Decentralized Network Connection Preemption Algorithms

Connection preemption provides 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. Coupled Ž . with the capability to reroute connections preempted due to failure or preemption , connection preemption allows a high quality of service to be provided to network connections and bandwidth to be used more efficiently. The main contributions of this paper are the following. It presents a comprehensive simulation study of preemption in a general connection-oriented network setting. Our simulation study also provides useful insights into connection preemption and network dimensioning problems in order to achieve a desired level of network availability. Based on the observations made in this study, we designed two connection preemption selection algorithms that operate in a decentralizedrdistributed network where individual link managers run the algorithm for connection preemption selection on their outgoing links. The first algorithm Ž . Ž . Ž . 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. The second algorithm optimizes the Ž . Ž . Ž . 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. From a comparison study of these two algorithms we conclude that the polynomial algorithm is almost as good as the exponential algorithm in terms of overall network performance. q 1998 Elsevier Science B.V. All rights reserved.