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Outline
• Introduction to Computer Networks
• Goals
Introduction to Computer Networks
• Applications
• Communication model
Swagat Ranjan Sahoo • Categories of networks
Assistant Professor
• Network Structure and Architecture
Department of Computer Science and Engineering
GL Bajaj Institute of Technology and Management, Greater Noida-201306,
India

Person3/10/2025
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Introduction to Computer Networks Introduction to Computer Networks

• A set of devices often mentioned as nodes connected by media link is • The best example of a computer network is the Internet
called a Network • A computer network does not mean a system with one Control Unit
• A node can be a device which is capable of sending or receiving data connected to multiple other systems as its slave
generated by other nodes on the network like a computer, printer etc • That is a distributed system
• These links connecting the devices are called Communication
channels
• Computer network is a telecommunication channel using which we
can share data with other computers or devices, connected to the
same network
• It is also called Data Network

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Goals of Computer Networks Goals of Computer Networks

• Resource Sharing: Many organizations has a substantial • Inter process Communication: Network users, located
number of computers in operations which are located apart geographically apart, may converse in an interactive session
• Ex A group of office workers can share a common printer fax, modem, through the network
scanner etc. • In order to permit this, the network must provide almost error free
communications
• High Reliability If there are alternate sources of supply, all files
could be replicated on two or, machines • Flexible access: Files can be accessed from any computer in
• If one of them is not available, due to hardware failure, the other the network.
copies could be used • The project can be begun on one computer and finished on another.

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Goals of Computer Networks Applications of Computer Networks

• Business: E-commerce, online collaboration
• Security: It refers to the protection of data from any • Education: E-learning, virtual labs
unauthorized user or access. • Healthcare: Remote consultations, data sharing
• While travelling through network, data passes many layers of • Entertainment: Video streaming, online gaming
network, and data can be traced if attempted.
• Hence security is also a very important characteristic for
Networks.

• Cost Reduction: Centralized services and efficient resource

usage

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Communication model Communication model

Basic Communication Model Basic Communication Model
• A Communication model is used to exchange data between two parties. • Transmitter: The data generated by the source system is not directly
• For example: communication between a computer, server and transmitted in the form its generated
telephone (through modem • The transmitter transforms and encodes the data in such a form to
produce electromagnetic waves or signals
• Transmission System: A transmission system can be a single transmission
line or a complex network connecting source and destination
• Receiver: Receiver accepts the signal from the transmission system and
• Source : Data to be transmitted is generated by this device, converts it into a form which is easily managed by the destination device
example: telephones, personal computers etc. • Destination: Destination receives the incoming data from the receiver

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Communication model Categories of Networks

Characteristic of Communication model
1) Delivery- The System must deliver the data to the correct Destination.
2) Accuracy- The System must deliver the data at Accurate way.
3) Timeline - The System must deliver the data at Exact Time.
4) Jitter - It refers to the variable in the perfect arrival time

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Categories of Networks Categories of Networks

• The Network allows computers to connect and communicate with There are other types of Computer Networks also, like :
different computers via any medium • PAN (Personal Area Network)
• LAN MAN and WAN are the three major types of networks designed • SAN (Storage Area Network)
to operate over the area they cover • EPN (Enterprise Private Network)
• There are some similarities and dissimilarities between them • VPN (Virtual Private Network)
• One of the major differences is the geographical area they cover
• LAN covers the smallest area
• MAN covers an area larger than LAN
• WAN comprises the largest of all

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Categories of Networks Categories of Networks

Local Area Networks (LAN) Local Area Networks (LAN)
• LAN or Local Area Network connects network devices in such a way that personal • One can use it for an office building, home, hospital, school, etc.
computer and workstations can share data, tools and programs. • LAN is easy to design and maintain. A Communication medium used for LAN has
• The group of computers and devices are connected together by a switch, or stack twisted pair cables and coaxial cables. It covers a short distance, and so the error
of switches, using a private addressing scheme as defined by the TCP/IP protocol. and noise are minimized.
• Routers are found at the boundary of a LAN, connecting them to the larger WAN. • Early LANs had data rates in the 4 to 16 Mbps range. Today, speeds are normally
• Data transmits at a very fast rate as the number of computers linked are limited. 100 or 1000 Mbps.
• LANs cover smaller geographical area (Size is limited to a few kilometers) and are • Advanced LAN has speed in the range of 100 to 400 Gbps.
privately owned. • The fault tolerance of a LAN is more and there is less congestion in this network.

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Categories of Networks Categories of Networks

Local Area Networks (LAN) Metropolitan Area Networks (MAN)
• MAN or Metropolitan area Network covers a larger area than that of a LAN and
Advantages of LAN:
smaller area as compared to WAN.
• Share resources efficiently
• It connects two or more computers that are apart but resides in the same or
• Support heterogeneous different cities .
hardware/software • It covers a large geographical area and may serve as an ISP (Internet Service
• Access to other LANs and WANs Provider ).
• High transfer rates with low error rates • MAN is designed for customers who need a high speed connectivity Speeds of
MAN ranges in terms of Mbps.
• It’s hard to design and maintain a Metropolitan Area Network.
• The fault tolerance of a MAN is less and also there is more congestion in the
network .

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Categories of Networks Categories of Networks

Metropolitan Area Networks (MAN) Wide Area Networks (WAN)
• It is costly and may or may not be owned by • WAN or Wide Area Network is a computer network that extends over a large
a single organization geographical area, although it might be confined within the bounds of a
• Devices used for transmission of data state or country .
through MAN are Modem and Wire/Cable • A WAN could be a connection of LAN connecting to other LAN’s via
• Examples of a MAN are the part of the telephone lines and radio waves and may be limited to an enterprise (a
telephone company network that can corporation or an organization ) or accessible to the public.
provide a high speed DSL line to the • The technology is high speed and relatively expensive.
customer or the cable TV network in a city • There are two types of WAN:
• Switched WAN
• Point to Point WAN

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Categories of Networks Categories of Networks

Wide Area Networks (WAN) Wide Area Networks (WAN)
• Switched WAN: network is used to • WAN is difficult to design and maintain.
connect multiple end nodes through
a common WAN network, example is • Similar to a MAN, the fault tolerance of a WAN is less and there is more
Asynchronous Transfer Mode (ATM) congestion in the network.
network • A Communication medium used for WAN is Public Switched Telephone Network
• Point to Point WAN: is one which (PSTN)or Satellite Link.
consists of a two end nodes • Due to long distance transmission, the noise and error tend to be more in WAN.
connected by a leased line, example
is a dial-up line that connects a home • WAN’s data rate is slow about a 10th LAN’s speed, since it involves increased
computer to the Internet distance and increased number of servers and terminals etc.
• Speeds of WAN ranges from few kilobits per second (Kbps) to megabits per
second (Mbps).
• Devices used for transmission of data through WAN are: Optic wires,
Microwaves and Satellites.
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Categories of Networks Organization of Internet

Differentiate Between LAN, MAN and WAN • Core (Backbone) Network:
• The highest level of the Internet consists of high-capacity, high-speed
networks called backbones.
• Backbone providers (Tier 1 ISPs) form the core of the Internet, directly
interconnecting with one another.
• Regional Networks (Tier 2 ISPs):
• These connect to the backbone and provide service to smaller networks.
• They often act as intermediaries between the backbone and access
networks.
• Access Networks (Tier 3 ISPs):
• Local ISPs provide direct access to homes, offices, and individuals

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Internet Internet
• The network formed by a co-operative interconnection of large number of Key milestones in evolution of Internet
computer networks.
• Late 1960’s: US Department of Defense (DOD) funded a research
• The Internet is a global network connecting millions of computers. More than agency ARPA to do research on Networking. Only few computers
100 countries are linked into exchanges of data, news and opinions.
were connected.
• It is also called as network of networks
• ARPA: Advance Research Project Agency.
• It is a network of networks that use the standard Internet protocol
suite (TCP/IP). • 1970: ARPANET was useful for defence proposes. It was having its
• The Internet carries an extensive range of information resources and services, first step towards transmission control protocol.
such as the inter-linked hypertext documents of the World Wide Web (WWW). • 1971: Universities were added to the network. telnet and FTP were
• Graphical representation of the Internet available
• 1972: First Electronic mail was sent
• 1973: ARPANET connected to England and Norway
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Internet Internet
Key milestones in evolution of Internet Some facts
• 1974: TCP was recognized as a standard and used for communicating • 1994: Hotmail stats web-based email
across a system of network • 1994: The World Wide Web Consortium (W3C) was founded
• 1982: US DOD started building a defense data network based on • 1995: Java source code was released
ARPANET technology.
• 1998: Google was founded
• 1983: ARPANET splits into ARPANET and MILNET. MILNET has some
extra security requirements
• 1986: National Science Foundation (NSF) implements NFSNET
• 1991: ARCHIE and GOPHER FTP search engines were released
• 1993: World Wide Web (www) was used

