The document provides an introduction to computer networks including: 1. The origins and early development of the Internet from ARPANET in the 1960s-1980s. 2. The basic components, goals, and applications of computer networks including resource sharing, reliability, and performance. 3. The key hardware, software, and transmission media that enable computer networking including hubs, switches, routers, network interface cards, transmission control protocol, and fiber optic cables.

1. Note-1
Introduction to Computer Networks
Course Title : Computer Networks Theory
Course Code : CSE 317
Submitted To
Pranab Bandhu Nath
Senior Lecturer, Department Of CSE
City University, Dhaka
Submitted By
Mushahadur Rahaman Khan
ID: 1834902513
BSc in CSE (Day)
Batch: 49th

2. Derivation of Computer Network :
The Internet originated from a US Department of Defense research project called DARPA
It was then called ARPANET, and on January 14, 1969, the first network connection was established
between the University of California, Los Angeles and the Stanford Research Institute.
The first international network connection was established on July 25, 1983, with ARPANET
communication with the United States at University College London.
In 1973, Robert Kahn and Winton Surf of ARPANET first developed the Transmission Control Protocol
and the Internet Protocol - called TCPIP - which became the universal language of the Internet in the
1980s.
The first TCPIP test was conducted between Stanford University and University College London in 1985.
Two years later, TCPIP communication was tested between three networks in the United States, the
United Kingdom and Norway.
What is Computer Network :
Networks are an interconnection of two or more computers such that they can share resources and
information. These computers can be linked together using a wide variety of cables or telephone lines or
through satellites.
Goals of Computer Network
Resource Sharing : This is the main goal of a computer network. It means to make all programs
peripherals and data available to any one computer on the network to all other computers in the network
without regard to the physical locations of them. So sharing resources from one Computer to another
Computer over a network.
Reliability : A second goal is to provide high reliability by having alternative sources of
supply. For example, all files could be replicated on two or three machines, so if one of them is
Unavailable, the other copies could be available.
Performance : Another goal is to increase the systems performance, as the work load increases, by just
adding more processors.
Scalability : Scalability increases the system performance by adding more processors.
Security : Network security is not only concerned about the security of the computers at each end of the
communication chain; however, it aims to ensure that the entire network is secure.

3. Network security entails protecting the usability, reliability, integrity, and safety of network and data.
Effective network security defeats a variety of threats from entering or spreading on a network.
Application of Computer Network
Business Applications
Information services
Teleconferencing
Mobile Users
Communication Medium
e-commerce
Home Applications
Electronic commerce
E-mail etc.
Network Hardware & Software:
There are most basic three components of Computer Network.
1. Hardware Equipment
2. Software
3. Cables and Connectors
Hardware Equipment
Network devices, there are networking hardware, are physical devices that can be call required for
communication and interaction between hardware on a computer network.
Network Hub : A hub is a device that connects two or more computers in a computer network.

4. Network hubs are classified into two types like active hub & passive hub.
Active Hub : This type of hub increases the value of the signal and transmits the required signal by
eliminating unnecessary signals from the original signal.
Passive Hub : Inactive hubs only exchange information between computers. It does not increase the
value of the signal. For this reason, all these hubs are connected to the active device
Advantages-
✓ The price is low.
✓ Can connect different mediums.
Disadvantage-
✓ Network traffic increases.
✓ There is a possibility of interruption in data exchange.
✓ Data filtering is not possible.
Switch: A networking switch is a device that can filter and forward packets when exchanging
information packets between different parts of the local area network.
Advantages-
❖ There is no problem in exchanging data.
❖ Broadcasts can be controlled using a virtual LAN.
Disadvantages-
❖ The price is higher than the hub.
❖ Data cannot be filtered.
❖ The configuration is relatively complex

5. Router: Routing is the process of sending data from one network to another. And the hardware
used for this routing is the router.
Advantages of the Router-
o Reduces problems with data transmission.
o Data filtering is possible.
o Can connect different types of networks such as Ethernet, tokens, rings, etc.
Disadvantages of the Router-
o Routers cost more.
o The router cannot be connected without the same protocol network.
o The configuration is relatively complex.
Brouter : Brouters are a combination of router and bridge . Brouters are operated in network
layer(routable protocols) & data link layer. Brouter provides combine features of router for routing
protocol & bridge for non-routable protocol .

6. Modem : Modem is the short form of Modulator and Demodulator. A modem is a communication
device or transmission system, it performs input and output functions simultaneously, a computer system
must have a modem to transmit or receive data over an Internet connection. The main function of a
modem in a computer system is to transmit data from the computer and on the other hand the computer
receives the same data from the modem.
Repeater: The data signal flows through the network media after passing a certain distance and
gradually weakens due to attenuation. Then this signal has to be amplified or strengthened to reach the
destination. The device that does this from the middle position is called the repeater.
Bridges: A bridge is a network device used to connect multiple LANs.The process of aggregating
networks is called network bridging. A bridge connects the different components so that they appear as
parts of a single network.

