Advanced Health Checking

Advanced Health Checking

Advanced health checking is the ability of an ADN to determine not only the state of the server on which an application is hosted, but the status of the application it is delivering. Advanced health checking techniques allow the ADC to intelligently determine whether or not the content being returned by the server is correct and should be delivered to the client.

This feature enables other reliability features in the ADN, such as resending a request to a different server if the content returned by the original server is found to be erroneous.

Load Balancing Algorithms

The load balancing algorithms found in today's ADN are far more advanced than the simplistic round-robin and least connections algorithms used in the early 1990s. These algorithms were originally loosely based on operating systems' scheduling algorithms, but have since evolved to factor in conditions peculiar to networking and application environments. It is more accurate to describe today's "load balancing" algorithms as application routing algorithms, as most ADN employ application awareness to determine whether an application is available to respond to a request. This includes the ability of the ADN to determine not only whether the application is available, but whether or not the application can respond to the request within specified parameters, often referred to as an SLA.

Typical industry standard load balancing algorithms available today include:

* Round Robin
* Least Connections
* Fastest Response Time
* Weighted Round Robin
* Weighted Least Connections
* Custom values assigned to individual servers in a pool based on SNMP or other communication mechanism