Lecture 1: Introduction to computer ■ Coworkers discussing each other’s work, or

collaboration, assisted the widespread use of

networks computers.
Identify Human and Computer Networks
■ Networks help centralize the management of
■ A network consists of two or more entities software and maintenance of computers, such as
sharing resources and information. installing upgrades and backing up data.
■Examples of basic networks include your human
network, school lunchrooms, restaurant dining, Distinguish Between the Different Types
and business contact development.
of Networks
■ The capability to share is enhanced when ■ Networks are frequently classified according to
information is stored on computers. the geographical boundaries spanned.

■ Computer networks consist of two or more ■ A network contained within a relatively small
computers that are connected and able to area, such as a classroom, school, or single
communicate. building, is commonly referred to as a local area
network.
■ Networked computers share resources and
information. ■A network that spans the distance of a typical
metropolitan area is sometimes referred to as a
■ Powerful networks result when additional metropolitan area network.
computers are added to the communication
possibilities. ■ A network covering a larger area than a single
city is classified as a wide area network
■As more and more data become available over a
network, some kind of a control system must be ■Another method used to classify networks
established. focuses on which computer controls the
network’s operation.
■The hierarchy of data should be used in network
planning. ■All computers on a peer-to-peer network can be
considered equal.
■Access to data stored higher up in this chain is
more strictly controlled, which means fewer ■ Peer-to-peer networks are popular as home
people can view that data. networks and for use in small companies because
they are inexpensive and easy to install.
■ Data is defined as a piece or pieces of
information. ■Server-based networks offer central control and
are designed for secured operations
■ The collection, proper manipulation, and
effective tracking of data makes information ■ A dedicated server operates solely as a server
management on networks so important. by storing data, applications, and other
resources, and providing access to those
Describe the Benefits of Networks resources when called for by a client.
■Computers operated independently from others ■ Client-based network servers process requests
are known as stand-alone computers. from clients and return just the results.
■ Sneakernet was the term used for running data ■ Client-based networks take advantage of their
from one computer to another on disk. own powerful processors as well as the
increasingly powerful computers used as typical
■ Most computer networks develop to facilitate
workstations.
communication, initially to share output and later
to communicate through e-mail.

■The ability to share resources is another main

purpose for initiating networks.

■ Peripherals are additional components that

attach to computers to expand their use.

■ Sharing peripherals, such as printers, often

offered enough of a cost savings for companies to
invest in networks.

■ Large computers can be set up as storage

locations where data is offloaded and access to it
is controlled by the person storing the data.

■ Installing an application on a network and then

sharing its use cuts down on the storage space Lesson 2: Different types of devices used to
required when multiple users need the same create a computer network
application.
Client is the term used to mention a workstation, A router is another type of network connectivity
a normal desktop computer, or a laptop which an device. Routers operate at Layer 3 of OSI
end user uses to perform his normal duties in the reference model. A router is used to forward and
office. The term client computer is used to refer receive traffic between different Layer 3 network
any device which participate in the network. segments. Routers depend on IP addresses (also
called as Layer 3 address) to forward traffic from
Workstation is the term used for a high-end type one network to another network. That means,
computer which has much more memory and switches are used to connect devices inside a
processing power than a normal desktop Layer 3 network segment but routers are used to
computer. Workstation computers are used for connect different Layer 3 network segments
computing tasks which require more memory and together.
processing power than normal computing.
Examples are video rendering, 2D CAD drafting, A firewall is a network security device which is
3D CAD drafting, heavy image editing etc. used to prevent unauthorized traffic. Firewall can
inspect, control, police and if required block
Server is a high configuration special computer, network traffic. Firewall can be a software, a
which serves resources to clients. A typical hardware device or a software running on a
computer network uses different types of servers. special hardware device. Typically, firewalls are
Examples of servers used in a network are file used to prevent unauthorized access to private
server, print server, database server, mail server, networks from the users of internet.
web server, DNS server, DHCP server, video
streaming server etc. Servers normally run An intrusion prevention system (IPS) another
continuously 24/7. An unexpected shutdown of a network security device which is used to detect
server may cause entire operation of the and prevent network threats. Intrusion prevention
business down. systems (IPS) can be connected inline within your
network and it can continuously monitor your
Network media is used to connect different network for any network threats. These devices
devices in a network together. Commonly used can identify traffic patterns of different network
network media in wired networks are copper threats. Intrusion Prevention Systems (IPS) can
twisted pair cables. Optical fiber cables are also report any threat to the network administrator or
used to connect different devices in wired it can proactively shut the line, if a threat is
networks. Wireless networks use electromagnetic identified.
waves to connect different devices together.

