LFA Next Hop Computation Relaxing Reverse Cost Metrics
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Solution Overview
Problem
Current Interior Gateway Protocol (IGP) Loop Free Alternative (LFA) computation methods, as defined in RFC 5286, exclude links with maximum reverse cost metrics, leading to situations where potential alternative paths are not considered, thereby limiting network coverage.
Innovation Solution
A method that calculates LFA next hops by selecting candidate next hops, checking for administratively allowable links with maximum forward costs and bi-directionality, and computing LFAs without considering reverse costs, thereby relaxing the link reverse cost requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RFC 5286 criteria are strictly followed to ensure loop-free alternative paths, then network reliability is improved, but network coverage deteriorates due to exclusion of links with maximum reverse cost metrics
Solution Approach 1:
The patent changes the parameter evaluation criteria by removing the reverse cost metric check from the LFA computation process. Instead of evaluating both forward and reverse costs as required by RFC 5286, the invention only evaluates forward costs, thereby including links with maximum reverse cost metrics in the candidate set and expanding network coverage while maintaining loop-free properties through forward cost evaluation
2Device complexity
If links with maximum reverse cost metrics are excluded from LFA computation, then computation complexity is reduced, but alternative path identification capability deteriorates
Solution Approach 1:
The patent extracts and removes the reverse cost metric evaluation step from the LFA computation process. By taking out this specific evaluation criterion while retaining forward cost evaluation and loop-free verification, the invention simplifies the computation process and reduces complexity while simultaneously expanding the set of identifiable alternative paths by including previously excluded links
Data Source
AI summary
A method and implementing system calculates a loop free alternative (LFA) next hop as a backup for a primary path next hop for an interior gateway protocol (IGP). The method enables consideration of the LFA next hop where a link to the next hop has a reverse cost that has a maximum value. The method includes selecting a next candidate next hop from a set of candidate next hops in the network, checking whether a link to the next candidate next hop is an administratively allowable link, and checking whether the link has a maximum forward cost. The method further checks whether the link is bi-directional and computes the LFA using the next candidate next hop where the link is administratively allowable link, where the link does not have a maximum forward cost and where the link is bi-directional without consideration of reverse cost of the link.