Node Virtualization for IP Level Resilience

For Internet protocol (IP) to evolve into a true carrier-grade transport facility, it needs to support fast resilience out-of-the-box. IP-level failure protection based on the IP fast reroute/loop-free alternates (LFA) specification has become industrial requirement recently. The success of LFA lies in its inherent simplicity, but this comes at the expense of letting certain failure scenarios go unprotected. Realizing full failure coverage with LFA so far has only been possible through completely re-engineering the network around LFA-compliant design patterns. In this paper, we show that attaining high LFA coverage is possible without any alteration to the installed IP infrastructure, by introducing a carefully designed virtual overlay on top of the physical network that provides LFAs to otherwise unprotected routers. Our main contribution is formulating the corresponding resilient IP overlay design problem and providing constructions that can achieve full failure coverage against single link failures by adding at most four virtual nodes to each physical one. We also show that the problem of finding the minimal number of virtual nodes achieving full failure coverage is NP-hard, and thus propose heuristic algorithms that are guaranteed to terminate with a fully protected topology in polynomial time. According to the numerical evaluations the performance of our algorithm is on par with, or even better than, that of previous ones, lending itself as the first practically viable option to build highly resilient IP networks.