TCP IP NETWORKING

TCP/IP
By far the most common way to connect your UNIX box to a network
is with ethernet and TCP/IP. While other networking schemes will
work and are often used, your system will practically always start off
with these two. TCP/IP stands for Transmission Control Protocol/Internet
Protocol. The name refers to the two layers of the networking protocol
that are used and are discussed very well in many books about the
Internet and networking. The Internet is a TCP/IP-based network, so
an understanding of networking will help you to better understand
how your system will work on the Internet. The standard version of
TCP/IP is called IPv4. There is a newer version of TCP/IP that allows for
many more hosts

NETWORK CLASSES
TCP/IP networks are broken up into three classes in order to set the maximum
number of hosts per network and the maximum number of networks.
The value used for WWW (the first group of three numbers) will
determine its network class. The classes will differ in the number of possible
networks and the number of hosts per network. In Table 1.1, the values
for XXX, YYY, and ZZZ will vary from 1 to 254. The table summarizes
the features of the various classes of networks.
The remaining values for XXX, ranging from 224 to 254, are used for special
types of networks. You will note that the XXX value of 127 is not
listed in Table 1.1. This is a special address called the loopback or local address;
it is used by the host to connect to itself and can be used even if
you have not set up a Network Interface Interface Card (NIC). The only address
that is used in this range is 127.0.0.1.