Optimizing IGP Link Costs for Improving IP-level Resilience
Recently, major vendors have introduced new router platforms to the market that support fast IP-level failure protection out of the box. The implementations are based on the IP Fast ReRoute-Loop Free Alternates (LFA) standard. LFA is simple, unobtrusive, and easily deployable. This simplicity, however, comes at a severe price, in that LFA usually cannot protect all possible failure scenarios. In this paper, the authors give new graph theoretical tools for analyzing LFA failure case coverage and they seek ways for improvement.