A computer network connects devices using physical transmission media. There are three main network types: local area networks (LANs) which connect devices in a small area like a school; metropolitan area networks (MANs) which connect multiple LANs over a larger area like a city; and wide area networks (WANs) which connect over long distances like continents. Key network concepts include client-server models, intranets which privately share information within an organization, and five common network topologies like star, mesh, ring, bus and hybrid configurations. Hubs broadcast data to all ports while switches intelligently forward data to specific target devices, providing faster and more efficient networking.

1. COMPUTER NETWORK
RIFDHY RM
(Cyber Security Engineer)
Networking Module

2. 1. What is a computer network? Briefly describe with examples
A set of devices connected to each other using a physical transmission medium. For
Example, A computer network is a group of computers connected with each other to
communicate and share information and resources like hardware, data, and software.
2. What are the main network types? Explain.
There are mainly three types of computer networks based on their size:
1. Local Area Network (LAN)
▪ Local area network is a group of computers connected with each other in a small
place such as school, hospital, apartment etc.
▪ LAN is secure because there is no outside connection with the local area network
thus the data which is shared is safe on the local area network and can’t be
accessed outside.
▪ LAN due to their small size are considerably faster, their speed can range
anywhere from 100 to 100Mbps.
▪ LANs are not limited to wire connection, there is a new evolution to the LANs
that allows local area network to work on a wireless connection
2. Metropolitan Area Network (MAN)
MAN, network covers larger area by connections LANs to a larger network of
computers. In Metropolitan area network various Local area networks are connected
with each other through telephone lines. The size of the Metropolitan area network is
larger than LANs and smaller than WAN (wide area networks), a MANs covers the
larger area of a city or town
3. Wide area network (WAN)
Wide area network provides long distance transmission of data. The size of the WAN
is larger than LAN and MAN. A WAN can cover country, continent or even a whole
world. Internet connection is an example of WAN. Other examples of WAN are
mobile broadband connections such as 3G, 4G etc.

3. 3. Describe followings with examples
o Client computer and Server Computer
Client/Server computing is a computing model in which client and server computers
communicate with each other over a network. In client/server computing, a server
takes requests from client computers and shares its resources, applications and/or data
with one or more client computers on the network, and a client is a computing device
that initiates contact with a server in order to make use of a shareable resource.
o Intranet and extranet
▪ Intranet:
Intranet is owned by a single organization and is a tool for sharing information
throughout the organization. It is the type of Internet that is used privately. Since,
intranet is a private network so no one can use the intranet whose have not valid
username and password. In intranet, there are a limited number of connected
devices as compared to internet. Intranet is highly secure and has a small number of
visitors. It is used in order to get employee information, telephone directory etc.
▪ Extranet:
Extranet is owned by either a single or a many organization. It is managed on a
contractual basis between organizations and is a tool for sharing information
between the internal members and external members. Like intranet, it is also a
private network so only those who have a valid username and password can use the
extranet. Extranet is used to check status, access data, send mail, place order etc.
o Guided & unguided media
▪ Guided − In guided media, transmitted data travels through cabling system that
has a fixed path. For example, copper wires, fibre optic wires, etc.
▪ Unguided − In unguided media, transmitted data travels through free space in form
of electromagnetic signal. For example, radio waves, lasers, etc.

4. o Standalone emails & web-based emails.
▪ Web-based emails
You can access Web mail from any Internet-connected device, whereas you can
only use an email client on the specific device the client software is installed on.
Web mail, however, can only be read when you are online, unlike client-based
email which usually provides offline access. Also, clients can often be set up to
retrieve messages from Web mail accounts, such as Gmail, Yahoo or
Outlook.com, so you can read email from your Web mail provider in the client of
your choice
.
▪ Standalone emails
Webmail (or web-based email) is any email client implemented as a web
application running on a web server. Examples of webmail software are Round
cube and Squirrel Mail. Examples of webmail providers are AOL Mail, Gmail,
Outlook.com/Hotmail.com, Rackspace Email, Yahoo! Mail and Ice Warp Mail
Server. Many webmail providers also offer email access by a desktop email client
using standard email protocols, while many internet service providers provide a
webmail client as part of the email service included in their internet service
package.
4. What are the five main networking topologies? Describe using examples.
1. Mesh Topology
In mesh topology each device is connected to every other device on the network
through a dedicated point-to-point link. When we say dedicated it means that the link
only carries data for the two connected devices only. Let’s say we have n devices in
the network then each device must be connected with (n-1) devices of the network.
Number of links in a mesh topology of n devices would be n(n-1)/2
2. Star Topology
In star topology each device in the network is connected to a central device called
hub. Unlike Mesh topology, star topology doesn’t allow direct communication
between devices, a device must have to communicate through hub. If one device

5. wants to send data to other device, it has to first send the data to hub and then the hub
transmits that data to the designated device
3. Bus Topology
In bus topology there is a main cable and all the devices are connected to this main
cable through drop lines. There is a device called tap that connects the drop line to the
main cable. Since all the data is transmitted over the main cable, there is a limit of
drop lines and the distance a main cable can have
4. Ring Topology
In ring topology each device is connected with the two devices on either side of it.
There are two dedicated point to point links a device has with the devices on the
either side of it. This structure forms a ring thus it is known as ring topology. If a
device wants to send data to another device then it sends the data in one direction,
each device in ring topology has a repeater, if the received data is intended for other
device then repeater forwards this data until the intended device receives it.
5. Hybrid topology
A combination of two or more topology is known as hybrid topology. For example, a
combination of star and mesh topology is known as hybrid topology.
5. What is the difference between hub & switch? Explain.
▪ Hub
A hub is to send out a message from one port to other ports. For example, if there are
three computers of A, B, C, the message sent by a hub for computer A will also come to
the other computers. But only computer A will respond and the response will also go out
to every other port on the hub. Therefore, all the computers can receive the message and
computers themselves need to decide whether to accept the message.

6. ▪ Switch
A switch is able to handle the data and knows the specific addresses to send the
message. It can decide which computer is the message intended for and send the
message directly to the right computer. The efficiency of switch has been greatly
improved, thus providing a faster network speed.
▪ What Is the Difference?
Hub Vs. Switch
A hub works on the physical layer (Layer 1) of OSI model while Switch works on the
data link layer (Layer 2). Switch is more efficient than the hub. A switch can join
multiple computers within one LAN, and a hub just connects multiple Ethernet devices
together as a single segment. Switch is smarter than hub to determine the target of the
forwarding data. Since switch has a higher performance, its cost will also become more
expensive.