Microsoft Application Request Routing for IIS 7

The Microsoft Application Request Routing for IIS7 was designed to be a proxy based routing module that forwards HTTP requests to content servers based on HTTP headers and server variables, and load balance algorithms.

By taking advantage of Application Request Routing, administrators have the ability to create powerful routing rules based on URL, HTTP headers and server variables to determine the most appropriate Web application server for each request. ARR makes request routing decisions at the application level, and can be used in conjunction with hardware load balancers as an added layer of control over HTTP requests. For example, using the Application Request Router, administrators are able to route all *.aspx requests to a dynamic group of dedicated Web application servers, which can scale up and down based on traffic demands, while requests for video content, images, javascript and other static content can be served from the ARR machine, or a separate group of servers.

Administrators can use IIS7 and the Application Request Routing feature on a reduced-footprint Windows Server core machine(s) to handle incoming requests, and then place traditional Web Application Servers on a middle tier of machines, which can protected behind additional firewalls and not exposed directly to the internet. This protects feature-rich Web application servers from being directly exposed to internet hacking attempts, and enables to scale-out cpu-intensive Web application servers independently.

ARR lets administrators create, manage, and apply load balancing rules to server farms in IIS 7.0 Manager. Administrators can then easily add or remove servers from a server farm to match demand throughput without impacting application availability. ARR also includes live traffic and URL test monitoring capabilities to determine the health of individual servers and configuration settings, while allowing administrators to view aggregated runtime statistics in IIS 7.0 Manager.

Optimize and scale server capacity through client and host name affinity Administrators can use ARR to route all requests from a specific client to a specific Web application server in a server farm by creating an affinity between the client and server. ARR includes the ability to differentiate clients behind Network Address Traversal (NAT) firewalls and hardware load-balancers, so each client is treated independently. Host name affinity lets hosting providers optimize resources per server and offer scaled solutions by routing requests to servers based on host name.