Speeding Up FireFox When Using the ASP.NET Development Server from Localhost

Ref: http://scottonwriting.net/sowblog/posts/13367.aspx

I have long used FireFox as my default browser for surfing the web,
but I typically test my ASP.NET pages on Internet Explorer for a couple
of reasons:

• Some of the larger software projects I work on are developing
  intranet applications, where all users' browsers are fixed (IE 6 for
  one client, IE 7 for another).
• For book and article and tutorial screen shots I typically use IE
  as my browser of choice because IE is still, after all, the most used
  browser.
• Until Visual Studio 2008, Visual Studio used IE as the browser when
  debugging an ASP.NET application (even if FF was setup as the default).
  Because all of my clients are still on ASP.NET 1.x or 2.0, I don't use
  VS 2008 too often.

However, I have recently been working on some AJAX material and have
been using VS 2008 more frequently. Visual Studio 2008 kindly launches
my default browser (Firefox) when I debug my web application. The
problem was I noticed that Firefox was loading pages very slowly. I'd visit a site through localhost (via the ASP.NET Development Web Server) and pages would take several seconds to load.

To help analyze the problem I used the excellent Firefox extension Firebug (which I reviewed in the March 2008 issue of my Toolbox column). Firebug
will show you the total number of network resources downloaded when
visiting a page, along with the time it took to download each.

Each resource - from the 4KB HTML fiel to the 7KB JPG file, was
taking close to a FULL second to retrieve! When requesting this same
page from a remote, production web server, download times were 5 to 10
times faster per resource. What was going on here?

I next opened Internet Explorer - the same pages loaded instantaneously. I fired up Fiddler,
an excellent HTTP Debugger for IE, and noted that the resources were
being downloaded in 0.02 seconds, nearly 500 times faster than from
Firefox. By now I was seriously stumped. I then did what I should have
done from the getgo - I searched the web. Duh!

Turns out that there is a known issue with Firefox's IPv6 support
and the ASP.NET Web Development Server that introduces these lengthy
delays. To quote from the Mozilla Wiki:

IPv6 was designed in part to solve the problem IPv4 will soon be
facing: the exhaustion of all possible IP addresses. Mozilla
implemented IPv6 support in early 2000, but that support did not
receive widespread testing until recently as IPv6-capable OSs and
network software/equipment became more common. One particular bug that
has appeared exists not in Mozilla, but in IPv6-capable DNS servers: an
IPv4 address may be returned when an IPv6 address is requested. It is
possible for Mozilla to recover from this misinformation, but a
significant delay is introduced.

...

Two approaches were taken to work around these bugs: first, a
preference to globally disable IPv6-based DNS lookups browser-wide
(this preference [network.dns.disableIPv6]), and a blacklist of domains which should never have IPv6-based DNS lookups performed (network.dns.ipv4OnlyDomains).

Consequently, to fix this problem of slow response times when
visiting localhost using Firefox, either set the network.dns.diableIPv6
configuration property to true or set the network.dns.ipv4OnlyDomains configuration property to “localhost”. My search led me to many pages around the Web suggested that you set the nework.dns.disableIPv6 property to true, but this would disable IPv6 support for all sites visited by the browser (at least according to the Wiki documentation). Therefore I set the network.dns.ipv4OnlyDomains property to “localhost”.

To set these properties, fire up Firefox and type about:config
in the address bar. Next, locate the appropriate setting and change its
value to the desired one. With that small change the debug-time
experience in Firefox is greatly enhanced. And make no mistake,
Firefox's rich library of extensions make it a great browser for web
development. (I'll share some of my favorite Firefox web development
extensions in a future blog post.)

Lesson for the day: If you bump up to a problem, search for a solution online first.
If your search is fruitless then take the time to investigate it
further, otherwise you may spend 15 minutes troubleshooting a problem
that is already well-known and has a simple solution.

posted on Wednesday, July 09, 2008 1:54 PM