Class of Service
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Instruction Manual - NXA-ENET8-POE+
Selecting the Queue Mode
Use the Traffic > Priority > Queue page to set the queue mode for the egress queues on any interface. The switch can be set to
service the queues based on a strict rule that requires all traffic in a higher priority queue to be processed before the lower priority
queues are serviced, or Weighted Round-Robin (WRR) queuing which specifies a scheduling weight for each queue. It can also be
configured to use a combination of strict and weighted queuing.
Command Usage
Strict priority requires all traffic in a higher priority queue to be processed before lower priority queues are serviced.
WRR queuing specifies a relative weight for each queue. WRR uses a predefined relative weight for each queue that
determines the percentage of service time the switch services each queue before moving on to the next queue. This
prevents the head-of-line blocking that can occur with strict priority queuing.
If Strict and WRR mode is selected, a combination of strict service is used for the high priority queues and weighted service
for the remaining queues. The queues assigned to use strict priority should be specified using the Strict Mode field
parameter.
A weight can be assigned to each of the weighted queues (and thereby to the corresponding traffic priorities). This weight
sets the frequency at which each queue is polled for service, and subsequently affects the response time for software
applications assigned a specific priority value.
Service time is shared at the egress ports by defining scheduling weights for WRR, or one of the queuing modes that use a
combination of strict and weighted queuing.
The specified queue mode applies to all interfaces.
The following table lists the options on this page:
Perform these steps to configure the queue mode:
1.
Click
Traffic
>
Priority
>
Queue
.
2.
Set the queue mode.
3.
If the weighted queue mode is selected, the queue weight can be modified if required.
4.
If the queue mode that uses a combination of strict and weighted queuing is selected, the queues which are serviced first
must be specified by enabling strict mode parameter in the table.
5.
Click
Apply
.
Traffic - Priority (Queue) Options
Queue Mode
• Strict - Services the egress queues in sequential order, transmitting all traffic in the higher
priority queues before servicing lower priority queues. This ensures that the highest priority
packets are always serviced first, ahead of all other traffic.
• WRR - Weighted Round-Robin shares bandwidth at the egress ports by using scheduling
weights, and servicing each queue in a round-robin fashion. (This is the default setting.)
• Strict and WRR - Uses strict priority on the high-priority queues and WRR on the remaining
queues.
Queue ID
The ID of the priority queue. (Range: 0-7)
Strict Mode
If Strict and WRR mode is selected, then a combination of strict service is used for the high priority
queues and weighted service for the remaining queues. Use this parameter to specify the queues
assigned to use strict priority when using the strict-weighted queuing mode. (Default: Disabled)
Weight
Sets a weight for each queue which is used by the WRR scheduler. (Range: 1-127; Default: Weights
1, 2, 4, 6, 8, 10, 12 and 14 are assigned to queues 0 - 7 respectively)
FIG. 132
Setting the Queue Mode (Strict)