Network hub (Ethernet hub) is a network

connectivity device used to connect clients during
the early days of computer networking. A network
hub receives traffic from a device in the port
where the device is connected. Ethernet hub then
forwards the received traffic out to all its other
ports. As a result, all the clients in the network
receive the traffic which is a burden to other
clients which are not the intended recipient. This
nature of operation of Ethernet hubs can cause
large amount of unnecessary traffic in the
network. Hubs are out from the computer
networking industry and not even available in the
market to purchase.

Switch A layer 2 switch is another type of

connectivity device widely used these days. Layer
2 switches operate at Layer 2 of OSI reference
model. A network switch has the capability to
learn which devices are connected to its ports.
Switches learn about connected devices by using
a unique device address called as Media Access
Control (MAC) address or Layer 2 address. Using
Media Access Control (MAC) address or Layer 2
addresses, a Layer 2 switch can forward the
packet only to the intended recipient, not to
every device in the network. A network switch is
commonly used to connect the devices inside a
OSI Layer 3 network segment.

Access Points (AP) are used in wireless networks.

Access Points (AP) are used to connect wirelessly Lecture 3: Client and Server Architecture
connected devices to wired network. Typically
Access Points (AP) is a separate device, but it can Client Computer. You can think a client as a
be a function of router also. computer in your network, where a network user
is performing some network activity. For
Example: Downloading a file from a File Server,
Browsing Intranet/Internet etc. The network user Client Operating System
normally uses a client computer to perform his
day to day work. Client Operating Systems (Workstation Operating
Systems, or Desktop Operating Systems)
What is a Server Computer? The client
computer establishes a connection to a Server Windows 95/98/ME Vista (obsolete)
computer and accesses the services installed on Windows NT Workstation / Windows 2000
the Server Computer. A Server is not meant for a Professional (obsolete)
network user to browse the internet or do
spreadsheet work. A Server computer is installed  Windows XP (obsolete)
with appropriate Operating System and related  Windows 7 (obsolete)
Software to serve the network clients with one or  Windows 8 / Windows 8.1 (obsolete)
more services, continuously without a break 24/7.  Windows 10 Desktop (Current)
An Operating System (also known as "OS") is the  Red Hat Enterprise Linux Workstation
most important set of software programs which  SUSE Linux Enterprise Desktop
are loaded initially into any computer-like device  Ubuntu Desktop
by a bootstrap program. Operating System  LinuxMint
controls almost all the resources in a computer,  Fedora Workstation
including networks, data storage, user & user
 elementary OS
password database, peripheral devices etc.

Operating System Software products are so

complex software products. Operating System
Software products are compiled from millions of
lines of source code. Operating system products
we have currently are created by the hard work
of thousands of engineers for decades, internally
in a company (Example: Windows) or by
dedicated global volunteer communities
(Example: GNU/Linux, BSD Unix).

A Network Server computer offers its services to

a group of Network Client devices. A Server
computer typically has more computing
resources like Processors & Processing Power,
more Physical Memory (RAM), more Storage
Space etc., compared to client computers. The
Server computer machine runs on Server
Operating System, also called as Network
Operating System (NOS), which normally has
more features and processing capabilities
compared with the client computer's Operating
System. The server may be installed with special
software, to function as a Server Role. The special
software allows a Server Computer to function a
particular server role, like a File Server, Web
Server, Mail Server, Directory Server etc.

