Abstract: The end-to-end nature of Internet congestion control is an important factor in its scalability and robustness. However, end-to-end congestion control algorithms alone are incapable of preventing the congestion collapse and unfair bandwidth allocations created by applications that are unresponsive to network congestion. To address this flaw, we propose and investigate a novel congestion avoidance mechanism called Network Border Patrol (NBP). NBP relies on the exchange of feedback between routers at the borders of a network in order to detect and restrict unresponsive traffic flows before they enter the network. An enhanced core-stateless fair queueing mechanism is proposed in order to provide fair bandwidth allocations among competing flows. NBP is compliant with the Internet philosophy of pushing complexity toward the edges of the network whenever possible. Simulation results show that NBP effectively eliminates congestion collapse that, when combined with fair queueing, NBP achieves approximately max-min fair bandwidth allocations for competing network flows.