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icon <1K QuickestMirror 1.1

Last updated: March 3, 2001

Mac OS X Info

Due to radical changes in Mac OS X, this utility is now officially retired, that is, it will not be updated for Mac OS X. I might come up with minor updates, but only for previous releases of the Mac OS.

Download URL:


What's this?
How does it work?
How does QuickestMirror know the host list?
Will my favorite Internet app take advantage of the new URL scheme?
How do you pick a server?
Things that you won't find in the readme docs

Check out my TidBITS article: Mirror, Mirror on the Internet: QuickestMirror
Shareware Selection in the Internet Category on SHAREWARE.COM: "... we're so excited about QuickestMirror."
Power Downloader's Pick on DOWNLOAD.COM: "... will point you infallibly toward the fastest servers ..."
Reviewed on c't magazin für computertechnik (in German only).
QuickestMirror reviewed on TechWeb.
Was in The Mac Shareware Top 10.
Marco Piovanelli uses a QuickestMirror link with Style :-)
Check out Jeremy Roussak's Apollo.

What's this?


A new idea for the Internet. Technically speaking, a new Uniform Resource Locator (URL) scheme. Besides the specification for the fab URL scheme I am going to supply the first implementation, a "helper application" (tentatively dubbed QuickestMirror) for the new scheme.


Do you usually access information replicated on several Internet servers? If you are a Macintosh user, the answer is probably yes. Whether you are trying to download a program from the Info-Mac archives or to grab the latest stuff by Peter N Lewis, the information you are looking for is available on several servers.

How does it work?

When you try opening an URL like this:


QuickestMirror will show an ordinary list like the one shown below. The list is dynamically sorted so that the faster sites drift toward the top.

QuickestMirror list 3.5K

On Sunday, Nov 2, 1997 I read this on MacInTouch:

The freeware Eudora Light 3.1.3, a new version, is posted on a download page, but we had problems with the FTP server this morning.

Here is where QuickestMirror comes useful. Just try fab://ftp.eudora.com/eudora?eudoralight/mac/english/3.1.3/ to witness.

How does QuickestMirror know the host list?

These lists are stored locally, inside QuickestMirror itself. For this reason, if you know of distributed resources worth including please let me know.

It is certainly possible to devise a protocol allowing to retrieve such lists dynamically. Interested parties may want to know about spoofing attacks first.

Will my favorite Internet app take advantage of the new URL scheme?

Well-behaved Macintosh applications handle URL-related actions through InternetConfig. These applications will transparently use the new URL scheme, provided that you tell InternetConfig that the helper for the fab scheme is QuickestMirror itself.

There are notable exceptions, of course, such as Netscape: the popular browser requires an AppleScript kludge like this:

tell application "Netscape Navigator"
register protocol "QMir" for protocol "fab"
end tell

This instructs Netscape to let QuickestMirror handle fab URLs. In theory you should run this script only once, but...

I've just learned that Netscape Navigator, versions 3.0 through 3.0.2, sometimes cannot retain what protocols have been registered. More information about this can be found at the Netscape Preferences Fix home page. You can download the fix itself from the Info-Mac archives, just 9K.

How do you pick a server?

Although you are really concerned about network performance, most people often recommend "choose the mirror nearest to you". This is not a sound recommendation, because empirical evidence and scientific inquiry show clearly that geographical nearness is not a valid indicator for network efficiency.

This and other important results are found in this most interesting paper by Mark E. Crovella and Robert L. Carter, which I found almost by chance with Alta Vista.

Since a complete understanding of this paper requires a background in maths and statistics, I summarize here their findings (these sentences have more or less been excerpted from the paper):


QuickestMirror requires InternetConfig (possibly 1.1 or later, although 1.4 or later is recommended). It requires Open Transport 1.1.1 or later to assess network performance; MacTCP users can still pick a server at random, which is better than a fixed selection.

QuickestMirror ships as a "fat binary" application and requires a 68020 processor. If there is demand, I will build a 68000 version for separate distribution.

Things that you won't find in the readme docs

This page was last built with Frontier on a Macintosh on Mon, Apr 22, 2002 at 9:41:26 PM by
Fabrizio Oddone, fab@kagi.com