CoS Explicit congestion notification (ECN)

Enables end-to-end congestion notification between two endpoints on TCP/IP based networks. ECN must be enabled on both endpoints and on all of the intermediate devices between the endpoints for ECN to work properly. Any device in the transmission path that does not support ECN breaks the end-to-end ECN functionality. ECN notifies networks about congestion with the goal of reducing packet loss and delay by making the sending device decrease the transmission rate until the congestion clears, without dropping packets. RFC 3168, The Addition of Explict Congestion Notification (ECN) to IP, defines ECN. You can configure ECN based on buffer occupancy at the egress interface or on packet latency between the ingress and egress interface.