Patent ID: 6741555
Filing Date: 2004-05-25
Classification: H04L,H04W

Abstract:
A method of avoiding congestion in a network, comprising:transmitting, at a source node, data packets to a destination node, via at least an intermediate node, each data packet including a Transmission Control Protocol (TCP) header; determining, at the intermediate node, if an incipient congestion is encountered, and if the incipient congestion is encountered, setting a Congestion Experienced (CE) flag in each data packet which indicates the incipient congestion to notify the incipient congestion to the destination node; receiving, at the destination node, a CE data packet, setting an Explicit Congestion Notification-Echo (ECN-Echo) flag in the TCP header of an acknowledgment (ACK) packet subsequent to the CE data packet received, and sending an ECN-Echo ACK packet back to the source node to inform that the incipient congestion was encountered in the network on the path from the source node to the destination node; upon receipt of the ECN-Echo ACK packet, reducing, at the source node, a congestion window and a transmission rate to avoid the congestion, and determining if a packet loss is due to congestion or due to a transmission error, when the incipient congestion is still encountered in the network on the path from the source node to the destination node; if the packet loss is due to congestion, re-transmitting, at the source node, only a lost packet to the destination node, via the intermediate node; and if the packet loss is due to the transmission error, re-transmitting, at the source node, the lost packet to the destination node, via the intermediate node, while increasing a round-trip timeout (RTO) but maintaining the same congestion window.