An ADC is an appliance in a datacenter that sits in front of servers to offload the heavy lifting of performance-related tasks. I talk about ADCs in my companion book, Getting Started with XenDesktop® 7.x, Packt Publishing. If you refer back to Chapter 1, XenDesktop® Architecture, in this book, and look at the network diagram, you can see Citrix NetScaler as the frontend to the XenDesktop site.
There are many vendors that supply ADC besides providing SSL to your clients. ADCs are generally a good piece of equipment when it comes to load balancing, caching, compression, and high availability.
A load balancer is a device that acts as a reverse proxy and distributes network and application traffic across a number of servers. A side benefit is that they provide high availability, because, if a server goes down or malfunctions, the load balancer elegantly load balances around it so that no user ever has to encounter a service interruption. The main...