 A network, in computing, is a group of two or
more devices that can communicate. In
practice, a network is comprised of a number
of different computer systems connected by
physical and/or wireless connections.

 A network of networks in which user of any
computer can get information from other
computers, if they have permission.
◦ An internet (note the lowercase letter) is two or more
networks that can communicate with each other.
◦ It is a generic term used to mean an interconnection of
networks.
◦ The second is the name of a specific world wide
network.
◦ The most notable internet is called INTERNET (uppercase
letter), in which connect more than hundreds of
thousands interconnected networks.
◦ a communications system that connects computers and
databases all over the world

 An intranet is an organization’s network,
that uses internet protocols, network
connectivity to securely share part of an
organization information or operation with its
employee.
 an intranet belonging to an organization ,
usually a company, accessible only by the
organization’s members, employees, or
others with authorization.

 An extranet is designed to connect the offices of
a large organization situated in metropolitan
area.
 Extranet is simply an external network.
 Intranet is accessible only to people who are
members of the same company or organization,
 An extranet provides various levels of
accessibility to outsiders like company with its
customers, suppliers, or other business partners.
 You can access an extranet only if you have a
valid username and password.
 Extranets are becoming a very popular means for
business partners to exchange information.

 An Internet service provider (ISP) is a company that
provides customers with Internet access. Data may
be transmitted using several technologies, including
DSL, cable modem, wireless.
 International ISPs: the international ISPs that connect
nations together example, Comcast, cox, centurylink
 National ISPs: The national ISPs are backbone
networks created and maintained by specialized
companies.
 Regional ISPs: The regional ISPs are smaller ISPs that
are connected to one or more national ISPs.
 Local ISPs: The local ISPs provide direct services to
the end users.

 ISP(internet service provider) list of Pakistan.
 ISP city Website
 Asia net Lahore www.asia.net.pk
 Brain net Karachi,lahore www.brain.net.pk
 Click online Peshawar www.click.net.pk
 Comsats Islamabad, www.comsats.net.pk
 Iqra Net Peshawar www.iqranet.net

 Every computer on the internet has a unique internet
address (similar to telephone number),
An Internet Protocol address (IP address) is a numerical
label assigned to each device connected to a computer
network that uses the Internet Protocol for communication
 Static IP addresses
◦ When a computer uses the same IP address every time it connects
to the network, it is known as a static IP address.
 Dynamic IP addresses
◦ In situations when the computer’s IP address changes frequently.
It is called a dynamic IP address.
◦ Don't tattoo your IP address to your arm, because it's not really
yours. Even at home it can change if you do something as simple
as turn your modem or router on and off. Or you can contact your
Internet service provider and they can change it for you.

 WWW
 The world wide web (commonly abbreviated as “the
web”) is a system of interlinked hypertext documents
accessed via the internet.
 The World Wide Web (WWW), also called the Web, is
an information space where documents and
other web resources are identified by Uniform
Resource Locators (URLs), interlinked
by hypertext links, and accessible via the Internet
 Introduced in 1990 by Tim Berners-lee
 Allows computer users to locate and view
multimedia-based documents
 It allows users to explore and retrieve text and
graphics from web sites.

 Web site
◦ A web site is a collection of web pages with some common
ownership.
◦ Like books web sites contain information and consist of
pages.
◦ A web site may consist of many pages or just a single page.
 Web page
◦ A world wide web page
◦ The individual pages that make up a web site.
◦ You can view a single web page at a time.
 Home page
 When accessing a web site, the first page displayed is usually
the home page. Often, like a book’s table of contents, it gives
information about what is available on that site.
 This is simply the first page displayed when you connect to the
internet, or , the starting point of your internet session.

 Application software that allows users to view web content
such as text, images, videos, music games and other
information located on a web page at a web site on the
www. Or
 A program on a computer that accepts requests for
information, processes the requests and allows you to
navigate to resources on the internet.
 Microsoft internet explorer
 Mozilla Firefox
 Google chrome
 Web browsers were introduced by companies like Mozilla,
Netscape, and Microsoft. More recently, Google entered
the browser market with Google chrome
 On the web, you navigate- commonly known as browsing
or surfing.

