Using the Network Interface
An Overview of TCP/IP Networking and the Internet
8-6
SPARCbook Portable Workstation User Guide
The majority of smaller organizations use class C addresses, which
provide 254 possible host addresses on their network. By convention,
host address 0 is used to represent the network itself and 255 is used as
a broadcast address. A message sent as a broadcast on a network is
received by every other host attached to that network.
In addition, address 127.0.0.1 is used as a loopback address; data sent
to this address is transmitted back to the same host for testing. This
address is usually given the hostname localhost in the
/etc/hosts
file
(described later in this chapter).
Addresses used by systems not connected to the Internet
By convention, sites that are not connected to the Internet use 192 or
193 as part
a
of their network address. However, even if you do not
intend to access the Internet immediately, you are advised to obtain an
official Internet address for your site. See “Registering Internet
Network names
Although IP addresses provide computers with an efficient means of
identifying the source and destination of data and messages transmitted
across the Internet, it is much more intuitive for humans to use names.
TCP/IP provides a flexible naming system which allows this.
The global Internet is organized into a hierarchical structure of domains
that follow the network’s organizational and geographical structure. At
the top level, or root domain, the Internet is organized into a number of
domains which reflect the type of organizations or geographical
territories within them. For example,
.com
identifies a domain used by
commercial organizations most often in the United States. There also
exist codes for individual countries such as
.uk
for the United Kingdom
or
.fr
for France.
Commercial companies, educational establishments and government
departments can access the Internet within these domains either directly
or through an access provider. The Internet address for an organization
consists of a name which is unique to that organization.
S3UG4_Book Page 6 Friday, August 8, 1997 11:37 am
