backup table. \\ \hline State: & Router N \\ Event: & Detection of EB-REP next-hop failure \\ New state: & Router exS \\ Action: & Looks for a new BS value in EB-REP BT. Replaces the BS value with the new one. \\  & Sends an encapsulated packet through an active interface to the precalculated next-hop EB-REP node. \\ \hline State: & Router exS \\ Event: & Process received EB-REP packets. \\ New state: & **-** \\ \multirow{2}{*}{Action:} & Forwards the EB-REP packet to the new next-hop according to the new Bit-String and the B-REP Backup Table. \\ \hline State: & Router exS \\ Event: & Recovery of connection on protected interface OR \\ \multirow{2}{*}{New state:} & convergence finished OR control signal received OR timer expired. \\ New state: & **Init** \\ \multirow{2}{*}{Action:} & The exS router stops the EB-REP encapsulation of the protected flow and changes to the Init state. \\  & In the Init state, it must reinitialize the EB-REP table and EB-REP backup table. \\ \hline State: & Router exS \\ Event: & Receiving an EB-REP packet with BIER header AND detecting a last bit = 1 in the Bit-String. \\ New state: & D \\ \multirow{2}{*}{Action:} & A BIER header (decapsulation process) is removed from the received packet. \\  & The packet is delivered to the next-hop according to the router D unicast routing table. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._