US Patent 8009568 Congestion control in stateless domains

Reducing congestion in an IP domain wherein congested data flows arriving at an egress edge node of the network are identified. Total congestion represented by the congested flows is determined, and a congestion extent notification is sent from the egress edge node to its ingress edge node peer. The congestion extent notification includes information regarding the total congestion and is sent on a per-class basis. Congested core routers in the network insert DSCPs into data packets passing through them to enable the egress edge nodes to identify the affected flows. The core routers may also send congestion metric messages, designed to follow the same path as the marked packets, to inform the egress edge nodes of the extent of congestion. In an alternative method, the egress edge nodes inform their ingress peers that congestion is present, without initially identifying the extent. The ingress edge node sends a query downstream with a congestion metric.