Information Technology Reference
In-Depth Information
IP Number: An Internet Protocol (IP) number is a 32bit address
that often is written as a fourpart decimal number. You usually do
not type this part of the Internet address when searching for a site,
although you could. Rather, the domain name you do type in corre
sponds to a central computer that has a specific IP number, and this
number is communicated to your computer by a server. For exam
ple, cs.utexas.edu corresponds to 128.83.139.9, so when you type
in “
http://www.cs.utexas.edu,
” your computer consults a server
that identifies this address as corresponding to the IP number
128.83.139.9. This allows your computer to contact the central
computer named cs.utexas.edu.
IP numbers also are arranged hierarchically. For example, con
sider the IP numbers corresponding to Grinnell College, as shown
in Figure 11.1. All of Grinnell's addresses begin with 132.161. . . ,
and the machines related to academic computing begin 132.161.10
. . . . The machines related to the Grinnell's mathematics and com
puter science departments are divided into three subnetworks with
IP numbers 132.161.31 ..., 132.161.32 . . . , and 132.161.33 . . . .
As with domain numbers, IP numbers are defined so that no two
correspond to the same location or machine.
.edu
edu domain
grinnell.edu
132.161. ...
Grinnell College
Subnetworks for the
Department of Mathematics
and Computer Science
at Grinnell College
132.161.31. ...
132.161.32. ...
132.161.33. ...
duerer.cs.grinnell.edu
(printer)
132.161.33.145
Individual machines
Figure 11.1
The IP number hierarchy for computers at Grinnell College.
