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The Internet was developed to provide
a communication network that could continue to function in
wartime. Although the Internet has evolved in ways very different
from those imagined by its architects, it is still based on the
TCP/IP protocol suite. The design of TCP/IP is ideal for the
decentralized and robust network that is the Internet. Many
protocols used today were designed using the four-layer TCP/IP
model.
It is useful to know both the
TCP/IP and OSI networking models. Each model offers its own
structure for explaining how a network works but there is much
overlap between the two. Without an understanding of both, a
system administrator may not have sufficient insight into why a
network functions the way it does.
Any device on the Internet that
wants to communicate with other Internet devices must have a
unique identifier. The identifier is known as the IP address
because routers use a layer three protocol, the IP protocol, to
find the best route to that device. IPv4, the current version of
IP, was designed before there was a large demand for addresses.
Explosive growth of the Internet has threatened to deplete the
supply of IP addresses. Subnetting, Network Address Translation
(NAT) and private addressing are used to extend IP addressing
without exhausting the supply. Another version of IP known as IPv6
improves on the current version providing a much larger address
space, integrating or eliminating the methods used to work with
the shortcomings of IPv4.
In addition to the physical MAC
address, each computer needs a unique IP address, sometimes called
logical address, to be part of the Internet. There are several
methods of assigning an IP address to a device. Some devices
always have a static address, while others have a temporary
address assigned to them every time they connect to the network.
When a dynamically assigned IP address is needed, the device can
obtain it using several methods.
For efficient routing to occur
between devices, other issues must be resolved. For example,
duplicate IP addresses can stop efficient routing of data.
Students completing this module should be able to:
- Explain why the Internet was
developed and how TCP/IP fits the design of the Internet.
- List the four layers of the
TCP/IP model.
- Describe the functions of each
layer of the TCP/IP model.
- Compare the OSI model and the
TCP/IP model.
- Describe the function and
structure of IP addresses.
- Understand why subnetting is
necessary.
- Explain the difference between
public and private addressing.
- Understand the function of
reserved IP addresses.
- Explain the use of static and
dynamic addressing for a device.
- Understand how dynamic
addressing can be done using RARP, BootP and DHCP.
- Use ARP to obtain the MAC
address to send a packet to another device.
- Understand the issues related to
addressing between networks.
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