LDP failure detection and recovery

In the last few years, multiprotocol label switching has been successfully, deployed by the majority of service providers worldwide. The label distribution protocol is used in many MPLS networks for distributing labels to establish the label switched paths. This article focuses on LDP failures, namely failures that may occur in LDP while the underlining interior gateway protocol of choice, and the physical connections are operating normally. Since LDP and MPLS in general do not have intrinsic means for detecting these failures, new mechanisms have to be introduced to handle them. Furthermore, the IGP may remain unaware of the LDP failure, and continue to direct traffic to the faulty path. To resolve this situation, coupling between LDP and the routing protocol may have to be introduced. In this article, we discuss all aspects related to handling LDP failures: discovery, location, notification, recovery, and prevention.