etects the failure and immediately activates the binding to direct traffic to E. Nodes E, F, and C already have their forwarding rules in place and need not be touched to implement the restoration. All of this happens in 50 ms or less. We call this process fast reroute (FRR). It is fast because it is localized, preconfigured, and only requires that we detect the failure and flip a single bit in B to use the backup tunnel. The term "point of local repair" is used to describe the function performed by B. It is responding to repair the loss of link BC by replacing it with a backup tunnel. But note that the route the end-to- end tunnel from A to D is taking is not optimal. Knowledge of the failure of the link BC was flooded through the network via the routing proto- col. All head-end nodes with tunnels traversing this link began to compute new best paths exclud- ing link BC from their routing database. In our case, node A found the new tunnel path along Common resources could mean the different wavelengths have been multiplexed onto the same fiber, or that they ride different fiber but in the same bundle, or that they are in different bundles but share the same conduit. The optical interfaces on the router can detect when the incoming optical signal becomes SO faint that we cannot decode the information on it or when the bit error rate exceeds a configured threshold. This condition gets reported to the control- ler on the router and would be the trigger to initiate FRR. It would also be reported to management systems to take action to troubleshoot and repair the underlying problem. Building the Network of the Future A-G-H-D. It sends an RSVP signaling message to reserve and assign resources to create this tunnel. Once it gets confirmation back from the nodes along the path, it moves traffic destined for D off the temporary path that uses the backup tunnel, onto the new tunnel. This action is completely hitless-it happens with zero packet loss. The head-end node confirms that the data plane of the new end-to-end tunne