LDP Extension for FRR Edge Node Protection in BGP-Free LDP Core
draft-bashandy-mpls-ldp-bgp-frr-00

Abstract

Consider a BGP free core scenario with LDP running in the core. Suppose the edge BGP speakers PE1 and PE2 know about a prefix P/m via the external routers CE1 and CE2. If the edge LSR PE1 crashes or becomes totally disconnected from the core, it is desirable for a core LSR "P", that is carrying traffic to the failed edge LSR PE1, to immediately restore traffic by re-routing packets destined to the prefix P/m from the LSP terminating on PE1 to be forwarded over the LSP terminating on PE2, until BGP reconverges. If the packets originally flowing to the failed edge LSR PE1 are BGP labeled, then the repairing core LSR P must swap the label (corresponding to prefix P/m) advertised by the failed edge LSR PE1 with the label advertised for the same prefix by the edge LSR PE2 before re-routing the packets through an LSP terminating on PE2. To implement BGP edge node protection in a BGP-free LDP core, this document proposes an extension to LDP. This extension allows an LDP speaker running on a Edge LSR Node (e.g. PE1) to inform the LDP speakers running on core LSRs about the "Repair" edge LSR (e.g. PE2), as well as Repair LSR's label for prefix P/m, if any.

Authors

Ahmed Bashandy
Syed Kamran Raza

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