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