Alcatel-Lucent 7750 Configuration Manual page 553

visioning parameter that defines the acceptable level of oversubscription between the sum of the maximum
buffer sizes (mbs) of the WRED queues for a given class and the number of buffers for that class in the
WRED mega-pool. Since multiple forwarding classes may be mapped to the same queue, the oversubscrip-
tion factor associated with the highest forwarding class mapped is used for dynamically sizing the WRED
mega-pool.
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 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
Default
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
Default
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
7750 SR Interface Configuration Guide
MBS equal to 10Kbytes
AF as the highest forwarding class mapped
Current WRED mega-pool is sized at 500Kbytes
AF MBS oversubscription factor is 2 (2:1)
0.00 — 99.99
25.00
0.01 — 99.99
25.00
Interface Configuration
Page 553