This tool can adjust 3 "hidden" registry settings of Internet Explorer to control caching of DNS records, server connection timeout, and caching of server information.

It can be useful to change these settings to very low values, especially when testing web-servers with quickly changing DNS records / IP addresses. For example in DNS Round Robin or Simple Failover setups.

Internet Explorer does not honor and does not use the TTL (time to live) value provided in DNS records. Instead it caches all DNS records for a fixed period of time (as per this setting) - with one exception:

After Internet Explorer has fetched a web-page, it does not immediately close the TCP connection to the web-server.

By keeping the connection open, following requests to the same web-server can be executed faster. This is known as "keep alive".
This setting affects both DNS caching and server connections ("keep alive") timeouts.

Internet Explorer does not refresh DNS records if another page is requested from the same server domain name within this time interval - even if the DNS Cache Timeout setting has a lower value.
In other words, DNS records timeout according to the higher value of this and the DNS Cache Timeout setting.

However, server connections appear to timeout according to the lower value of this and the Keep Alive Timeout setting.

So for the most predictable results, the value of this setting should be set lower than or equal to the DNS Cache Timeout setting, and higher than or equal to the Keep Alive Timeout setting.