Connectivity and Stability at Failures in ISP Backbone Networks

When a link or node failure occurs, flows are detoured around the failed portion, so the hop count of flows could change dramatically as a result of a failure. It is therefore important to evaluate the reliability of backbone networks from the viewpoint of flow hop length stability as well as network connectivity. In this paper, we analyze the possible primary causes of the degradation of reliability of the backbone networks of 36 commercial ISPs and present guidelines for making effective investments in link addition.