QoS Policies
Quality of Service Guide 31
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Pool per Queue Mode
When pool per queue mode is used, the queue resides in its own pool which is located in the
forwarding plane egress megapool. The size of the pool is the same as the size of the queue
(based on the MBS), consequently the WRED slopes operating on the pool's buffer utilization
are reacting to the congestion depth of the queue. The size of the reserved CBS portion of the
buffer pool is dictated by the queue's CBS parameter. This is shown in Figure 2.
Figure 2: WRED queue: pool-per-queue mode
The queue pools take buffers from the WRED egress megapool which must be enabled per
FP; if this megapool is not enabled, the queue operates as a regular queue. By default only the
Ingress normal and Egress normal megapools exist on an FP. The Egress WRED megapool
is configured using the following commands:
configure
card <slot-number>
fp <fp-number>
egress
wred-queue-control
[no] buffer-allocation min <percentage> max
<percentage>
[no] resv-cbs min <percentage> max <percentage>
[no] shutdown
[no] slope-policy <slope-policy-name>
Slopes in WRED queues
operate on the full
WRED pool size (MBS)
Buffers from reserved portion
of WRED megapool
Buffers from shared portion
of WRED megapool
WRED queue
buffer pool
MBS
CBS
Queue
depth
low-slope
hi-slope
exceed-slope
0947
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