Congestion detection and clearing history of trip time in AntNet

AntNet-FA showed high potential for best-effort routing through some experiments. However this algorithm was pointed out that it can´t adapt to a situation of traffic change such as congestion. Loop-free constraint is effective for sparse networks, but the constraint has a side effect for scale-free networks. In this paper, we propose an AntNet-based algorithm, AntNet-CHTT (clearing history of trip time). A key point of the algorithm is to determine the case that congestion occurs but it isn´t balanced. And then this congestion is considered not to be transient, the node launches forward ants with loop-free constraint to search other routes for a destination while the congestion continues. Furthermore, the algorithm clears the history of trip time to urge the discovery of other routes, so the algorithm can use network resource effectively. We tested the algorithms on three networks. One of these networks was a sparse network like ring topology and two networks of these networks were a scale-free network.