Reference Guide

Quality of Service (QoS) | 727
1. Create an output QoS policy using the command qos-policy-output from CONFIGURATION mode.
2. Once you configure an output QoS policy, do one or more of the following
• Configuring policy-based rate shaping
• Configuring policy-based rate shaping
• Allocating bandwidth to queue
• Specifying WRED drop precedence
Configuring policy-based rate shaping:
Rate shape egress traffic using the command rate-shape from QOS-POLICY-OUT mode.
Allocating bandwidth to queue:
The S5000 schedules packets for egress based on Deficit Round Robin (DRR). These strategies both offer
a guaranteed data rate.
To allocate bandwidth to queues on the S5000 assigns each queue a weight ranging from 1 to 1024, in
increments of 2
n
, using the command bandwidth-weight. Table 40-2 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.
The key similarity between allocating bandwidth by percentage and allocating by weight is that assigning a
weight or percentage to one queue affects the amount of bandwidth that is allocated to other queues.
Therefore, whenever you are allocating bandwidth to one queue, Dell Networking recommends that you
evaluate your bandwidth requirements for all other queues as well.
Table 40-3 shows an example of choosing bandwidth weights for all four queues to achieve a target
bandwidth allocation.
Table 40-2. Default Bandwidth Weights for the S5000
Queue Default Weight
Equivalent
Percentage
0 1 6.67%
1 2 13.33%
2 4 26.67%
3 8 53.33%
Table 40-3. Assigning Bandwidth Weights for the S5000
Queue Weight
Equivalent
Percentage
Target
Allocation
0 1 0.44% 1%
1 64 28.44% 25%