Method for Finding Protected Links to Keep Robust Network Against Link Failure Considering Failure Probability

Abstract

It is important to design and operate a reliable network which is sufficiently robust against network failures. Particularly, in the content distribution service, it is necessary to minimize the probability of service interruption due to disconnection of the communication path between the node receiving the service and the server. For that purpose, it is desirable to protect all links so that the failure probability of a link is almost zero by sufficiently backup resource and rapid recovery system. We can consider such a protected link does not fail. However, link protection needs much cost; therefore, it is important to find the smallest number of links to be protected so that a network resulting from failures of any non-protected links provides the connectivity. In this paper, we take failure probability of links into consideration. In the previous research, it was assumed that the links are protected so that the probability that the whole network does not satisfy the condition of the connectivity is zero. Practically, however, it is sufficient to reduce failure probability of a network sufficiently small. It implies that we can design a practically reliable network with the small number of protected links. First, we formulate this problem and show that this problem is NP-hard. Furthermore, we propose two heuristic algorithms to solve the problem. In addition, we show some examples of application of the heuristic algorithms to the topology of the various actual networks and evaluate the performance of the algorithms.