Restoration measurements on an IP/MPLS backbone: The effect of Fast Reroute on link failure

In this paper we show data plane restoration measurements for restoration under backbone link failures for a large network with IP/MPLS OSPF routing and also for the same backbone with Traffic Engineering (TE) and Fast Reroute (FRR) deployed. Our study is unique as we analyzed a significant quantity of measurements obtained from a production network over a 14-month period encompassing many link failures. The results show that TE/FRR restoration reduces outage-induced loss-duration substantially as compared to OSPF restoration. We also note that for both OSPF and FRR the course of restoration is not as simple as is commonly believed. A detailed study of the data shows that while loss-duration and overall duration is much reduced, TE/FRR results in path changes with no detectable loss over a period of seconds. Thus implementation of TE/FRR in a network results in a vast improvement in behavior for all data flows.