A Network Operating System (NOS) includes

much more capabilities than a normal client
workstation (or Desktop) Operating System. Most
popular Network Operating Systems are listed
below.

• Microsoft Windows Server 2012

• Microsoft Windows Server 2016 Lecture 4: Common network Applications

• Microsoft Windows Server 2019 Web Browser: A web browser is a network
(Current) application which enables the users to access the
internet. Web browser interprets HTML
(HyperText Mark-up language) files sent from a
 Unix (Oracle Solaris, IBM AIX, HP UX, Web Server and displays the content in its
FreeBSD, NetBSD, OpenBSD, Xinuos screen. Web Browser is the most widely used
Open Server/SCO Unix etc) network applications.
 GNU/Linux (RedHat Enterprise Linux, Most widely used Web Browser products are
Debian Linux, SUSE Linux Enterprise
Server, Ubuntu Server, CentOS Server, • Mozilla Firefox Browser
Fedora Server etc. • Google Chrome Browser
• Microsoft Edge Browser Summary
• Opera
 Everyone has access to the Internet.
E-mail Applications: E-mail (Electronic Mail)
Applications are used for composing and sending  People who work for a company will have
e-mails within the same network or to outside the access to the company intranet.
network.  An extranet is created by a company to
Most widely used E-mail (Electronic Mail) offer customers, suppliers and vendors
Applications products are specific data without allowing them access
to other proprietary or sensitive company
• Mozilla Thunderbird data.
• Microsoft Office Outlook
• Evolution

Instant Messaging Chat Applications: Instant

Messaging Chat Applications are used these days
for corporate communication and for general
chat.

Most widely used Instant Messaging Chat

Applications products are

• Apache OpenMeetings
• Microsoft Skype
• WhatsApp Messenger
• Cisco WebEx

Collaboration Applications: Collaboration

network applications are mainly used inside a
company for a group of employees to work
together for a common task. Collaboration
network applications allow employees to transfer
their files to a central storage repository and work
together on it.

• Microsoft SharePoint
• Zoho Connect
• Oracle Beehive
• Google G Suite

Lecture 5: Internet, Intranet and Extranet

The Internet is a global wide area network that

connects computer systems across the world. It
includes several high-bandwidth data lines that
comprise the Internet "backbone." These lines are
connected to major Internet hubs that distribute
data to other locations, such as web servers and
ISPs.

Lecture 6: Network Protocols

A network protocol can be viewed as a common

An intranet is a private network that can only be network communication standard, which is used
accessed by authorized users. The prefix "intra" to define a method of exchanging data over a
means "internal" and therefore implies an computer network. Network protocols define rules
intranet is designed for internal communications. and conventions for communication between
"Inter" (as in Internet) means "between" or different devices, participating in a computer
"among." Since there is only one Internet, the network.
word "Internet" is capitalized. Because many A simple real-world example is human
intranets exist around the world, the word communication. Let us assume that you are a
"intranet" is lowercase. native English speaker and the only language you
An extranet actually combines both the Internet know is English. If you try to speak to someone
and an intranet. It extends an intranet, or internal over the phone who can speak only Hindi
network, to other users over the Internet. Most language, the communication will miserably fail.
extranets can be accessed via a Web interface Here for communication between two parties
using a Web browser. (without the help of a translator), you must need
a common language which both parties can Two terms are often used in networking industry,
understand and speak. when describing about network protocols.

