Performance without load feedback

Load Feedback is a method by which GTM can obtain real-time information about the load on your data centers to improve its load balancing. Unlike other methods, Load feedback can provide more accurate load balancing on data centers. However, it requires careful configuration that involves building a load object that reports load feedback load resource data to GTM periodically.

GTM uses information on the data center's current load, target load, and maximum capacity to optimize traffic, to ensure that all data centers have a current load below the target load and to prevent current load from exceeding capacity, if possible.

Load Feedback adheres to the following basic principles:
  • Load values must react instantly to the traffic balancing that GTM makes
  • Load must decrease when traffic volume discreases. Likewise, load must increase when traffic volume increases.
  • Load values must not change except in response to traffic directed to the data center by GTM or for that property.

If you cannot provide load feedback, you can configure Global Traffic Management to load balance without it. This mode relies heavily on the nameserver demand estimates (see Nameserver demand estimation), based on how often nameservers revisit Traffic Management nameservers to refresh cached DNS resolutions. GTM attempts to assign traffic so that the sum of the nameserver demands allocated to each of your data centers respects the traffic weights you configured, subject to the leeway allowed by the load imbalance factor. This method works best for properties that have large user populations distributed widely throughout the world. It does not work so well for very small or concentrated user populations.

Important points to remember about load balancing without load feedback are:
  • It is based purely on historical estimates of client demand behind nameservers.
  • It does not take into account daily load fluctuations.
  • It cannot take into account anomalies such as a large ISP deploying a new nameserver serving thousands of clients, as it can take a week or more for new nameserver loads to propagate through NSD.

If you require precise load balancing that reacts quickly to changing loads, consider using load feedback.