Improving the reliability of the label distribution protocol

The LDP (label distribution protocol) is used in the control plane to control an optical network. The data plane and the control plane of an optical network could be physically separate. So a failure in the control plane does not necessarily imply a data plane failure and that user communications have to be interrupted. The standard LDP, however, does not provide any mechanism to recover the knowledge stored in LDP entities about the status of the data plane after the faults are fixed. This is a reliability problem of LDP and results in the unnecessary degradation of user communications. On the other hand, in MPLS-enabled IP networks, being able to recover LDP sessions would be potentially faster and more scalable than to re-establish all affected LSPs. The proposed recovery method of LDP for the control plane failures uses label information mirrors (LIMs) in upstream downstream label switching routers (LSRs). Each LIM is a copy of the label information database (LID) in the LSR of an LDP session. We propose a systematic approach to synchronize the contents of a LIM and the corresponding LID, and show how a LIM is used to handle a control plane failure. Detailed descriptions of the recovery procedure for both control channel failures and control node failures are presented. Some significant features of the proposal are outlined.