Computer networks

1. Computer Networks
CLASS NOTE-1
Lecturer
Pranab Bandhu Nath
Senior Lecturer
CSE Department
City University, Dhaka
STUDENT
NAME :MD HASNAIN
ID :1834902583
Department of CSE City University, Dhaka.

2. Lesson Title
Introduction to Computer Networks:
Basic concept of Computer networks Goals of
networking
Arpanet:
ARPANET was the network that became the basis for the Internet.
Based on a concept first published in 1967, ARPANET was developed
under the direction of the U.S. Advanced Research Projects Agency
(ARPA). In 1969, the idea became a modest reality with the
interconnection of four university computers. The initial purpose was to
communicate with and share computer resources among mainly
scientific users at the connected institutions. ARPANET took advantage
of the new idea of sending information in small units called packets
that could be routed on different paths and reconstructed at their
destination. The development of the TCP/IP protocols in the 1970s
made it possible to expand the size of the network, which now had
become a network of networks, in an orderly way.
• Advanced Research Projects Agency Network (ARPANET)
• U.S. Defense Department, funded the development of the Advanced
Research Projects Agency Network (ARPANET) in the late 1960s. Its
initial purpose was to link computers at Pentagon-funded research
institutions over telephone lines.
• At the height of the Cold War, military commanders were seeking a
computer communications system without a central core, with no
headquarters or base of operations that could be attacked and

3. destroyed by enemies thus blacking out the entire network in one fell
swoop.
• Defense Department put out a call for competitive bids to build the
network, and in January 1969 Bolt, Beranek, and Newman (BBN) of
Cambridge, Massachusetts, won the $1 million contract.
What is Computer Network?
• A computer network is a set of computers connected together for the
purpose of sharing resources. The most common resource shared today
is connection to the Internet. Other shared resources can include a
printer or a file server. The Internet itself can be considered a computer
network.
Goals of Computer Network
• Sharing Resources from one Computer to another Computer over a
network .
• Performance by measuring the speed of data transmission with
number of users, connectivity and the software used .
• Reliability makes easy to use an alternative source for data
communication in case of hardware failure or connectivity issues.
• Scalability increases the system performance by adding more
processors .

4. • Security is the main characteristics of Computer network where you
can take necessary steps for protecting your data from unauthorized
access.
Application of Computer Network
Computer network applications are network software applications that
utilize the Internet or other network hardware infrastructure to
perform useful functions for example file transfers within a network.
They help us to transfer data from one point to another within the
network.
• Business Applications : A business application is a collection of
components that provides a business functionality that you can use
internally, externally, or with other business applications. You can
create business applications of individual components, which are
related to each other.
• Communication Medium : Communication media refers to the
means of delivering and receiving data or information. In
telecommunication, these means are transmission and storage tools or
channels for data storage and transmission.
• e-commerce : Electronic commerce or e-commerce is a business
model that lets firms and individuals buy and sell things over the
internet. E-commerce operates in all four of the following major market
segments:

5.  Business to business
 Business to consumer
 Consumer to consumer
 Consumer to business
• Home Applications :The Home Application is where you can
choose the first screen you want to see when you log into your Keep &
Share account.
• Electronic commerce : Electronic commerce or e-commerce is a
business model that lets firms and individuals buy and sell things over
the internet. E-commerce operates in all four of the following major
market segments:
 Business to business
 Business to consumer
 Consumer to consumer
 Consumer to business
• Mobile Users : Mobile-user meaning A smartphone or tablet
user.
Network Hardware & Software
There are three component of Computer Network
1. Hardware Equipment
2. Software
3. Cables and Connectors

6. Hardware:
NIC: A network interface controller is a computer hardware component
that connects a computer to a computer network.
Server: Servers are computers designed to wait for any requests from users
or other computers and then act on that request. Their main purpose is to be
there for you, to share data and perform tasks to keep your workflow smooth
and productivity elevated.
Client: In computing, a client is a piece of computer hardware or
software that accesses a service made available by a server as part of
the client–server model of computer networks. The server is often (but
not always) on another computer system, in which case the client
accesses the service by way of a network.
Peers: In networking, a peer is a node that provides the same
functionality as another. For example, two desktop PCs in a network
are peers. A desktop PC and a server are not peers as they perform
different operations.
Transmission: Transmission line hardware is also called transmission
line fitting or transmission line accessory. Transmission line hardware is
a general called for all the fittings that used to connect the transmission
line. They can survive in the heavy saline conditions along the coast.
Medium: Medium is an open platform where readers find dynamic
thinking, and where expert and undiscovered voices can share their
writing on any topic.
Router: The router is a physical or virtual internetworking device that is
designed to receive, analyze, and forward data packets between
computer networks.

7. Bridge: A network bridge is a computer networking device that creates
a single, aggregate network from multiple communication networks or
network segments. This function is called network bridging.
Hub: When referring to a network, a hub is the most basic networking
device that connects multiple computers or other network devices
together.
Switches: A switch is a device in a computer network that connects
other devices together. Multiple data cables are plugged into a switch
to enable communication between different networked devices.
Gateway: A gateway is a piece of networking hardware or software
used in telecommunications for telecommunications networks that
allows data to flow from one discrete network to another. Gateways
are distinct from routers or switches in that they communicate using
more than one protocol to connect a bunch of networks and can
operate at any of the seven layers of the open systems interconnection
model.
Repeaters: In telecommunications, a repeater is an electronic device
that receives a signal and retransmits it. Repeaters are used to extend
transmissions so that the signal can cover longer distances or be
received on the other side of an obstruction.
Software:
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 computer is
an independent computer that has its own local memory, hardware,

8. and O.S. It is self capable to perform operations and processing for a
single user. They can either run the same or different O.S.
Network Protocol (TCP/IP, OSI): A network protocol is an established
set of rules that determine how data is transmitted between different
devices in the same network. Essentially, it allows connected devices to
communicate with each other, regardless of any differences in their
internal processes, structure or design. Network protocols are the
reason you can easily communicate with people all over the world, and
thus play a critical role in modern digital communications.
Cables and Connectors:
Twisted pair cable: Twisted pair cabling is a type of wiring in which two
conductors of a single circuit are twisted together for the purposes of
improving electromagnetic compatibility. Compared to a single
conductor or an untwisted balanced pair, a twisted pair reduces
electromagnetic radiation from the pair and crosstalk between
neighboring pairs and improves rejection of external electromagnetic
interference.
Coaxial cable : Coaxial cable, or coax is a type of electrical cable
consisting of an inner conductor surrounded by a concentric conducting
shield, with the two separated by a dielectric many coaxial cables also
have a protective outer sheath or jacket. The term "coaxial" refers to
the inner conductor and the outer shield sharing a geometric axis.
Fiber-optic cable: A fiber-optic cable, also known as an optical-fiber
cable, is an assembly similar to an electrical cable, but containing one
or more optical fibers that are used to carry light. The optical fiber
elements are typically individually coated with plastic layers and

9. contained in a protective tube suitable for the environment where the
cable is used. Different types of cable are used for different
applications.