Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

There is a limit on connections somewhere along the line here... On a windows server 2008 machine, each request to a url running on localhost takes ~3 seconds to complete. This is fine and normal for the url.

However, if i open the same localhost url in about 10 tabs, and set them to reload all at the same time, they finish sequentially, 3 seconds after each other. Meaning the last tab has taken 30 seconds to load (3s x 10). What is especially odd is that firebug reports each page as taking 3seconds to load. Another point to add is that the status bar just sits at 'done' for the last tab until 3 seconds before completing, where it then changes to 'waiting for localhost'.

I am praying there is some connection limit somewhere otherwise this would be a disaster if more than one user ever visited the site at a time! Maybe a limit or something where one pc cant make more than 2 simultaneous requests to a url at a given time?

share|improve this question

Firefox defaults to allowing 15 connections per server with a maximum of 6 persistent connections, any subsequent connection has to wait. You can change these by editing network.http.max-connections-per-server and network.http.max-persistent-connections-per-server in about:config .

For IE (and earlier) the default limit used to be 4. IE8 has a somewhat dynamic behavior but generally allows up to 8 connections. There's a Microsoft KB article on the change here.

Chrome has a limit of 6.

In your testing it seems as if you are running into this limit but there are some other settings like network.http.pipelining that may help you get a more representative behavior for testing. Ideally though you should look at some proper web server load testing apps for this.

share|improve this answer

By default, IE7 allows two connections at a time, IE8 six. You can change this as described in the following article:

More information here:

Connectivity Enhancements in Internet Explorer 8

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.