In 2009, Microsoft released the first version of the Application Request Routing (ARR) module, which plugs into IIS 7.0 or greater and functions as a reverse proxy load balancer. This is an elegant solution because of its quick and clean installation and rich functionality. When looking for a load-balancing solution, ARR is worth serious consideration.
ARR leverages URL Rewrite for the routing, giving it powerful functionality for routing decisions. And because it sits on top of IIS, all the site bindings, security, error handling, and other rich functionality are readily available.
You may have heard ARR described as a reverse proxy, which technically is true; however, that description alone downplays its significance. ARR functions as a full-blown load balancer as long as your requirements fit within ARR's feature set.
Following are the main advantages of ARR: