D-Link DGS-3630 User Manual 1 - Page 436

DGS-3630 Series Layer 3 Stackable Managed Switch Web UI Reference Guide To view the following window, click QoS > Basic Settings > Port Scheduler Method, as shown below: Figure 7-2 Port Scheduler Method Window The fields that can be configured are described below: Parameter Unit From Port - To Port Scheduler Method Description Select the Switch unit that will be used for this configuration here. Select the range of ports that will be used for this configuration here. Select the scheduler method that will be applied to the specified port(s). Options to choose from are Strict Priority (SP), Round-Robin (RR), Weighted Round-Robin (WRR), and Weighted Deficit Round-Robin (WDRR). By default, the output queue scheduling algorithm is WRR. • Strict Priority (SP) specifies that all queues use strict priority scheduling. It provides strict priority access to the queues from the highest CoS queue to the lowest. • Round-Robin (RR) specifies that all queues use round-robin scheduling. It provides fair access to service a single packet at each queue before moving on to the next one. • Weighted Round-Robin (WRR) operates by transmitting permitted packets into the transmit queue in a round robin order. Initially, each queue sets its weight to a configurable weighting. Every time a packet from a higher priority CoS queue is sent, the corresponding weight is subtracted by 1 and the packet in the next lower CoS queue will be serviced. When the weight of a CoS queue reaches zero, the queue will not be serviced until its weight is replenished. When weights of all CoS queues reach 0, the weights get replenished at a time. • Weighted Deficit Round-Robin (WDRR) operates by serving an accumulated set of backlogged credits in the transmit queue in a round robin order. Initially, each queue sets its credit counter to a configurable quantum value. Every time a packet from a CoS queue is sent, the size of the packet is subtracted from the corresponding credit counter and the service right is turned over to the next lower CoS queue. When the credit counter drops below 0, the queue is no longer serviced until its credits are replenished. When the credit counters of all CoS queues reaches 0, the credit counters will be replenished at that time. All packets are serviced until their credit counter is zero or negative and the last packet is transmitted completely. When this condition happens, the credits are replenished. When the credits are replenished, a quantum of credits are added to each CoS queue credit counter. The quantum for each CoS queue may be different based on the user configuration. To set a CoS queue in the SP mode, any higher priority CoS queue must also be in the strict priority mode. Click the Apply button to accept the changes made. 424