Every device, every computer, that is part of the Internet, is allocated
an address, called an Internet address, or Internet Protocol
address (IP address). The IP address is a series of numbers.
The mostly used protocol is called IPv4. Each IP address is actually
just four numbers each ranging from 0 to 255 (each of which
is called an “octet”) and separated by decimal points (called
dots). IP addresses are, therefore in the format xxx.xxx.xxx.xxx
where each xxx could be any number from 0 to 255. So an IP
address could look something like 161.184.138.36. This address
is essential during every exchange of data on the Internet,
because it identifies the client computer (which makes the
request, and to which the data must be sent) and the destination
computer (to which the request must reach). Nothing, therefore,
can happen on the Internet unless your computer is first
assigned an IP address.
Say you’ve specified the IP address of a Web site you wish to
access. A server usually has a static IP address. However, your home
PC, if you’re connecting to the Internet through a modem, is usually
assigned a different IP address by the ISP each time you dial
in. This IP address is unique to you as a user, but only for as long
as the session lasts. The reason for this system is that ISPs have to
deal with a large number of requests at the same time. Besides, at
any given time, the number of users of the ISP server is limited. To
assign permanent IP addresses to retail users wouldn’t really be
required; instead, ISPs simply allot any IP address that is not being
used at the time to each user who has just dialled in. This system
enables the ISP to get along with fewer IP addresses for the number
of users who are connected simultaneously.
TCP breaks down and reassembles packets of data. IP ensures
that the packets are sent to the right destination. The TCP/IP combination
is used because the Internet is a “packet-switched network.”
In a “circuit-switched network,” in contrast, once a connection
is made, that specific part of the network is exclusively used
only for that connection. In a packet-switched network, the connection
between the sender and the receiver is not single and
unbroken. When information is sent, it is broken into small packets
and sent over many different routes at the same time and then
put together in order at the other end once the packets of data
reach the destination.
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