Find Closest Download Mirror

This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. It does not describe an actual complete program. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; I have too many other projects of my own.

I do contract work for a living, which could include writing a program such as this. However, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project any way you please.

The Problem

When you go to download a program in your browser, it often presents you with a list of twenty or so mirror sites you could download it from. Which should you choose? This program automatically selects the best one and downloads the file for you.

Factors Considered

How would software decide which download site was best?

Protocol message to reveal approx latitude/logitude of servers. This is used to narrow down the list to the most likely candidates.
a small test download.
remembering the results of previous small test downloads.
a message from the server indicating how busy it is just now. This can be used to adjust the effective rates from previous small tests to avoid repeating the small test every time. This also acts to inform users of servers that are down.
Geographic IP analysis to guess the approximatet locations of users.
Users tell you their latituted and longitude.
GPS interface so the user location information can be done automatically.

How it Works

The user copies the webpage containing the list of mirrors to the clipboard and pastes it into the downloader program. You just click Download with material in your clipboard. The downloader parses the page to extract useful information. To start, just handle the Simtel format list of mirrors. Often the countries of the various mirrors are available. You know the user’s country from the user.country system property.

Perhaps you can guess an approximate location of the mirror from DNS lookup or the IP.

This gives you a short list of candidates. You then try downloading say 20K of the file from each mirror and see which responds fastest. (If the file is short, you just pick a random mirror. It is just a waste of time optimising.) This will pick a close, lightly loaded mirror. This will also exclude mirrors that are down.

Extract the filename from the webpage also. Then download the file to the predesignated target directory in the background, showing a progress bar if the user is curious.

Getting Fancy

Make the downloader multi-thread so that it can queue up requests and do several at once. It determines by experiment how many at once is optimal. If it gets a disconnect or the system crashes, it does its best to pick up where it left off, perhaps completely restarting the downloads’ in progress. It may even restart the download from a different mirror.

Building It In

If some large mirror site like SourceForge or Apache Jakarta could be persuaded to adopt a server protocol for determining optimum mirror, then the entire download process could be completely automated with an Applet. It could even pick up with an alternate mirror in midlight if one failed. From there the use of the protocol could spread to become the standard for all mirrored downloads.

IP tracer

	Please email your feedback for publication, errors, omissions, broken/redirected link reports and suggestions to improve this page to Roedy Green :
	Canadian Mind Products
	mindprod.com IP:[65.110.21.43]
	Your face IP:[38.103.63.17]	The information on this page is for non-military use only.
	You are visitor number 954.	Military use includes use by defence contractors.
	You can get a fresh copy of this page from:	or possibly from your local J: drive (Java virtual drive/Mindprod website mirror)
	http://mindprod.com/project/closest.html	J:\mindprod\project\closest.html