Microsens MS453490M Management Guide - Manual (Page 818)

C HAPTER 35 | Class of Service Commands
Priority Commands (Layer 2)
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queue mode This command sets the scheduling mode used for processing each of the
class of service (CoS) priority queues. The options include strict priority,
Shaped Deficiit Weighted Round-Robin (SDWRR), or a combination of strict
and weighted queuing. Use the no form to restore the default value.
S YNTAX
queue mode {strict | wrr | strict-wrr [queue-type-list]}
no 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 - Shaped Deficit Weighted Round-Robin shares bandwidth at
the egress ports by using scheduling weights (based on the queue
weight command), and servicing each queue in a round-robin
fashion.
strict-wrr - Strict priority is used for the high-priority queues and
SDWRR for the rest of the queues.
queue-type-list - Indicates if the queue is a normal or strict type.
(Options: 0 indicates a normal queue, 1 indicates a strict queue)
D EFAULT S ETTING
Strict and WRR, with Queue 3 using strict mode
C OMMAND M ODE
Global Configuration
C OMMAND U SAGE
◆ The switch can be set to service the port queues based on strict
priority, SDWRR, or a combination of strict and weighted queueing.
◆ Strict priority requires all traffic in a higher priority queue to be
processed before lower priority queues are serviced.
◆ The SDWRR algorithm used by this switch is known as Shaped Deficit
Weighted Round Robin (SDWRR).
The basic WRR algorithm uses a 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.
Deficit Weighted Round-Robin (DWRR) services the queues in a manner
similar to WRR, but the next queue is serviced only when the queue’s
Deficit Counter becomes smaller than the packet size to be transmitted.
As a result, traffic on queues with large weights cause increased latency
and jitter for traffic waiting for scheduling on other queues. In SDWRR,
if two or more queues have traffic eligible for transmission (i.e., the
Deficit Counter is greater than the packet size to be transmitted), then
a round-robin scheme among those queues is used, while still