When congestion happen the devices have to drop or discard packets and the QoS policies are necessary to be deployed in order to handle this problem and also to avoid congestion.
The NE40 support several alghoritms for congestion avoidance, congestion management, traffic shapping, traffic policing.
1.To manage congestion, NE40-8 can support kinds of queue, usually, we can deploy PQ, CQ, WFQ, CBQ, it depends on the detail requirements to deploy the queues.
2.DS node will select the relative PHB accourding to the DSCP Value. About PHB, well, in NE40-8 routers, PHB has EF,AF,BF based on IETF, and AF can be divide into AF1/AF2/AF3/AF4 also AFij(decide the priority.)