FTOS Configuration Guide for the C-Series - Force10 Networks

Configure policy-based rate shaping
Rate shape egress traffic using the command rate-shape from QOS-POLICY-OUT mode.
Allocate bandwidth to queue
To allocate an amount bandwidth to a queue using the command bandwidth-percentage on the E-Series.
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 53 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.
Table 53 Default Bandwith Weights for C-Series and S-Series
Queue Default Weight
Equivalent
Percentage
1 1 6.67%
2 2 13.33%
3 4 26.67%
4 8 53.33%
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, 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
acheive exaclty a target bandwidth allocation.
Table 54 shows an example of choosing bandwidth weights for all four queues to acheive a target
bandwidth allocation.
Table 54 Assigning Bandwidth Weights for the C-Series and S-Series
Queue Weight
Equivalent
Percentage
Target
Allocation
1 1 0.44% 1%
2 64 28.44% 25%
3 128 56.89% 60%
4 32 14.22% 14%
570 Quality of Service