Efficient Network Modification to Improve QoS Stability at Failures

When a link or node fails, flows are detoured around the failed portion, so the hop count of flows and the link load could change dramatically as a result of the failure. As real-time traffic such as video or voice increases on the Internet, ISPs are required to provide stable quality as well as connectivity at failures. For ISPs, how to effectively improve the stability of these qualities at failures with the minimum investment cost is an important issue, and they need to effectively select a limited number of locations to add link facilities. In this paper, efficient design algorithms to select the locations for adding link facilities are proposed and their effectiveness is evaluated using the actual backbone networks of 36 commercial ISPs.