Computed targets

With XML load objects, the target load and capacity can be supplied in the load object (optional), as an XML load object can report just the current load. When you use non-XML load objects or download score based load balancing, only the current load is reported and Global Traffic Management computes the target and capacity as follows:
  • You configure each property with a traffic weight per data center. For example, for an even split between two data centers you might give each data center a weight of 1. Global Traffic Management normalizes the two weights, splitting them evenly (0.5 and 0.5) across the data centers so they total 1.
  • Global Traffic Management collects the load information (either from load objects or from liveness test download scores) and sums the load across all data centers for a property. It then multiplies this sum by the load imbalance factor to get a total target load and computes each data center's target by multiplying the total target by the data center's normalized weight.
For example, if you have two data centers configured for an equal traffic split, and you are using download score based load balancing, and your load imbalance factor is 1.25, and data center A is reporting download times of 1 second while data center B is reporting download times of 4 seconds, then:
  • The total load is 5.
  • The total target load is 6.25 (5 * 1.25).
  • The target load for each data center is 3.125 (half of 6.25).

This puts data center B over its target load and data center A under its target load, so Global Traffic Management attempts to shift some traffic from data center B to data center A.

If you configure your property for Performance-Based Load Balancing with Load Feedback Based on Liveness Test Download Scores or Performance-Based Load Balancing with Load Feedback (targets computed from configured weights) , the computed-targets flag for your property is set automatically.