Friday, March 21st, 2008

Roundup on Parallel Connections

Category: Browsers, Performance

Steve Souders has taken a step back, analyzed the blog content that came out of IE 8 supporting 6 connections per host, and has pulled together the facts to discuss:


Section 8.1.4 of the HTTP/1.1 RFC says a “single-user client SHOULD NOT maintain more than 2 connections with any server or proxy.” The key here is the word “should.” Web clients don’t have to follow this guideline. IE8 isn’t the first to exceed this guideline. Opera and Safari hold that honor supporting 4 connections per server.

Settings for current browsers

Steve documents the browsers, and discusses how you can tweak the settings in your own: “It’s possible to reconfigure your browser to use different limits. discussion about increasing Firefox’s number of connections. In comment #22 Boris Zbarsky lays out a good argument for why this increase will have no effect on most servers. But in comment #23 Mike Hommey points out that persistent connections are kept open for longer than the life of the page request. This last point scares me. As someone who has spent many hours configuring Apache to find the right number of child processes across banks of servers, I’m not sure what impact this will have.

Having said that, I’m please that IE8 has taken this step and I’d be even happier if Firefox followed suit. This change in the client will improve page load times from the user’s perspective. It does put the onus on backend developers to watch closely as IE8 adoption grows to see if it affects their capacity planning. But I’ve always believed that part of the responsibility and joy of being a developer is doing extra work on my side that can improve the experience for thousands or millions of users. This is another opportunity to do just that.

Posted by Dion Almaer at 10:10 am
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3.3 rating from 10 votes

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For most applications that don’t have millions of users, like internal business applications, the two connection limit usually just means the developer has to make three hosts pointing at the same IP so I for one welcome our new six connection overlords.

Comment by davejohnson — March 25, 2008

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