Connection Preemption: Issues, Algorithms, and a Simulation Study

Connection preemption can be a means to provide available and reliable services to high-priority connections when a network is heavily loaded and connection request arrival patterns are unknown, or when the network experiences link or node failures. We present a simulation study of preemption in a general connection-oriented network setting. Based on the observations made in this study, we have developed two optimal connection preemption selection algorithms that operate in a decentralized/distributed network where individual link managers run the algorithm for connection preemption selection on their outgoing links. The first algorithm optimizes the criteria of (i) the number of connections to be preempted, (ii) the bandwidth to be preempted, and (iii) the priority of connections to be preempted, in that order, and has polynomial complexity. The second algorithm optimizes the criteria of (i) the bandwidth to be preempted, (ii) the priority of connections to be preempted, and (iii) the number of connections to be preempted, in that order, and has exponential complexity. We conclude that the polynomial algorithm is almost as good as the exponential algorithm in terms of overall network performance.