TOI Author :: Tanuj Kumar Jhamb

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.

sFlow is a sampling technique which monitors incoming traffic on all interfaces without affecting network performance. Egress sFlow is a feature which samples the packets in the egress pipeline for analytical purposes. Currently egress sFlow is only software based on Arista switches.

WRED ( Weighted Random Early Detection ) is one of the congestion management techniques. It works at queue level to drop ECN capable and non ECN capable traffic randomly after reaching the given queue threshold even before the queue is full.

sFlow is a sampling technique which monitors incoming traffic on all interfaces without affecting network performance. Egress sFlow is a feature which samples the packets in the egress pipeline for analytical purposes. Currently egress sFlow is only software based on Arista switches.

sFlow is a sampling technique which monitors the incoming traffic on all the interfaces without affecting the network performance.

With the use of MAC ACL configuration, match on ethertype can be programmed under QoS class-map configuration which will help customers to classify the control traffic based on ethertype (e.g. PPPoE discovery (0x8863) / session (0x8864) stage ) along with match on sub protocol (LCP/IPCP/PAP/CHAP) which is present in the payload.

The flow-label match for QoS policy map can be achieved by using the TCAM profile “qos-match-ipv6-flow-label” which is available from EOS 4.27.2F onwards. 

This feature allows the user to match the 20 bit IPV6 flow label using the Qos Policy Map and allows to classify the flow-label controlled traffic.

This feature allows the user to configure upto 1023 unique QoS Policy-maps per chip.

Support for matching of DSCP / ECN is available under the QOS class map configuration on Arista switches.