7. Gateway : Gateways are used to connect different types of networks. Devices like hubs, switches,
routers, etc. do not facilitate protocol translation, but they do facilitate gateways. It works on protocol
translation when connected to different networks. Gateways can be divided into several parts according to
the type of work. One of them is Address Gateway, Protocol Gateway, Application Gateway etc.
Server : A server is a computer that accepts a request from another computer or device and provides
information accordingly.

8. Client : In a client-server architecture, the client works on a small computer that is used by the
organization's employees to perform daily activities. Employees use client computers to access data files
or applications stored on server machines.
Peer : Peer to peer is short for Pitupi. In this method, two devices can be connected without any main
server. Basically, it is used more for file sharing. The computers that are connected here, some are just
servers or some are just clients. Every connected computer has the ability to share files and download
files with everyone.
Transmission: Data transmission is the process of sending digital or analog data over a communication
medium to one or more computing, network, communication or electronic devices. It enables the transfer

9. and communication of devices in a point-to-point, point-to multipoint and multipoint-to multipoint
environment.
Medium : A medium is a third-party or element through which a message is communicated. This seems
to apply to information technology as well as to seances. In information technology, a medium can be: 1.
A physical transmission medium such as optical fiber 2. A presentation medium.
NIC: The network interface card or LAN card works on this interface. This network adapter can allow
the computer to connect to any media. There are different network adapters for different media and those
computers can be connected to the network with suitable connectors.
Software
Software : Software, instructions that tell a computer what to do. Software comprises the entire set of
programs, procedures, and routines associated with the operation of a computer system. The term was
coined to differentiate these instructions from hardware—i.e., the physical components of a computer
system. A set of instructions that directs a computer’s hardware to perform a task is called a program, or
software program.
Network Operating System : Network Operating System is a computer operating system that
facilitates to connect and communicate various autonomous computers over a network. An Autonomous

10. computer is an independent computer that has its own local memory, hardware, and O.S. It is self capable
to perform operations and processing for a single user
Protocols Switches : A protocol is a rule or guideline followed by each computer for data
communication. A protocol suite is a set of related protocols that are laid down for computer
networks.
Computer Network Cables And Connectors
In use, the computer network cable consists of several types that are usually adjusted to the needs,
conditions, network topology, protocols and the size of a certain computer network. For example, there
are small computer network cables that are used in small amounts ,but there are also almost unlimited
uses of computer network cables.
There are at least 3 types of cables.
Coaxial cable
Twisted pair cable
Fiber-optic cable
Coaxial Cable : Co-axial cable is made by wrapping a thin but stiff copper wire covered with insulated or
worn electrical material in the shape of a lattice with another conductive wire and metallic foil. It is so
named because the axes of both wires are the same.

11. Twisted Pair: Twisted pair cable consists of two copper wires and a non-conductive material is used to
separate the two. This cable usually has 4 pairs of wires together and each pair has a common color
(white) and the rest of the wires are different colors. Twisted pair cables have a range no farther than 100
meters, The speed varies from 10 Mbps to 10000 Mbps (10 Gbps).
Fiber optic cable : Optical fiber is simply a very thin type of glass fiber. How it works: Using full
internal reflection technology, it works with light signals instead of electrical signals and uses laser beams
to exchange data.
Fiber Optic Advantages :
o Able to transmit signals at high speed
o Simple and also flexible
o Can transmit pulses
o Resistant to radio or electromagnetic waves

12. Reference :
1. https://www.computerhope.com/jargon/a/arpanet.htm
2. https://www.britannica.com/technology/computer-network
3. https://sunwebblog.files.wordpress.com/2018/04/2-goals-and-applications-of-network.pdf
4. https://www.elprocus.com/what-are-network-devices-and-their-types
5. https://learntomato.flashrouters.com/what-is-a-client-what-is-a-server-what-is-a-host
6. https://www.tutorialspoint.com/what-is-network-interface-card-nic
7. https://www.zion-communication.com/Types-of-Computer-Network-Cables-id3499964.html
8. https://www.vskills.in/certification/tutorial/network-cabling-and-connectors/
9. https://www.google.com/search?q=fiber+optic+cable+&tbm=isch&ved=2ahUKEwiaptrgyr7wAh
XHQn0KHUGmC_IQ2-
cCegQIABAA&oq=fiber+optic+cable+&gs_lcp=CgNpbWcQAzIECAAQQzIECAAQQzIECAA
QQzIECAAQQzICCAAyAggAMgIIADICCAAyAggAMgIIAFD6qh9Y-
qofYNayH2gAcAB4AIAB2QWIAdkFkgEDNi0xmAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&
sclient=img&ei=vt-
YYJrPNseF9QPBzK6QDw&bih=657&biw=1366&rlz=1C1CHBF_enBD878BD878#imgrc=pnT
EEfVpHTqLNM
10. https://www.britannica.com/technology/software
11. https://afteracademy.com/blog/what-is-a-network-operating-
system#:~:text=Network%20Operating%20System%20is%20a,processing%20for%20a%20singl
e%20user.