IS-IS Extension for BGP FRR Protection against Edge Node Failure
Cisco Systems
Consider a BGP free core scenario where traffic is tunneled between edge routers. Suppose the edge BGP speakers PE1, PE2,..., PEn know about a prefix P/m via the external routers CE1, CE2,..., CEm. If the edge router PEi crashes or becomes totally disconnected from the core, it desirable for a core router "P" that is carrying traffic to the failed edge router PEi to immediately restore traffic by re- routing packets originally tunneled to PEi and destined to the prefix P/m to one of the other edge routers that advertised P/m, say PEj, until BGP re-converges. If the packets originally flowing to the failed edge router PEi are labeled, then the repairing core router P router may need to swap, push, or pop the label advertised by the failed edge router PEi with another label before re-routing the packet through an LSP terminating PEj so that PEj can correctly forward the packet. The document proposes an extension to IS-IS protocol to inform core routers about the repair edge router PEj and, for labeled packets, the label that needs to be pushed/swapped before sending the packet into the tunnel terminating on PEj