Alcatel-Lucent 7750 SR OS Interface Configuration Manual page 463

minimum and maximum thresholds according to appropriate oversubscription factors that are applied
to the sum of the WRED queue CBS values.
When min and max are defined as the same value, the WRED mega-pool size will not fluctuate and
the oversubscription factors will have no effect.
FC CBS Oversubscription Factors and WRED CBS Reserve Sizing
Each WRED queue in a SAP egress QoS policy is created on an egress IOM3-XP when the policy is
applied to an egress SAP on the IOM and at least one forwarding class is mapped to the queue. For
WRED queue CBS buffer management purposes, each forwarding class is configured with a CBS
oversubscription factor (OSF) on the IOM using the osf command. The CBS oversubscription factor
is used by the system as a provisioning parameter that defines the acceptable level of oversubscription
between the sum of the committed buffer sizes (CBS) of the WRED queues for a given class and the
number of buffers for that class that should be placed in the WRED mega-pool CBS reserve. Since
multiple forwarding classes may be mapped to the same queue, the oversubscription factor associated
with the highest forwarding class mapped is used for dynamically sizing the WRED mega-pool CBS
reserve.
As an example, when a WRED queue is configured with the following attributes:
And the forwarding plane on the IOM3-XP is configured with the following WRED limits:
The system will increase the WRED mega-pool CBS reserve size to 103Kbytes (increase of 6Kbytes/
2) as long as the maximum buffer allocation percentage for resv-cbs equates to a value equal to or
greater than 103Kbytes. (If not, the WRED mega-pool CBS reserve will be capped at the maximum
level.)
The no form of the command immediately restorse the default min and max percentage values for
sizing the WRED mega-pool CBS reserve.
Parameters
min percent-of-total — This required keyword defines the minimum percentage of the IOM3-XP
max percent-of-total — This required keyword defines the maximum percentage of the IOM3-XP
7750 SR OS Interface Configuration Guide
• CBS equal to 6Kbytes
• AF as the highest forwarding class mapped
• Current WRED mega-pool CBS reserve is sized at 100Kbytes
• AF CBS oversubscription factor is 2 (2:1)
WRED mega-pool buffers that will be applied to the CBS reserve. The value given for percent-
of-wred must be less than or equal to the value given for the max percent-of-wred. 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
WRED mega-pool buffers that may be applied to the CBS reserve. The value given for percent-
of-wred must be greater than or equal to the value given for the min percent-of-wred.
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
Interface Configuration
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