Networking and Internet I-119
has access to a wide variety of services such as electronic mail, file transfer, vast information resources,
interest group membership, interactive collaboration, multimedia displays, real-time broadcasting,
shopping opportunities and much more. Some of the important services provided by the Internet are as
follows:
Electronic Mail (e-mail)
E-mail, is a fast, easy and inexpensive way to communicate with other Internet users around the
world. It is one of the basic and earliest services of the Internet and the most used application on the
Internet too. E-mail overcomes most of the problems and delays of getting a physical document from
one person to another. Rather, it has the dual advantage of not only being faster but cheaper to use
as well.
Each user of e-mail has a mailbox address to which messages are sent and the mailbox can be accessed
from anywhere and at anytime. It does not matter what type of connectivity the user is having, they will
always be able to use this service. One can receive and send e-mails from all systems whether it is a
Windows PC or a UNIX machine. Not only this, e-mail can also be used to send documents, images,
audio, video and so on as an attachment along with the mail.
File Transfer Protocol (FTP)
FTP is a set of rules that enables a user to log on to another computer and transfer information between
it and his/her computer. It was the first service developed for the Internet, so that government and
educational institutions could easily exchange files. FTP allows the user to get access to the files stored
in the directory of a remote computer that is connected to the Internet. Using FTP, one can upload and
download files from the remote computer (known as ‘FTP servers’), if they have access permission on
the remote machine. Though files can be transferred using e-mail, this is not a good choice if the file
size is large or when there are many files. FTP sites can consist of hundreds to thousands of files with
information on books, music, software, games, images, sounds, multimedia, course ware etc. FTP can
be done using the command prompt, browsers and various GUI-based FTP software programs such as
CuteFTP and WS_FTP.
Internet Relay Chat (IRC)
IRC is a service on the Internet that allows people to communicate in real-time and carry on conversa-
tions via the computer with one or more people. It provides the user with the facility to engage in simul-
taneous (synchronous) online ‘conversations’ with other users from anywhere in the world. Unlike other
forms of group communication on the Internet, chat is instant communication. However, both parties
must be connected to the Internet and that too at the same time, running the right software and actively
participating in order to chat.
Generally, the user runs a program (called ‘client’) to connect to an IRC server. The server relays
information to and from other servers on the same net. Popular IRC client applications are mIRC,
Virc and LeafChat. Once connected to an IRC server on an IRC network, the user will usually join
one or more ‘channels’ (also known as ‘chat rooms’) and converse with others there. Each channel
is devoted to a different topic. Conversations may be public (where everyone in a channel can see
what the user types) or private (messages between only two people, who may or may not be on the
same channel).
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I-120 Computer Fundamentals
13. Define the following terms:
(a) IP address
(b) HTTP
Ans: (a) Each system (computer or router) that connects to the Internet is assigned a specific Inter-
net address. This Internet address, referred to as ‘IP address’, uniquely identifies the connection of the
system to the Internet. Here, uniquely means that no two systems can be assigned the same IP address
at the same time. Moreover, IP addresses are universal that means each system wishing to connect to
Internet must accept the addressing system.
(b) HTTP (stands for ‘hypertext transfer protocol’) is the most common protocol that is used to
access information from the WWW. It manages the transfer of data between the client and the server.
The older version of HTTP was 1.0, in which TCP connection was released only after serving a sin-
gle request. This was not adequate as every time a new connection had to be established. This led to
the development of HTTP version 1.1 which supports ‘persistent connection’, that is, it is meant for
multiple request-response operations. HTTP is a stateless protocol and all the transactions between the
server and client are carried out in form of messages. The client sends a ‘request message’ to the server
and the server replies with a ‘response message’.
14. What is e-mail? Give its architecture.
(or)
With the help of an example, illustrate how e-mails are sent and received?