Similar to above example, if computers (or 1) Proprietary Protocol 2) Standard Protocol

computer like devices) want to communicate
each other, they must follow certain set of Proprietary protocols are usually developed by a
predefined communication rules. A network single company for the devices (or Operating
protocol is that set of rules that should be System) which they manufacture. AppleTalk is a
followed by different computers or computer-like proprietary network protocol developed by Apple
devices when they participate in network Inc. Appletalk protocol is an excellent protocol
communication. and Appletalk protocol work well in network
environments made of Apple devices. But other
Almost all protocols used in the Internet are Operating System software vendors may not
common standards defined by RFC (Request for support Appletalk protocol. Proprietary protocols
Comments). will not scale well in network environments
consisting of multi-vendor Operating System
software products or network devices.
Examples of standard network protocols are TCP
(Transmission Control Protocol), UDP (User
Datagram Protocol), IP (Internet Protocol), ARP Standard protocols are agreed and accepted by
(Address Resolution Protocol), HTTP (Hypertext the whole computing industry. Standard protocols
Transfer Protocol), FTP (File Transfer Protocol), are not vendor specific. Standard protocols are
TFTP (Trivial File Transfer Protocol), SMTP (Simple often developed by collaborative effort of experts
Mail Transfer Protocol), SSH (Secure Shell), Telnet from different organizations.
etc.

Devices participating in network communication

should know about the common network protocol
and communicate according to the way, defined
by the network protocol. In other words, standard
network protocol software must be running on
both devices participating in network
communication.

Following example explains it more clearly.

If you are using your browser to browse web

pages from a web server (example,
www.omnisecu.com), you are using either HTTP
(Hypertext Transfer Protocol) or HTTPS
(Hypertext Transfer Protocol Secure). The
browser you are using must request web pages
from the web server using HTTP or HTTPS and the Lecture 7: Network Topology
web server must response back to your computer
using HTTP or HTTPS. A network topology is the physical layout of
computers, cables, and other components on a
network. There are a number of different network
topologies, and a network may be built using
How HTTP (Hypertext Transfer Protocol) or HTTPS
multiple topologies. The different types of
(Hypertext Transfer Protocol Secure) should work
network layouts are Bus topology, Star topology,
were defined initially as a common standard.
Mesh topology, Ring topology, Hybrid topology
HTTP was defined initially as RFC (Request for
and Wireless topology. This lesson explains what
Comments) 2616. HTTPS (HTTP over TLS) was
is bus topology.
defined initially as RFC (Request for Comments)
2818. Anyone can follow the updated versions Bus Topology
these common standards (defined as RFC
(Request for Comments). ) and create their own A bus topology consists of a main run of cable
Browser or Web server products. with a terminator at each end. All nodes like
workstations, printers, laptops, servers etc., are
Now, think about the main benefit in following a connected to the linear cable. The terminator is
common standard. We made a common language used to absorb the signal when the signal
so that everyone can speak together without the reaches the end, preventing signal bounce. When
help of a translator! We achieved interoperability! using bus topology, when a computer sends out a
signal, the signal travels the cable length in both
Click next link to learn more about RFC (Request
directions from the sending computer. When the
for Comments).
signal reaches the end of the cable length, it
bounces back and returns in the direction it came
from. This is known as signal bounce. Signal
bounce may create problems in the computer
network, because if another signal is sent on the
cable at the same time, the two signals will
collide. Collisions in a computer network can
drastically reduce the performance of the
computer network.

Advantages

 Easy to connect a computer or peripheral

to a linear bus.
 Requires less cable length than a star
topology.

Disadvantages of Bus Topology

 Entire network shuts down if there is a break in

the main cable.

 Terminators are required at both ends of the

backbone cable.

 Difficult to identify the problem if the entire

network shuts down.

 Not meant to be used as a stand-alone solution.

Star Topology

A star topology is designed with each node (like

workstations, printers, laptops, servers etc.) connected
directly to a central device called as a network switch.
Each workstation has a cable that goes from its network
interface card (NIC) to a network switch.

Most popular and most widely used LAN technology

Ethernet operates in Star or Star-Bus topology.

Advantages of Star Topology

 Easy to install and wire.

 No disruptions to the network when connecting
or removing devices.
 Easy to detect faults and to remove parts.

Disadvantages of Star Topology

 Requires more cable length than a linear bus

topology.

• If the connecting network device (network switch)

fails, nodes attached are disabled and cannot participate
in computer network communication.

• More expensive than linear bus topology because of

the cost of the connecting devices (network switches).