Load Balance Page

Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista

Application Request Routing (ARR) uses load balance algorithms to distribute incoming requests between several servers to help you get optimal use of your resources. Use the Load Balance page to configure the load balance settings. For example, if you use a weight algorithm, you can change the load balance weight of the application servers so that requests are evenly distributed or distributed according to customized weights depending on how you want to allocate your resources.

For more information, see the HTTP Load Balancing using Application Request Routing walkthrough.

UI Elements

Element Name Description

Load balance algorithm

Use the list to select the algorithm to use to load balance your server. The available options are:

  • Weighted round robin – Distributes traffic based on the number of incoming requests and their normalized weight. Each server can receive the same distribution of requests or a custom distribution.

  • Weighted total traffic – Distributes traffic based on the size of the requests and responses in bytes. Requests are routed so that the amount of data is load balanced. In an even distribution, the server with the least amount of data will receive the next request.

  • Least current request – Distributes traffic based on the current number of HTTP requests between ARR and each of the application servers. Requests are routed to the server with the least number of current HTTP requests.

  • Least response time – Distributes traffic based on the fastest response time from the servers, which enables the server to respond most quickly.

  • Server variable hash – Distributes traffic based on a hashed value of a server variable.

  • Query string hash – Distributes traffic based on the hashed value of the query string value. When more than one query string name is specified, the concatenated string of the corresponding query string value is used for the hash.

  • Request hash – Distributes traffic based on the hashed value of the configured server variable or URL. For example, if the server variable is QUERY_STRING, the hashed value is based on the names in the request query string.

Load distribution

Use the list to select the method in which to receive requests. The available options are Even distribution or Custom distribution. By default, the weight of the application servers is set to 100, which is an even distribution of traffic. For example, if you have two servers and their weights are both 100/100, then they both receive an equal number of requests. Similarly, if the weight of both servers is 1/1, they will both receive an equal number of requests. Load distribution value sets of 100/100, 5/5, and 1/1 all distribute requests the same way. If you have two servers and the weights are 200/100, 10/5, or 2/1, this means that the first server will receive twice the amount of traffic as the second server. Note that the weights are relative values.

Custom distribution table

Displays the Server Address, % Distribution, and Relative Weight for each server in the list. The distribution percentage is the percentage of traffic that is sent to each server as the relative weight changes. The total distribution must add up to 100 percent. The relative weight is the weight of the server. A higher number indicates that the server will receive more traffic. The default value is 100. You can change this value to any positive integer greater than 0.

Sample duration (seconds)

Specifies the sample duration, in seconds, for the least response time algorithm.

Server variable

Specifies the server variable to use for the server variable hash algorithm. When you start typing, the field will auto-populate to perform a partial match.

Query string names

Specifies the query string names to use for the query string hash algorithm.

Actions Pane Elements

Element Name Description


Applies the selected load balance settings to your server.


Disregards the changes that you have made and resets the settings to the previous values.