Technical: More About Connectivity

Caching

One of the most effective techniques for improving computer and network performance is caching. If you visit a website, your browser can copy the text and images to your hard disk. If you visit the site again, the browser verifies that the stored copies are up-to-date, and - if so - the browser just displays the local copies.

Checking the date and time a file was last modified is a tiny request to send across the network - so small that modem throughput makes no difference. Latency is all that matters.

Recently, some companies have begun providing CD-ROMs of entire websites to speed Web browsing. When browsing these websites, all the Web browser does is check the modification date of each file it accesses to verify that CD-ROM copy is up-to-date. It must download from the Web only files that have changed since the CD-ROM was made. Since most large files on a website are images, and since images on a website change far less frequently than the HTML text files, in most cases little data has to transfer.

Once again, because the Web browser is primarily doing small, modification date queries to the Web server, latency determines performance and throughput is virtually irrelevant.

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