D-Link xStack DXS-3350SR Installation & User Manual - page 102
DXS-3350SR Gigabit Layer 3 Switch
Configuring The Combination Queue
Utilizing the QoS Output Scheduling Configuration window shown above, the DXS-3350SR can implement a
combination queue for forwarding packets. This combination queue allows for a combination of strict and weight-fair
(weighted round-robin “WRR”) scheduling. To set the combination queue, enter a 0 for the Max Packets entry of the
corresponding priority queues listed in the window above. Priority queues that have a 0 in the Max Packetfield will
forward packets with strict priority scheduling. The remaining queues, that do not have a 0 in their Max Packet field, will
follow a weighted round-robin (WRR) method of forwarding packets — as long as the priority queues with a 0 in their Max
Packetfield are empty. When a packet arrives in a priority queue with a 0 in its Max Packet field, this queue will
automatically begin forwarding packets until it is empty. Once a priority queue with a 0 in its Max Packet field is empty,
the remaining priority queues will reset the weighted round-robin (WRR) cycle of forwarding packets, starting with the
highest available priority queue. Priority queues with an equal level of priority and equal entries in their Max Packet field
will empty their fields based on hardware priority scheduling. The Max Packet parameter allows you to specify the
maximum number of packets a given priority queue can transmit per weighted round-robin (WRR) scheduling cycle. This
provides for a controllable CoS behavior while allowing other queues to empty as well. A value between 0 and 15 packets
can be specified per priority queue to create the combination queue.
The example window below displays an example of the combination queue where Class-1 will have a strict priority for
emptying its queue, while the other classes will follow a weight fair scheduling.
Figure 6- 45. QoS Output Scheduling Configuration window – Combination queue example
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