When the control and data planes are physically separate, it is important to maintain the established connections in the data plane even if the control plane fails. Channel status is maintained by a signalling protocol. A failure in the control plane having no recovery capability of the constraint-based routing label distribution protocol (CR-LDP) will cause the channel status information to be permanently lost. A recovery mechanism for channel status information is proposed in this paper. A downstream node stores a label information database (LID) of assignable (free) labels for each incoming link. A copy of the LID is redundantly stored in the upstream node as a label information mirror (LIM). Each LIM and the corresponding LED are kept synchronised to guarantee the recovery of channel status information. The proposed recovery mechanism is also shown to be applicable to CR-LDP based optical user network interface (O-UNI) signalling protocol.
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