A Review of Constraint-Based Routing Algorithms

Constraint-based routing is an invaluable part of a full-ßedged Quality of Service (QoS) architecture. Unfortunately, routing with multiple additive constraints is known to be a NP-complete problem. Hence, accurate constraint-based routing algorithms with a fast running time are scarce, perhaps even non-existent. The expected impact of such a constrained-based routing algorithm has resulted in the proposal of numerous heuristics and a few exact QoS algorithms. Although at times an overview of QoS algorithms has been published, a comparative study to the performance of QoS algorithms is still missing. With this paper we attempt to Þll this gap. This paper aims to give a thorough, concise and fair evaluation of the most important constraintbased routing algorithms known today. We will provide a descriptive overview of restricted shortest path algorithms and multi-constrained path algorithms. A performance evaluation of these two classes of algorithms is presented based on complexity analysis and simulation results.