QoS Queue Group Template Command Reference
458 Quality of Service Guide
This implements each queue in its own pool and uses the WRED capabilities of the pool to
provide WRED per queue. This is supported on both FP2 and later hardware and is configured
with the pool-per-queue keyword.
Native Hardware WRED
When the wred-queue mode native command is configured, the queue uses the WRED capabilities of
the FP3. In this case the out and exceed profile traffic map to the low and exceed WRED slopes
specified within the slope policy, and the in profile traffic uses the MBS drop tail; this requires the
slope-usage to be configured as exceed-low. The instantaneous queue depth is compared against the
low and exceed slopes so the time average factor in the slope policy is ignored.
When a policy is not explicitly defined, the default slope policy is used.
When native mode is enabled for a queue, the hi-low-prio-only and high-prio-only commands are
ignored; traffic mapped to a slope which is shutdown will use the MBS drop tail.
This is only supported on FP3 hardware and is ignored on FP1 and FP2 hardware.
The no form of the command restores the queue default congestion control behavior to the queue.
Pool-per-queue WRED
When the wred-queue mode pool-per-queue command is defined and the queue ID is created on FP2
or higher based hardware, a buffer pool is created specifically for the queue and the queue obtains all
buffers from that pool. The size of the pool is the same as the size of the queue. In this manner, the
WRED slopes that operate based on the pool’s buffer utilization are also reacting to the congestion
depth of the queue.
The size of the buffer pool is dictated by the queue’s mbs parameter. The size of the reserved CBS
portion of the buffer pool is dictated by the queue’s cbs parameter. The provisioning characteristics of
the mbs and cbs commands are not changed.
In the case where this is applied on FP2 or higher based hardware which has WRED queue support
shutdown (config>card>fp>egress>wred-queue-control>shutdown) the queue will continue to map
to either to its default pool or the pool defined in the pool command. If the no shutdown command is
executed in the wred-queue-control context, the queue will at that point be automatically moved to
its own WRED pool.
Each pool created for a queue using the wred-queue command shares buffers with all other wred-
queue enabled queues on the same forwarding plane. The WRED pool buffer management behavior
is defined within the config>card>fp>egress>wred-queue-control CLI context.
The WRED slopes within the pool are defined by the slope policy associated with the queue. When a
policy is not explicitly defined, the default slope policy is used. The slope policy enables, disables and
defines the relative geometry of the high, low, and exceed WRED slopes in the pool. The policy also
specifies the time average factor used by the pool when calculating the weighted average pool depth.
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