Area Border Node FRR Protection for Inter-Area LSP

For protection of the area border router, the upstream node of the area border router acts as a point-of-local-repair (PLR), and the next-hop node to the protected domain border router is the merge-point (MP). Both manual and dynamic bypass are available to protect area border node.

Manual bypass protection works only when a correct completely strict path is provisioned that avoids the area border node.

Dynamic bypass protection provides for the automatic computation, signaling, and association with the primary path of an inter-area P2P LSP to provide ABR node protection. Figure 1 illustrates the role of each node in the ABR node protection using a dynamic bypass LSP.

Figure 1. ABR Node Protection Using Dynamic Bypass LSP

In order for a PLR node within the local area of the ingress LER to provide ABR node protection, it must dynamically signal a bypass LSP and associate it with the primary path of the inter-area LSP using the following new procedures:

Note that a one-to-one detour backup LSP cannot be used at the PLR for the protection of the ABR node. As a result, a PLR node does not signal a one-to-one detour LSP for ABR protection. In addition, an ABR node rejects a Path message, received from a third party implementation, with a detour object and with the ERO having the next-hop loose. This is performed regardless if the cspf-on-loose-hop option is enabled or not on the node. In other words, the router as a transit ABR for the detour path rejects the signaling of an inter-area detour backup LSP.