Forwarding Plane Commands
Page 462 7750 SR OS Interface Configuration Guide
• AF as the highest forwarding class mapped
And the forwarding plane on the IOM3-XP is configured with the following WRED limits:
• Current WRED mega-pool is sized at 500Kbytes
• AF MBS oversubscription factor is 2 (2:1)
The system will increase the WRED mega-pool size to 505Kbytes (increase of 10Kbytes/2) as long
as the maximum buffer allocation percentage equates to a value equal to or greater than 505Kbytes.
(If not, the WRED mega-pool will be capped at the maximum level.)
The no form of the command immediately restores the default min and max percentage values for
sizing the WRED mega-pool.
Parameters min percent-of-total — This required keyword defines the minimum percentage of total IOM3-XP
queue buffers that will be applied to the WRED mega-pool. The value given for percent-of-total
must be less than or equal to the value given for the max percent-of-total. Percentages are
defined with an accuracy of hundredths of a percent in the nn.nn format (15.65 = 15.65%).
Values 0.00 — 99.99
Default 25.00
max percent-of-total — This required keyword defines the maximum percentage of total IOM3-XP
queue buffers that may be applied to the WRED mega-pool. The value given for percent-of-total
must be greater than or equal to the value given for the min percent-of-total. Percentages are
defined with an accuracy of hundredths of a percent in the nn.nn format (15.65 = 15.65%).
Values 0.01 — 99.99
Default 25.00
resv-cbs
Syntax resv-cbs min percentage max percentage
no resv-cbs
Context config>card>fp>egress>max-wred-control
Description This command defines the amount of IOM3-XP buffers within the WRED mega-pool that will be set
aside for WRED queues operating within their configured CBS thresholds. Note that the min
percentage and max percentage parameters must be set to the same value. The IOM3-XP protects
against WRED queue buffer starvation by setting aside a portion of the buffers within the WRED
mega-pool. The WRED queue CBS threshold defines when a WRED queue requests buffers from
reserved portion of the WRED mega-pool and when it starts requesting buffers from the shared
portion of the mega-pool. With proper oversubscription provisioning, this prevents a seldom active
queue from being denied a buffer from the mega-pool when the shared portion of the mega-pool is
congested. Further control over shared congestion is defined later in this document under the slope-
policy command.
The WRED mega-slope reserve CBS size is controlled in the same manner as the overall sizing of the
WRED mega-pool. A min and max parameter is provided to scope the range that the reserved portion
based on percentages of the WRED mega-pool current size. Forwarding class cbs-factor settings are
used in the same way as the mbs-factor parameters to move the actual reserved size between the
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