Congestion control for connectionless networks via alternate routing

A congestion control scheme based on alternate routing for connectionless high-speed data networks is presented. In this scheme, if a trunk in the primary path is congested, then a portion of the traffic intended for that trunk is offered to a secondary trunk. The primary path is the shortest distance path in hop count, while the secondary path is at least one hop more than the shortest path. A key innovation is an algorithm for distributed computation of secondary paths which are guaranteed to be loop-free. The secondary trunk accepts the alternate-routed traffic only if it is uncongested. The alternate-routed traffic is given lower loss priority by the trunks along the secondary path so that the primary traffic carried by these trunks does not suffer significant performance degradation. Performance results show that alternate routing affords at least an order-of-magnitude improvement in end-to-end packet blocking under sustained focused overload. The utility of this scheme is demonstrated in the context of IEEE 802.6 networks