Say each link is of unit bandwidth and each LSP request is also of unit bandwidth. L1 and L2 are two active paths. L1b and L2b can be accomodated on the same link by sharing the bandwidth. Clearly, if either one of L1 or L2 fail the system can recover. Figure 2 illustrates a simple case of sharing of backup paths in a way that single node failure can be recovered.
G are label switch routers.
The intermediate nodes can switchover to the backup path immediately on getting a failure indication. Figure 3 illustrates an example of local restoration for single link failure recovery. Let M be the max of the F values along the active path. The backup path is calculated as follows. All Rights Reserved.