Traffic Engineering with MPLS

Tunnel Reoptimization

What happens if, while a tunnel is up, a path appears that is a new best path from head to tail? Consider the network shown in Figure 4-7.

Figure 4-7. New Path Is a More Optimal TE Tunnel Candidate

In Figure 4-7:

• All links start with 100-Mbps reservable bandwidth.

• Router A and Router D both want to build 60-Mbps tunnels to Router H.

• The link between Router D and Router H is down.

Assume that the following sequence of events happens:

• Router D builds a tunnel D→C→H.

• Router A builds a tunnel A→B→C→E→F→G→H.

• Router D reduces its D→C→H bandwidth reservation to 30 Mbps, either by configuration or because of something like auto bandwidth ...