ALE: Adaptive link establishment in OSPF wireless ad-hoc networks

Link state routing protocols such as OSPF synchronize the topology databases by flooding link state update messages periodically or whenever there is a connectivity change. When deployed in wireless networks with mobility and noisy channels, OSPF incurs frequent link creation and deletion and subsequent route changes. To cope with this problem, we propose an Adaptive Link Establishment (ALE) scheme that creates a link based on its stability in terms of connectivity and channel condition. The key characteristic of the ALE scheme is that it dynamically controls the latency of a new link creation by either accepting or dropping incoming Hello messages without generating additional control packets on the wireless channel. In addition, the ALE scheme is fully compatible with the legacy OSPF routing protocol. The ALE scheme has been implemented in the real OSPF routing protocol. We measure the performance of the ALE scheme in terms of flooding overhead, convergence time, packet drop rate and throughput. Our experiment results show that the ALE scheme effectively suppresses the unnecessary link establishment caused by intermittent connectivity while having no impact on the convergence time when the network topology is stable. They also show that the end-to-end application throughput is improved by up to 66%.