When pool per queue mode is used, the queue resides in its own pool that 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: WRED queue: pool-per-queue mode.
The queue pools take buffers from the WRED egress megapool that 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>The buffer allocation determines how much of the egress normal megapool is allocated for the egress WRED megapool, with the resv-cbs defining the amount of reserved buffer space in the egress WRED megapool. In both cases, the min and max values must be equal. The slope-policy defines the WRED slope parameters and the time average factor used on the megapool to handle congestion as the megapool buffers are used. The no shutdown command enables the megapool. The megapools on card 1 fp 1 can be shown as follows:
*A:PE# show megapools 5 fp 1
===============================================================================
MegaPool Summary
===============================================================================
Type Slot-FP App. Pool Name Actual ResvCBS PoolSize
Admin ResvCBS
-------------------------------------------------------------------------------
fp 5-1 Egress normal n/a 282624
n/a
fp 5-1 Ingress normal n/a 374784
n/a
fp 5-1 Egress wred 24576 93696
25%
===============================================================================
*A:PE#
To configure a pool per queue, the wred-queue command is used under queue in a SAP egress QoS policy or egress queue group template with the mode set to pool-per-queue as follows:
qos
queue-group-templates
egress
queue-group <queue-group-name> create
queue <queue-id> create
wred-queue [policy <slope-policy-name>] mode pool-
per-queue
slope-usage default
exit
exit
exit
exit
sap-egress <policy-id> create
queue <queue-id> [<queue-type>] [create]
wred-queue [policy <policy-name>] mode pool-per-queue
slope-usage default
exit
exitCongestion control is provided by the slope policy applied to the queue, with the slopes to be used having been no shutdown (otherwise traffic uses the MBS drop tail or a megapool slope). The slope-usage defines the mapping of the traffic profile to the WRED slope and only default is allowed with pool-per-queue that gives the following mapping:
Inplus-profile maps to the highplus slope.
In-profile maps to the high slope.
Out-of-profile maps to the low slope.
Exceed-profile maps to the exceed slope.
For example, the following SAP egress QoS policy is applied to SAP on an FP with the egress WRED megapool enabled:
sap-egress 10 create
queue 1 create
wred-queue policy "slope1" mode pool-per-queue
slope-usage default
exit
exitThe details of both the megapool and queue pool usages can then be shown using the show megapools command (detailed version):
*A:PE# show megapools 5 fp 1 wred service-id 1
===============================================================================
MegaPool Information
===============================================================================
Slot : 5 FP : 1
Application : Egress Pool Name : wred
Resv CBS : 25%
-------------------------------------------------------------------------------
Utilization State Start-Avg Max-Avg Max-Prob
-------------------------------------------------------------------------------
HiPlus-Slope Down 85% 100% 80%
High-Slope Down 70% 90% 80%
Low-Slope Down 50% 75% 80%
Exceed-Slope Down 30% 55% 80%
Time Avg Factor : 7
Pool Total : 93696 KB
Pool Shared : 69120 KB Pool Resv : 24576 KB
Pool Total In Use : 0 KB
Pool Shared In Use : 0 KB Pool Resv In Use : 0 KB
WA Shared In Use : 0 KB
HiPlus-Slope Drop Pr*: 0 Hi-Slope Drop Prob : 0
Lo-Slope Drop Prob : 0 Excd-Slope Drop Prob : 0
===============================================================================
Queue : 1->5/1/1:1->1
===============================================================================
FC Map : be l2 af l1 h2 ef h1 nc
Dest Tap : not-applicable Dest FP : not-applicable
Admin PIR : 10000000 Oper PIR : Max
Admin CIR : 0 Oper CIR : 0
Admin MBS : 12288 KB Oper MBS : 12288 KB
High-Plus Drop Tail : not-applicable High Drop Tail : not-applicable
Low Drop Tail : not-applicable Exceed Drop Tail : not-applicable
CBS : 0 KB Depth : 0
Slope : slope1
WRED Mode : pool-per-queue Slope Usage : default
Time Avg Factor : 7
-------------------------------------------------------------------------------
HighPlus Slope Information
-------------------------------------------------------------------------------
State : enabled
Start Average : 10752 KB Max Average : 12288 KB
Max Probability : 80 % Curr Probability : 0 %
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
High Slope Information
-------------------------------------------------------------------------------
State : enabled
Start Average : 9408 KB Max Average : 10944 KB
Max Probability : 80 % Curr Probability : 0 %
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Low Slope Information
-------------------------------------------------------------------------------
State : enabled
Start Average : 6144 KB Max Average : 9216 KB
Max Probability : 80 % Curr Probability : 0 %
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Exceed Slope Information
-------------------------------------------------------------------------------
State : enabled
Start Average : 3648 KB Max Average : 6720 KB
Max Probability : 80 % Curr Probability : 0 %
-------------------------------------------------------------------------------
===============================================================================
===============================================================================
* indicates that the corresponding row element may have been truncated.
*A:PE#
Each WRED pool-per-queue uses a WRED pool resource on the FP. The resource usage is displayed in the tools dump resource-usage card [slot-num] fp [fp-number] command output under the Dynamic Q2 WRED Pools header.