Ans: E-mail is the process of exchanging messages electronically via a communications network
using the computer. It allows users to communicate with each other in less time and at nominal cost as
compared to traditional phone or mail services. Apart from the textual message, e-mails can also consist
of other data formats such as pictures, sound and video. E-mails can be sent anywhere in the world using
the computer and a modem. Its delivery is almost instant and is very economical to use. One may send
many messages at a time or just one to a designated location.
The architecture of e-mail includes three components, namely, the user agent (UA), message transfer
agent (MTA) and message access agent (MAA). ‘UA’ is a program that helps the user in reading, writing,
replying and forwarding message. It also handles the user’s mailboxes. ‘MTA’ is a client/server program
where the MTA client can push messages to the MTA server. ‘MAA’ is a client/server program where
the MAA client pulls (retrieves) messages from the MAA server.
To understand how e-mail system works, consider two users A and B on two different systems.
Further assume that both A and B are connected to their respective mail servers by LAN or WAN. When
A wishes to send a message to B, it executes UA program to prepare the message. Now, as the message
is to be sent to A’s mail server through LAN/WAN, a pair of MTAs (MTA client and MTA server) is
used. The UA after preparing the message sends it to MTA client, which then sets up a connection with
MTA server on the mail server. At A’s mail server, the message waiting to be sent is kept in a queue
maintained by the mail server. Then, the mail server calls its MTA client to send the message to MTA
server at B’s mail server connected via Internet. At B’s mail server, the received message for B is kept
in his/her mailbox. To retrieve the message from mailbox at mail server, B calls the MAA client, which
then establishes a connection with MAA server at the mail server. This way B can receive the message
sent by A. Figure 6.9 depicts the whole mechanism.
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Networking and Internet I-121
15. Give some disadvantages of e-mail.
Ans: Though e-mail is quite popular and efficient, but it has got some disadvantages. These are as
follows:
• Although e-mail is delivered instantly, the recipient may or may not read their mail on time. That
defeats the quickness of electronic mailing.
• The slightest error in the address or a failure in one of the links between sender and receiver is
enough to prevent a delivery.
• Most webmails either display advertisements during use or append them to mails sent. It results in
increased size of the original mail, which brings a significant decrease in the speed of use.
• Since e-mail passes through network, it may be intercepted in between. Moreover, viruses can
enter the system while downloading the e-mails.
Multiple-choice Questions
1. Which of the following is not a valid topology?
(a) Bus (b) Ring
(c) Grid (d) Tree
2. In a network, all devices are connected to a device called hub and communicate through it.
(a) Bus (b) Ring
(c) Star (d) Mesh
UA
A
MTA
client
MTA
client
MAA
client
MAA
server
MTA
server
MTA
server
Internet
MessageMessage
B’s mail
box
B’s mail
server
A’s mail
server
Queue
B
UA
LAN/WAN
LAN/WAN
Figure 6.9 Mechanism of e-mail Transfer
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I-122 Computer Fundamentals
3. A is a computer network that covers only a small geographical area (usually within a
square mile or less) such as an office, home or building.
(a) LAN (b) WAN
(c) MAN (d) None of the above
4. Which of the following is not a network device?
(a) Hub (b) Bridge
(c) Router (d) USB
5. is a network device that connects two LANs or two segments of the same LAN.
(a) Router (b) Hub
(c) Switch (d) Bridge
6. Collection of related web pages is called .
(a) Web book (b) Website
(c) Web dictionary (d) Search engine
7. A is a program that accesses web pages and displays them on the computer screen.
(a) Browser (b) ISP
(c) URL (d) Home page
8. A telephone line is connected to the on the computer.
(a) USB (b) PS2
(c) Ethernet (d) Modem
9. Which of the following are the types of Internet access?
(a) Dial-up (b) Broadband
(c) DSL (d) All of the above
10. E-mail is the system for exchanging messages through .
(a) Client (b) Network
(c) Program (d) Backbone
Answers
1. (c) 2. (c) 3. (a) 4. (d) 5. (c) 6. (b) 7. (a) 8. (d) 9. (d) 10. (b)
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