 Hyperlinks/ links
◦ One way to navigate the www is by clicking on a
link.
◦ A link is an area of a web page that , when you click
on it, will take you from the page you are presently
viewing to another page either within the same site
or to an entirely different site.
◦ Links can be anything on a page.
◦ Examples:
◦ Graphical or textual elements
◦ Underlined text: images, color varies but is often
blue, objects in motion etc.

 Uniform resource locator is a fancy term for the address
of a world wide web page or other resource.
 Used to identify web pages
 Example: https://www.vbs.com/welcome/main.html
 protocol Hostname File path
 The first part is protocol “:http://”
 Second is host name (domain name) or is the fully
qualified domain name.
 The term “domain name” usually refers only to the last
part of the host name, in this case “vbs.com” which has
been registered for that particular company’s exclusive
use.
 The third part of the URL “welcome/main.html” is the
path at which this particular web page is located on the
web server.

 DNS server translate symbolic name( such as
www.sharq.edu.af) into numerical IP address.
 Symbolic names are a great convenience because
they are easier to remember than numerical
addresses.
 For example, the domain name (www.example.com)
might translate to 198.105.232.4.
 It is like a phone book.
 DNS helps users to find their way around the internet.
 http://www.google.com here the domain name is
google.com
 The www is not necessary.

 The .edu is the top level domain-the top level
in which a site wants to register.
 The second level domain is typically the
company, organization or brand name for
most marketers.
 For example
 www.sharq .edu

 .com: it is used for commerical websites.
 .edu: it is used for educational websites eg
www.lums.edu.pk.
 .gov: Government institutions.
 .org: for organization.
 .mil: used for military websites eg
www.usa.mil
 .net Networking organizations, it represents
an organization that is working on network.
 .ca: used for canada.
 .th: used for Thailand.

 A communication protocol is set of rules that
control data communication.
 The protocol determine the following:
 How the sending device will indicate that it has
finished sending a message.
 How the receiving device will indicate that it has
received a message.
 A protocol defines what is communicated, how it is
communicated, and when it is communicated.

 https:// HyperText Transfer Protocol
◦ HTTPs is the protocol that supports communication
between web browsers and web servers.
◦ Hypertext Transfer Protocol Secure (HTTPS) is an extension
of the Hypertext Transfer Protocol (HTTP) for secure
communication over a computer network, and is widely
used on the Internet.
◦ https://www.google.com/results?search
◦ Protocol for client/server communication
◦ Very simple request/response protocol.
 Client sends request message
 Server replies with response message

 SMTP: Simple Mail Transfer Protocol
 FTP: File Transfer Protocol
 POP: Post Office Protocol
 SMTP is used to relay the mail messages to the
mail relay server. Hence it is used to transfer
the mail.
 FTP : "File Transfer Protocol." FTP is
a protocol designed for transferring files
over the Internet.
 POP is used to Download/Receive messages
from a mail server and store it locally on
computer.

 A server is a computer, a device that is
dedicated to managing network resources.
Servers are often referred to as dedicated
because they carry out hardly any other tasks
apart from their server tasks.
 There are a number of categories of servers,
including print servers, file servers, and
database servers.
 In theory, whenever computers share
resources with client machines they are
considered servers.

 Modulator-demodulator. Electronic device that allows
computers to communicate over telephone wires,
One computer's modem converts its digital signals
(which cannot be sent efficiently over phone lines)
into analog signals (which can be). The other
computer's modem reconverts the analog signals
(that the computer cannot understand) into digital
signals (that it can). Conversion of one type of signals
to another is called modulation, their reconversion to
the original type is called demodulation. Modern
modems work at 56 thousand bits per second or
higher data transfer speeds, perform automatic error
correction, and allow voice and fax communications.