connections— brief communication sessions
between two machines — that it can handle in
a given period of time. The number of connections
that the server handles depends on how
quickly the server establishes a connection,
deciphers the request, sends the requested file,
and terminates the connection. Most people
assume that the most time-consuming step in
this process is the speed with which files are
transmitted. Surprise! When small files are
transmitted, the bottleneck is usually not how
fast the files are transmitted, but how quickly
the server’s hardware and software establish
connections for each of the file transfers, and
how fast the connections are terminated after
the transfer is finished.
Engineers and various hangers-on, such as
people who write computer-related books, like to
call the cause of a bottleneck a gating factor.For
example, the gating factor for completing this
book on schedule is the speed at which the
authors write. The gating factor in serving simple
Web pages is often the speed with which the
server can connect and disconnect, not the
speed with which data can be sent over the wire.
In addition to the speed of connecting and disconnecting
to other machines, the speed of the
server’s connection to the Internet makes a big
difference, especially for larger files such as
big graphic images. If you have a direct connection
to the Internet (as you find at most large
companies and most universities, your clientside
connection may be even faster than the
server’s connection: Lots of personal and small
business home pages are sitting on Web
servers with nothing but a 56 Kbps modem connecting
them to the Internet. So don’t start
cussing at your own modem when that full-color
JPEG photograph of the winning Weimaraner
takes forever to download; the problem may be
at the other end.