Michael Hayes, president of Coyote Point Systems (http://www.coyotepoint.com/), says:

There is an ongoing debate in the networking industry: What do you call a device that sits in front of servers to ensure high availability and accelerate traffic like the Coyote Point Equalizer? Oddly enough, the answer isn’t straightforward.

If you ask most anyone in the data center they’d call it a server load balancer, or load balancer for short. However, if you ask an industry analyst (and some vendors), they’d use the term application delivery controller or ADC. So which is it?

If you use the term “load balancer”, anyone from a server administrator to network administrator to application developer, they will likely know what you mean. They know it means some sort of appliance device that sits in front of a group of servers and distributes inbound traffic. They may even know some of the more sophisticated functions these devices can provide, such as SSL acceleration and URL parsing. They may not know the ins and outs, but typically they’ll have a pretty good idea of what a load balancer entails. Since load balancers are used in front of virtually every website, they’ve probably worked with one or at least worked in an environment where one is employed.

There are some that believe (with valid reasoning) that load balancer is an outdated term, that the current generation of devices available from Coyote Point and other vendors go beyond the load balancers that appeared in the late 1990s (Coyote Point is one of the first vendors). Where as the devices from the late ‘90s were basic Layer 4 devices, today’s devices can perform all manner of Layer 7 functionality, SSL acceleration, integrate with virtual environments, and more.

There are others who prefer the older term load balancer. They would argue that the term application delivery controller isn’t widely known and can cause confusion in the data center as well as the marketplace. The devices of today, while far more advanced than those that came out 15 years ago, are a natural evolution of the products and still serve the basic functions (i.e. load balancing).

Certainly the term load balancer is more popular, and chances are if searched on Google it was for the term “load balancer” and not “ADC.” But ADC perhaps more accurately reflects the capabilities of our Equalizer line.

Which leads us to a conundrum: Do you call the Coyote Point Equalizer a load balancer or an application delivery controller? The name isn’t as important as the features and benefits provided. So the industry calls them both a load balancer and an ADC. No one will correct you if you use one term or the other, and vendors’ literature will often reflect both terms. Coyote Point believes that this terminology is an area where reasonable people can disagree, and the introduction of our new enterprise-class EQ/OS 10 platform architecture blurs the distinction between load balancer and application delivery controller even further.

At the end of the day it is obvious that people use the terms interchangeably. What the customer must really look at is how the technology contributes to their requirements for delivering applications. Whether you’re looking for an application delivery controller, a load balancer or simply a solution to ensure that your website is always available and responsive, Coyote Point delivers.