Tag :: ECN

Explicit Congestion Notification (ECN) is an extension to the Internet Protocol and to the Transmission Control

This feature introduces a new CLI command which disables the above-mentioned propagation of DSCP and ECN bits from the outer IP header. 

By default, the DSCP and ECN bits of VXLAN bridged packets are not rewritten. Currently, for bridged packets undergoing VXLAN encapsulation, the DSCP in the outer IP header is derived from TC and the ECN bits are set to zero. The desired behavior is that the outer IP header should be remarked with ingress packet DSCP and ingress packet ECN. Also, local congestion should be handled correctly.

Dynamic Explicit Congestion Notification (D-ECN) configures an ECN marking threshold that changes dynamically based on a transmit queue’s available shared buffers. A D-ECN offset and D-ECN floor is configured per unicast transmit queue which defines how the ECN marking threshold will change as the queue’s shared buffer limit changes.

This feature supports counting ECN marked packets on a per egress port per tx queue basis. The

ECN (Explicit Congestion Notification) is a mechanism of notifying network congestion without dropping the packets. The ECN based network congestion notification can be done in two ways: queue-length based ECN, latency based ECN. The queue-length based ECN marks the ECN-Capable Transport (ECT) packets when the average VOQ length exceeds the configured ECN threshold value whereas latency based ECN notify the congestion by marking the ECT packets, if packets take longer than the configured threshold to get dequeued from the VOQ. Both result in the egress marking of the packet if the congestion experienced is beyond the threshold.