Route flap damping with assured reachability

Abstract

It is well known that a relatively small percentage of unstable routes exists in the global routing system which contributes an out of proportion number of routing updates. The route flap damping (RFD) was once considered an effective means to curtail such instability. However, both measurement studies and operational observations show that BGP path exploration can trigger false route damping which leads to prolonged periods of lost network reachability. As a result, many networks turned off RFD. In this paper we propose a simple solution, RFD+RG, dubbed RFD with Reachability Guard, to address the reachability problem in the RFD deployment. RFD+RG performs route flap damping without losing reachability, and the +RG enhancement component works independently from specific damping algorithms and can be integrated into any existing RFD scheme. We use collected BGP data to evaluate RFD+RG performance and our results show that RFD+RG can suppress up to 27% of route instabilities while faithfully preserving reachability.