Reference Guide

730 | Quality of Service (QoS)
www.dell.com | support.dell.com
To allocate bandwidth to queues on the C-Series and S-Series, assign each queue a weight ranging from 1
to 1024, in increments of 2
n
, using the command bandwidth-weight. Table 35-3 shows the default
bandwidth weights for each queue, and their equivalent percentage which is derived by dividing the
bandwidth weight by the sum of all queue weights.
There are two key differences between allocating bandwidth by weight on the C-Series and S-Series and
allocating bandwidth by percentage on the E-Series:
1. Assigning a weight to one queue affects the amount of bandwidth that is allocated to other queues.
Therefore, whenever you are allocating bandwidth to one queue, Dell Force10 recommends that you
evaluate your bandwidth requirements for all other queues as well.
2. Because you are required to choose a bandwidth weight in increments of 2
n
you may not be able to
achieve exactly a target bandwidth allocation.
Table 35-4 shows an example of choosing bandwidth weights for all four queues to achieve a target
bandwidth allocation.
Specify WRED drop precedence
Specify WRED drop precedence is supported only on platform e z
Note: Dell Force10 recommends assigning bandwidth to all queues. If queues are left un-allocated, the
remaining bandwidth is shared equally among the un-allocated queues. If the sum of the allocated
bandwidth percentage exceeds 100% 1% from the allocated queues will be assigned to each un-allocated
queues.
Table 35-3. Default Bandwidth Weights for C-Series and S-Series
Queue Default Weight
Equivalent
Percentage
0 1 6.67%
1 2 13.33%
2 4 26.67%
3 8 53.33%
Table 35-4. Assigning Bandwidth Weights for the C-Series and S-Series
Queue Weight
Equivalent
Percentage Target Allocation
0 1 0.44% 1%
1 64 28.44% 25%
2 128 56.89% 60%
3 32 14.22% 14%