Microsoft Application Request Routing (ARR) Version 1 for IIS 7 enables Web server administrators and hosting providers and to increase Web application reliability and scalability through rule-based routing and load balancing of HTTP server requests. With ARR, administrators can optimize resource utilization for application servers to reduce management costs for Web farms and shared hosting environments.
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 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.
Features
- 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
Awards
Application Request Routing 1.0

Or, download x86 / x64
Application Request Routing v2.0 Beta is an incremental release that includes all the features from version 1.0. In addition, the beta adds a support for disk based cache. More specifically, v2.0 Beta can be used to:
- Enhance ARR v1.0 scenarios with disk cache.
- Use ARR as a cache proxy as an edge cache.
Learn More about the beta.