What is the relationship between IIS settings HTTP Keep-Alives Enabled and Connection Timeout?

Question

What is the relationship between IIS settings HTTP Keep-Alives Enabled and Connection Timeout ? Is it the same relationship in different versions of IIS?

I am using XP Pro (2002 service pack 3) using IIS 5.1 running aspnet 3.5 applications.

We have been getting 'There are too many people accessing the Web site at this time' error.

I am reducing the connection timeout from 900 to 60 seconds. What additional effect would unchecking HTTP Keep-Alives Enabled have?

We plan to upgrade the webserver from the XP Pro to another machine.

Answer 1

Unchecking HTTP Keep-Alives would probably increase the number of connections made to the server.

Without HTTP Keep-Alives each element on a page (for example images) would require a separate connection to the server. HTTP Keep-Alives enabled will allow an existing connection to be reused.

There's a very good article about this here:

Enabling HTTP Keep-Alives to Keep Connections Open (IIS 6.0)

Although it says it's for IIS6, it applies equally to IIS5.1.

Answer 2

First using Windows XP as a "server" itself is a horrible thing. XP is a client side Windows which has limitation on concurrent connections. I believe that's why 'There are too many people accessing the Web site at this time' happens.

If you disable HTTP Keep-Alives, then it may improve a little bit as concurrent connections may drop under a few scenarios (it may not improve if you really have a lot of users). But if you really care about the users of your web applications, consider Windows Server products.

Answer 3

If you disable the Keep-Alives Visual Studio doesn't automatically attach to the browser process to debug web applications.

I've found that reducing the Connection Timeout to 65 seconds seems to stop the "Too many people are accessing your website" problem.

There's a method outlined here to increase your connection limit from 10 to 40 connections.

Update: I've made this post a community wiki so people can change the Connection Timeout by trial and error until we find the best value for it.