Web Caching

Preface

When I first started using the Internet in 1986, my friends and I were obsessed with anonymous FTP servers. What a wonderful concept! We could download all sorts of interesting files, such as FAQs, source code, GIF images, and PC shareware. Of course, downloading could be slow, especially from the busy sites like the famous WSMR-SIMTEL20.ARMY.MIL archive.

In order to download files to my PC, I would first ftp them to my Unix account and then use Zmodem to transfer them to my PC through my 1200 bps modem. Usually, I deleted a file after downloading it, but there were certain files—like HOSTS.TXT and the “Anonymous FTP List”—that I kept on the Unix system. After a while, I had some scripts to automatically locate and retrieve a list of files for later download. Since our accounts had disk quotas, I had to carefully remove old, unused files and keep the useful ones. Also, I knew that if I had to delete a useful file, Mark, Mark, Ed, Jay, or Wim probably had a copy in their account.

Although I didn’t realize it at the time, I was caching the FTP files. My Unix account provided temporary storage for the files I was downloading. Frequently referenced files were kept as long as possible, subject to disk space limitations. Before retrieving a file from an FTP server, I often checked my friend’s “caches” to see if they already had what I was looking for.

Nowadays, the World Wide Web is where it’s at, and caching is here too. Caching makes the Web feel faster, especially for popular ...