D-Link DGS-1510 Series Web Ui Reference Manual page 158

DGS-1510 Series Gigabit Ethernet SmartPro Switch Web UI Reference Guide
To view the following window, click QoS > Basic Settings > Port Scheduler Method, as shown below:
The fields that can be configured are described below:
Parameter
Unit
From Port / To Port
Scheduler Method
Figure 7-2 Port Scheduler Method window
Description
Select the switch unit that will be used for this configuration here.
Select the appropriate port range used for the 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.
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.
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
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