This read-only Counter64 counts the cumulative number of bytes discarded by WRED, Weighted Random Early Detection, congestion avoidance for this row's traffic class. An admin uses this to see how much data WRED is proactively dropping to avoid queue saturation, before packets would otherwise be tail-dropped. For example, an increasing zxr10QosStatBytesWREDDrop count on a "best-effort" class shows WRED is actively pre-emptively shedding some of that class's traffic to prevent a full tail-drop event.