666 CHAPTER 61: Q OS CONFIGURATION■ When the queue length is bigger than the upper limit, all inbound packets alldropped.■ When the queue length is in the range of the upper limit and the lower limit,the inbound packets are dropped at random. In this case, a number is assignedto each inbound packet and then compared with the drop probability of thecurrent queue. If the number is bigger than the drop probability, the inboundpacket is dropped. The longer a queue is, the higher the drop probability is.However, there is a top drop probability.QoS Supported by theSwitch 7750Setting Port Priority If an inbound packet is not VLAN-tagged, the switch will tag the packet with thedefault VLAN of the port receiving the packet. In this case, the port priority of theport receiving the packet is assigned to the 802.1p priority of the VLAN tag of thepacket. In this case, you can set the port priority.If the inbound packet is VLAN-tagged, the switch does not perform the operationabove.Configuration prerequisites■ The port whose priority is to be configured is specified■ The priority value of the specified port is specifiedConfiguration procedureTable 531 QoS functions supported by the Switch 7750 and related commandsQoS Description Related commandPriority mapping Support only the mappingbetween 802.1p priority andlocal queuesqoscos-local-precedence-mapPort priority Supported priority priority-levelPriority to be used when apacket enters a queueSupported priority-trustTP Supported traffic-limitPriority remark Supported traffic-priorityRedirect Supported traffic-redirectQueue scheduling Support SP and WRR queue-schedulerRate limit Supported line-rateBandwidth assurance Supported traffic-bandwidthCongestion avoidance Support the RED operation traffic-redTraffic statistics Supported traffic-statisticInbound CAR Supported inboundcar { enable |disable }Traffic-based selective QinQ Supported traffic-remarkTable 532 Set to use the port priorityOperation Command DescriptionEnter system view system-view -