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Internet Internet
Who Owns the Internet? Is Web and Internet the Same?
• No one actually owns the Internet, and no single person or • The Internet is not synonymous with World Wide Web.
organization controls the Internet in its entirety. • Internet is a massive network of networks, a networking
• The Internet is more of a concept than an actual tangible entity, and infrastructure.
it relies on a physical infrastructure that connects networks to other • It connects millions of computers together globally, forming a
networks. network in which any computer can communicate with any other
• Every person who makes a connection owns a slice of internet. computer as long as they are both connected to the Internet.
• The World Wide Web, or simply Web, is a system of interlinked
hypertext documents accessed via internet.
• It is an information-sharing model that is built on top of the
Internet(act as the backbone).
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Internet Organization of Internet

Internet Service Providers (ISPs)
World Wide Web Internet
An organization that maintain one or more gateway computers and provides
The World Wide Web, or simply Web, is The Internet is a global network of internet access facility to other user by allowing them to connect their computer
a system of interlinked hypertext computers that is accessed by the World to its own gateway computer(s) by using a modem.
documents accessed via internet. wide web. Example: BSNL, Airtel, Reliance jio, etc.
ISPs categorized into multiple layers:
The world wide web is a service. The Internet is an infrastructure. • Tier 1 ISPs: Large international companies providing backbone connectivity.
• Tier 2 ISPs: Regional ISPs connected to Tier 1 providers.
The world wide web is software- The Internet is hardware-oriented. • Tier 3 ISPs: Local ISPs connected to Tier 2 providers, serving end users.
oriented.

The world wide web uses HTTP. The Internet uses IP Addresses.

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Networks Structure and Architecture Network Architecture

Functionalities Network Architecture Protocols

Requirement: Converting digital data to analog data and vice versa Physical

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Network Architecture Network Architecture

L3 Switch or Router

L2 Switch

Network

Data Link Data Link

Requirement: Ensure proper scheduling in media access Physical Requirement: Find out suitable path to transfer data Physical

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Network Architecture Network Architecture

• Computer Network Architecture is defined as the physical and logical design
of the software, hardware, protocols, and media of the transmission of data
• Simply we can say that how computers are organized and how tasks are
allocated to the computer
• The two types of network architectures are used

Transport

Network

Data Link

Requirement: End to end traffic control in the network Physical

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Network Architecture Network Architecture

Peer To Peer network Peer To Peer network
• Network in which all the computers are linked together with equal • A network in which all the computers are linked
privilege and responsibilities for processing the data. together with equal privileges and responsibilities
• Peer To Peer network is useful for small environments, usually up for processing the data.
to 10 computers. • Peer-to-peer networks are useful for small
• Peer To Peer network has no dedicated server. environments, usually up to 10 computers.
• Special permissions are assigned to each computer for sharing the • Peer To Peer network has no dedicated server.
resources, but this can lead to a problem if the computer with the • Special permissions are assigned to each computer
resource is down. for sharing the resources,
• if the computer with the resource is down, this can
lead to a problem
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Network Architecture Network Architecture

Advantages Of Peer To Peer Network Client-Server Network
• It is less costly as it does not contain any dedicated server. • Client-Server network is a network model designed for the end
• If one computer stops working but, other computers will not users called clients, to access resources such as songs, video, etc.
stop working. from a central computer known as a Server.
• It is easy to set up and maintain as each computer manages • The central controller is known as a server while all other
itself. computers in the network are called clients
Disadvantages Of Peer To Peer Network • A server performs all the major operations such as security and
• In the case of Peer To Peer network, it does not contain the network management.
centralized system . Therefore, it cannot back up the data as the • A server is responsible for managing all the resources such as
data is different in different locations. files, directories, printer, etc.
• It has a security issue as the device is managed itself.
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Network Architecture Network Architecture

