5-4z Short packets and long packets are fairly scheduled: if there are both long packets and shortpackets in queues, statistically the short packets should be scheduled preferentially to reduce thejitter between packets as a whole.Compared with FQ, WFQ takes weights into account when determining the queue scheduling order.Statistically, WFQ gives high priority traffic more scheduling opportunities than low priority traffic. WFQcan automatically classify traffic according to the “session” information of traffic (protocol type, TCP orUDP source/destination port numbers, source/destination IP addresses, IP precedence bits in the ToSfield, and so on), and try to provide as many queues as possible so that each traffic flow can be put intothese queues to balance the delay of every traffic flow as a whole. When dequeuing packets, WFQassigns the outgoing interface bandwidth to each traffic flow by precedence. The higher precedencevalue a traffic flow has, the more bandwidth it gets.Additionally, WFQ can work with the minimum guaranteed bandwidth mechanism. You can configure aminimum guaranteed bandwidth for each WFQ queue to guarantee that each WFQ queue isguaranteed of the bandwidth when congestion occurs. The assignable bandwidth (assignablebandwidth = total bandwidth – the sum of the minimum guaranteed bandwidth for each queue) isallocated to queues based on queue priority.For example, assume that the total bandwidth of a port is 10 Mbps, and there are five flows on the portcurrently, with the precedence being 0, 1, 2, 3, and 4 and the minimum guaranteed bandwidth being 128kbps, 128 kbps, 128 kbps, 64 kbps, and 64 kbps respectively.z The assignable bandwidth = 10 Mbps – (128 kbps + 128 kbps + 128 kbps + 64 kbps + and 64 kbps)= 9.5 Mbpsz The total assignable bandwidth quota is the sum of all the (precedence value + 1)s, that is, 1 + 2 +3 + 4 + 5 = 15.z The bandwidth percentage assigned to each flow is (precedence value of the flow + 1)/totalassignable bandwidth quota. The bandwidth percentages for the flows are 1/15, 2/15, 3/15, 4/15,and 5/15 respectively.z The bandwidth finally assigned to a queue = the minimum guaranteed bandwidth + the bandwidthallocated to the queue from the assignable bandwidthBecause WFQ can balance delay and jitter among flows when congestion occurs, it is effectivelyapplied in some special occasions. For example, WFQ is used for the assured forwarding (AF) servicesof the Resource Reservation Protocol (RSVP). In Generic Traffic Shaping (GTS), WFQ is used toschedule buffered packets.SP+WRR queuingBy assigning some queues on the port to the SP scheduling group and the others to the WRRscheduling group (that is, group 1), you implement SP + WRR queue scheduling on the port. Packets inthe SP scheduling group are scheduled preferentially. When the SP scheduling group is empty, packetsin the WRR scheduling group are scheduled. Queues in the SP scheduling group are scheduled withthe SP queue scheduling algorithm. Queues in the WRR scheduling group are scheduled with WRR.Congestion Management Configuration ApproachesComplete the following tasks to achieve congestion management:Task RemarksConfiguring SP Queuing OptionalConfigure WRR Queuing Optional
