ECS3510-26P_Management Guide R02

C HAPTER 10 | Class of Service
Layer 2 Queue Settings
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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 and
weighted service is used as specified for each queue. Regardless of the
selected mode, the queues are processed sequentially from high to
lower priority (i.e., queues 3 to 0). 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 the queuing mode that uses a combination of strict
and weighted queuing. Service time is allocated to each queue by
calculating a precise number of bytes per second that will be serviced
on each round.
◆ The specified queue mode applies to all interfaces.
PARAMETERS
These parameters are displayed:
◆ 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, servicing each queue in a round-
robin fashion.
■
Strict and WRR – Uses strict or weighted service as specified for
each queue. (This is the default setting.)
◆ Queue ID – The ID of the priority queue. (Range: 0-3)
◆ Strict Mode – If “Strict and WRR” mode is selected, then a
combination of strict and weighted service is used as specified for each
queue. Use this parameter to specify the queues assigned to use strict
priority when using the strict-weighted queuing mode. (Default: Strict
and WRR mode, with Queue 3 using strict mode)