Advantages Of Client-Server Network
Client Server Network
• A Client-Server network contains a centralized system, therefore we can
• All the clients communicate with each back up the data easily
other through a server. • It has a dedicated server that improves the overall performance
• For example, if client1 wants to send
• Security is better in Client-Server network as a single server administers
some data to client 2, then it first sends the shared resources
the request to the server for the
• It also increases the speed of the sharing of resources
permission. The server sends the Disadvantages Of Client-Server Network:
response to the client 1 to initiate its • Client-Server network is expensive as it requires a server with large
communication with the client 2.
memory.
• A server has a Network Operating System(NOS) to provide the
resources to the clients, but the cost of NOS is very high.
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Network Topology Network Topology

The topology of a network is the geometric representation of the

relationship of all the links and linking devices (nodes) to one another.

bus

mesh

ring
star
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Network Topology Network Topology

Mesh Topology Mesh Topology
• Every link is dedicated point-to-point link Example
• The term dedicated means that the link carries • 8 devices in mesh has links: n(n-1) / 2
traffic only between the two devices it connects
• To link n devices fully connected mesh has: • number of links = 8 (8-1)/2 = 28
n ( n - 1) / 2 physical channels (Full-Duplex) • number of ports per device = n – 1 = 8 –1 = 7
• Every Device on the network must have
n - 1 ports Mesh Mesh

Note: Mesh topology is implemented in a limited fashion; e.g., as backbone of

hybrid network

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Network Topology Network Topology

Mesh Topology Mesh Topology
Advantages Disadvantages
• Each connection carry its own data • Big amount of cabling
load (no traffic problems) • Big number of I/O ports
• A mesh topology is robust • Installation and reconnection are difficult
• Privacy or security • Sheer bulk of the wiring can be greater
Mesh than the available space Mesh
• Fault identification and fault isolation
• Hardware connect to each I/O could be
expensive

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Network Topology Network Topology

Star Topology Star Topology
• Dedicated point-to-point to a central Advantages
controller (Hub) • Less expensive than mesh
• No direct traffic between devices (1 Link + 1 port per device)
• The control acts as an exchange Star • Easy to install and reconfigure Star
• Less cabling
• Additions, moves, and deletions required
one connection
• Robustness : one fail does not affect others
• Easy fault identification and fault isolation
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Network Topology Network Topology

Star Topology Bus Topology
Disadvantages • It is multipoint
• Dependency of the whole topology on one • One long cable acts as a backbone Bus
single point (hub) • Used in the design of early LANS, and
• More cabling than other topologies ( ring or Star Ethernet LANs
bus) • Nodes connect to cable by drop lines and
taps
• Signal travels along the backbone and
Note: Used in LAN some of its energy is transformed to heat
• Limit of number of taps and the distance
between taps
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Network Topology Network Topology

Bus Topology Ring Topology
Advantages • Each device has dedicated point-to-point
connection with only the two devices on either
• Ease of installation Bus side of it
• Less cables than mesh, star topologies • A signal is passed along the ring in one
direction from device to device until it reaches
Disadvantages its destination Ring
• Difficult reconnection and fault isolation ( limit of taps) • Each devices incorporates a Repeater
• Adding new device requires modification of backbone
• Fault or break stops all transmission
• The damaged area reflects signals back in the direction of the
origin, creating noise in both directions
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Network Topology Internet Governance Standards

Ring Topology • IETF (Internet Engineering Task Force)
• ICANN (Internet Corporation for Assigned Names and Numbers)
Advantages
• IANA (Internet Assigned Numbers Authority)
• Easy of install and reconfigure
• W3C (World Wide Web Consortium)
• Connect to immediate neighbors
• Move two connections for any moving (Add/Delete)
Ring
• Easy of fault isolation
Disadvantage
• Unidirectional
• One broken device can disable the entire network. This
weakness can be solved by using a dual ring or a switch
capable of closing off the break
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Thank you!

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