How Does it Work?
When we pick up the phone to make a call, a dedicated connection between our
phone and the other phone is made. This type of dedicated connection is called
circuit-switched. All communication between the two stations
uses the established dedicated connection. Network connections rely on another
type of connection: packet-switched. Compared to
circuit-switched, there is no dedicated connection between the two systems. The
information stream is chopped into small pieces (packets) that are placed onto
the network by the network hardware of the source system. It is the
responsibility of other network hardware to deliver that packet to the
destination using the address of the destination system that is contained in
each packet. Once the destination receives the packets, they must be
re-assembled into the original information stream. The network hardware only
knows where to deliver the packet and need not know what the route is the packet
will be traveling.
How then does the network know where to send the packet? The answer to this
question is: every computer system that is on the Internet has a unique address
referred to as the Internet address or IP number.
(Please note that this is NOT
your E-Mail address.) This unique address is a 32-bit number, but to make it
more readable for us humans it is commonly written as four numbers separated by
periods also called the dotted decimal notation. Internet address written in
the dotted decimal notation When you want to connect your computer to the
Internet you must obtain such a unique address. If you wish to communicate with
another computer over the Internet, you need to know the other system's IP
number. We humans are better at remembering names rather than numbers and,
therefore, each computer on the Internet can also be given a name. However,
since the computer really uses the IP number, the corresponding IP address needs
to be found for each name, similar to the way we use a telephone book.
The TCP/IP family of protocols defines the standard of how to communicate
among the interconnected networks of the Internet. This set of rules allows
systems from various manufacturers, running different computer software on
incompatible hardware to exchange information, provide the TCP/IP standards were
followed. These standards define how the packets look, how computers set up a
connection to exchange data, what to do in case of errors, and so on. The
versatility of the TCP/IP protocol was illustrated in 1978 when a dumb terminal
located in a mobile van driving along a California highway made a connection to
a computer located in London, England. Modern computer networks are comprised
of powerful personal computers instead of dumb terminals, but the basic TCP/IP
services: file transfer (the File Transport Protocol FTP), remote access to a
host computer (Telnet), and electronic mail (E-MAIL), are very much an essential
part of any TCP/IP implementation.
