QoS EF packet loss occurring when link switchover but from DMS performance picture checking, there is no congestion.
When use command line to check the PoS link usage each 10 seconds, we find there is congeston in the link which cause the EF packet loss.
For the detail please check the attachment.
The QoS queuing drops packets only when the queuing faces congestion, no matter with the PoS link up/down. The DMS can just detect the link usage each 30 minutes. So from DMS performance picture we can not see the congestion. But when use command line to check the link usage each 10 seconds, we find there is congeston in the link.