Working with Quality of Service
3-DNS® Administrator Guide 8 - 3
•Emphasis
You can adjust coefficients to emphasize one normalized metric over
another. For example, by changing the coefficients to the values shown
in Figure 8.1, you are putting the most emphasis on completion rate.
In the preceding example, if the completion rates for two virtual servers are
close, the virtual server with the best packet rate is chosen. If both the
completion rates and the packet rates are close, the round trip time (RTT)
breaks the tie. In this example, the metrics for Topology, Hops, Link
Capacity, VS Capacity, and Kilobytes/Second modes are not used in
determining how to distribute connections.
Customizing the QOS equation
You can customize the QOS equation globally, meaning that the equation
applies to all wide IPs that use the Quality of Service mode. You can also
customize individual wide IPs, in which case the global QOS equation
settings are overwritten.

To modify global QOS coefficients using the Configuration utility

1. In the navigation pane, click System.
The System - General screen opens.
2. On the toolbar, click Load Balancing.
The System - Load Balancing screen opens.
3. Define the global QOS coefficients in the Round Trip Time,
Completion Rate, Hops, BIG-IP Packet Rate, Topology, Link
Capacity, VS Capacity, and Kilobytes/Second boxes.
4. Click Update.
globals {
qos_coeff_rtt 50
qos_coeff_completion_rate 100
qos_coeff_packet_rate 1
qos_coeff_topology 0
qos_coeff_hops 0
qos_coeff_lcs
qos_coeff_vs_capacity 0
qos_coeff_kbps 0
}
Figure 8.1 QOS coefficients emphasizing completion rate