MPLS-Enabled Applications: Emerging Developments and New Technologies

3.11. IP AND LDP FRR

Fast failure recovery is a fundamental requirement for carrying sensitive traffic such as voice or video and is an important building block for providing QoS in MPLS networks. The problem is that the local protection schemes described so far only work in conjunction with RSVP, but many MPLS deployments use LDP as the label distribution protocol.

If an LDP network is to carry voice or video traffic, it must ensure fast failure recovery. Let us see the options available:

• Move away from LDP and switch to RSVP. This is an unacceptable proposition for most providers because it requires a massive reengi-neering of the network.

• Use one-hop RSVP LSPs with link protection to protect selected links, and continue to run targeted LDP sessions over these RSVP tunnels, as shown in Figure 3.22. Note that both under normal conditions and following a failure, LDP traffic is tunneled inside RSVP. When the link fails, traffic on the one-hop RSVP tunnels is protected, so the LDP traffic is also protected. This approach is attractive because it allows the operator to continue to use LDP for the setup of LSPs and does not require changes to the edge routers. However, protection for only link failures can be achieved.

• Find a mechanism that will provide fast-reroute behavior for LDP. This is the most attractive proposition for the customers, and for this reason vendors are actively trying to engineer such a solution. Because this work is still in progress at the time of this writing, ...