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The following fields are displayed for all ports/LAGs:
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Interface — Type of interface .
Default CoS — Default VPT value for incoming packets that do not have a
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VLAN Tag . The default CoS is 0 . The default is only relevant for untagged
frames if Trust CoS is selected .
STEP 4 Click Apply . The Running Configuration file is updated .
STEP 5 Click Edit and enter the parameters .
Interface — Select the port or LAG .
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Default CoS — Select the default CoS (Class-of-Service) value to be
assigned for incoming packets (that do not have a VLAN tag) .
STEP 6 Click Apply . The interface default CoS value is saved to Running
Configuration file .
Queue Scheduling
The device supports 4 queues for each interface . Queue number four is the
highest priority queue . Queue number one is the lowest priority queue .
There are two ways of determining how traffic in queues is handled, Strict
Priority and Weighted Round Robin (WRR) .
Strict Priority — Egress traffic from the highest-priority queue is
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transmitted first . Traffic from the lower queues is processed only after the
highest queue has been transmitted, thus providing the highest level of
priority of traffic to the highest numbered queue .
Weighted Round Robin (WRR)—In WRR mode the number of packets sent
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from the queue is proportional to the weight of the queue (the higher the
weight the more frames are sent) . For example, if there are a maximum of
four queues possible and all four queues are WRR and the default weights
are used, queue 1 receives 1/15 of the bandwidth (assuming all queues
are saturated and there is congestion), queue 2 receives 2/15, queue 3
receives 4/15 and queue 4 receives 8 /15 of the bandwidth . The type of
WRR algorithm used in the device is not the standard Deficit WRR (DWRR),
but rather Shaped Deficit WRR (SDWRR) .
The queuing modes can be selected in the Queue Scheduling page . When
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the queuing mode is by strict priority, the priority sets the order in which
queues are serviced, starting with Queue 4 (the highest priority queue)
and going to the next lower queue when each queue is completed . When
the queuing mode is Weighted Round Robin, queues are serviced until
their quota has been used up and then another queue is serviced .
It is also possible to assign some of the lower queues to WRR, while
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keeping some of the higher queues in strict priority . In this case traffic
for the strict priority queues is always sent before traffic from the WRR
queues . Only after the strict priority queues have been emptied is traffic
from the WRR queues forwarded . (The relative portion from each WRR
queue depends on its weight) .
To select the priority method and enter WRR data, do the following .
STEP 1 Click Configuration > Quality of Service > Queue Scheduling .
STEP 2 Enter the parameters .
Queue—Displays the queue number .
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Scheduling Method
Strict Priority—Traffic scheduling for the selected queue and all higher
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queues is based strictly on the queue priority .
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Weighted Round Robin Weight—If WRR is selected, enter the WRR
weight assigned to the queue .
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%WRR Bandwidth—Displays the amount of bandwidth assigned to the
queue . These values represent the percent of the WRR weight .
STEP 3 Click Apply . The queues are configured, and the Running
Configuration file is updated .
Bandwidth Control
The Bandwidth Control page enables users to define two values, Ingress Rate
Limit and Egress Shaping Rate, which determine how much traffic the system
can receive and send .
The ingress rate limit is the number of bits per second that can be received
from the ingress interface . Excess bandwidth above this limit is discarded .
The following values are entered for egress shaping:
Chapter 13 Quality of Service
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