IIS7 Request Routing and Load Balancer Release Candidate Available for Download

I’m excited to announce that IIS has released a Release Candidate of the new IIS7 Application Request Routing (ARR) extension!  ARR enables Web server administrators to easily scale-out Web applications and improve reliability through HTTP-level, rule-based routing and load balancing.  Read more about the cool new features in this new release and check out the updated documentation.

Download the RC release:



For those who are new to IIS7’s ARR module, here are the benefits it provides:

Balance loads more efficiently across servers to maximize resource utilization

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.

Increase Security and Scalability of Application 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.

Manage and monitor multiple server farms more easily through IIS Manager

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 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.


  • HTTP based routing decisions built using rules that examine HTTP request information
  • Sophisticated load balancing algorithms to determine appropriate servers to service the HTTP requests
  • Health monitoring for live traffic and specific URLs to determine the health of servers with a set of configuration parameters provided to calibrate baseline server health
  • Client affinity to direct all requests from a client to a specific server by using cookies.
  • Host name affinity to streamline administration for Web servers and to create additional business opportunities.
  • Management of multiple server farms to enable pilot management and A/B testing scenarios.
  • Management and monitoring of all configuration settings and aggregated runtime statistics through IIS Manager interface.
  • Support for Failed Request Tracing Rules

1 Comment

  • Isn't this just what you would do with an F5?, not sure I like the idea of the "web server" being responsible for routing, LB, HA, etc.

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