Abstract: In a packet network, on receiving a packet a receiving host determines if the packet has been marked by any of the nodes through which it passed, to indicate congestion at that node, e.g. by checking the CE bit in an IP header. A packet flow control parameter is generated at the receiving side, and sent to the source using an Internet Protocol, as part of the packet acknowledgment, to control the flow of packets from the source, according to the packet flow control parameter. This can reduce control loop delays caused by waiting at the source for a number of acknowledgments to arrive before the congestion level can be calculated. Conditions at the receiver which may be different to those at the source can now be taken into account in the flow control.

Abstract: In a router in a network comprising a source node, and a receiver node, and other nodes, a congestion monitor determines a degree of congestion, which is sent back to the source node, using an OSI network layer protocol. This enables the flow of packets from the source to be controlled more accurately to maintain high throughput with reduced probability of congestion. Using the network layer rather than lower layers can ensure the indication can be carried across the entire network, and not be lost at boundaries between data links making up the network.