Computer Network
(CEC408)
Ms. Neelam Joshi
Asst. Professor
Dept. of Computer Engineering,
FCRIT
Neelam.joshi151907@gmail.com
Cell. +91 7987130543
1
Module 1: Introduction to Networking
1.1 Basic concepts and fundamentals of data communication and computer
network, Basic Networking Devices: Repeater, Hub, Switch, Router, NIC,
Modem, Network Topologies, Type of networks (LAN, WAN, MAN)
1.2 Layers of OSI and TCP/IP Design Issues of Layers. Guided and
Unguided media. Switching– Circuit-switched Networks – Packet
Switching, Message switching
Text Books :
•
•
•
1. Computer Networks, A.S.Tanenbaum,4th edition, 2018 Pearson Education.
2. Data Communications and Networking, B.A. Forouzan, 5th edition, 2017,TMH.
3. A Top-Down Approach Featuring the Internet, James F. Kurose, Keith W. Ross, Computer Networking, 6th edition, 2017,
AddisonWesley.
Reference Books :
1. An Engineering Approach to Computer Networking, S. Keshav,1 Edition, 2007, Pearson
2. Computer Networks: Principles, Technologies & Protocols for Network Design, Natalia Olifer & Victor Olifer,
1 Edition, 2006 Wiley India.
3. Computer Networks: A Systems Approach, Larry L.Peterson, Bruce S.Davie, , Second Edition, 2011, The
Morgan Kaufmann Series in Networking
2
Introduction of Data Communication
& Computer Network
Transferring data over a transmission
medium between two or more devices,
systems, or places is known as data
communication.
A network is a group of connected
communicating devices such as computers
and printers.
An internet is two or more networks that can
communicate with each other.
3
Introduction of Computer Network
Introduction based
on:
A computer network is a group of devices
connected with each other through a
transmission medium such as wires, cables
etc. These devices can be computers,
printers, scanners, Fax machines etc. The
purpose of having computer network is to
send and receive data stored in other
devices over the network.
4
Network Criteria
Performance
Reliability
Security
5
Fundamental Characteristics of effective DC
Delivery
Accuracy
timeliness
Jitter
6
Components of Data Communication/CN
Message
Sender
Receiver
Transmis
sion
media
Protocols
7
Components of a data communication system
Key Elements of Protocols
Syntax
Semantics
Timing
9
Uses of Computer Networks

10
Business Applications:A network with
two clients and one server. The client-server
model involves requests and replies.
Mrs. Neelam Joshi
•
•
•
•
•
•
Payroll calculations
Budgeting
Sales analysis
Financial forecasting
Managing employee database
Maintenance of stocks, etc.
2/19/2025
Uses of Computer Networks
11
Banking
Marketing
Education
Healthcare
Mrs. Neelam Joshi
2/19/2025
Uses of Computer Networks
12
Military
Government
Communication
Engineering Design
Mrs. Neelam Joshi
2/19/2025
Transmission Modes
 The way in which data is transmitted from one device to another device is known
as transmission mode.
 The transmission mode is also known as the communication mode.
 Each communication channel has a direction associated with it, and transmission media
provide the direction. Therefore, the transmission mode is also known as a directional
mode.
 The transmission mode is defined in the physical layer.
 The Transmission mode is divided into three categories
13
Mrs. Neelam Joshi
2/19/2025
Data Flow/Transmission Mode
14
Data Flow/Transmission Mode
1. Simplex- A simplex communication channel only sends information
in one direction. For example, a radio station usually sends
signals to the audience but never receives signals from them,
thus a radio station is a simplex channel.
2. Half Duplex- In half duplex mode, data can be transmitted in both
directions on a signal carrier except not at the same time. At a
certain point, it is actually a simplex channel whose transmission
direction can be switched.
3. Full Duplex- A full duplex communication channel is able to
transmit data in both directions on a signal carrier at the same
time. It is constructed as a pair of simplex links that allows
bidirectional simultaneous transmission.
15
Transmission Technology of Computer Network
Point to Point
Broadcasting
Multicasting
16
Classification / Types of Network
Personal Area Network
Local Area Network
Metropolitan Area
Network
Wide Area Network
Internet
17
Classification / Types of Network
18
Classification / Types of Network(PAN)
2.
1.
19
Classification / Types of Network(LAN)
1.
20
2.
Classification / Types of Network(MAN)
1.
2.
21
Classification / Types of Network(WAN)
22
Comparison between LAN, MAN and WAN
What is Network Topology
Introduction based on:
Network topology is the arrangement of
the elements of a communication
network. Network topology can be used
to define or describe the arrangement of
various types of telecommunication
networks, including command and
control radio networks, industrial
fieldbusses and computer networks.
19
Network Topology
 Topology defines the structure of the network of how all the components are interconnected
to each other.
25
Mrs. Neelam Joshi
2/19/2025
BUS Topology
 Bus topology is a network type in which every computer and network
device is connected to single cable. When it has exactly two
endpoints, then it is called Linear Bus topology.
20
 Bus Topology:
 Stations are connected through a single backbone cable.
 Used in 802.3 (Ethernet) and 802.4 standard networks.
 The most common access method of the bus topologies
 CSMA (Carrier Sense Multiple Access):CSMA/CD,CSMA/CA


Advantages:

Low-cost cable and simple to implement

A failure in one node will not have any effect on other nodes.
Disadvantages:

27
Extensive cabling, Difficult troubleshooting and Reconfiguration
Mrs. Neelam Joshi
2/19/2025
RING Topology
 It is called ring topology because it forms a ring as each computer is
connected to another computer, with the last one connected to the first.
 Exactly two neighbors for each device
21
Ring Topology:

 Similar to bus topology, but with connected ends.
 The node that receives the message from the previous computer
will retransmit to the next node.
 The data flows in one direction, i.e., it is unidirectional.
 Access method of the ring topology is token passing.
 Advantages:
 Low-cost and simple to implement.
 Network Management is easy.

Disadvantages:
 Difficult troubleshooting and Reconfiguration.
 Communication
delay is directly proportional to the number of
nodes.
29
Mrs. Neelam Joshi
2/19/2025
Star Topology
In this type of topology all the computer connected via single hub
through cable.
22
 Star Topology
 Coaxial cable or RJ-45 cables are used
 Every node is connected to the central hub, or a switch.
 Most popular topology in network implementation.
 Advantages:
 Efficient troubleshooting
 Network Management is easy and easily expandable
 Limited failure.
 Cost effective
 Disadvantages:
 A Central point of failure.
 Cable requirement is more.
31
Mrs. Neelam Joshi
2/19/2025
TREE Topology
25



Tree Topology

Combines the characteristics of bus topology and star topology

All the computers are connected with each other in hierarchical
fashion.

There is only one path exists between two nodes for the data
transmission. Thus, it forms a parent-child hierarchy.
Advantages:

Support for broadband transmission

Easily expandable and manageable.

The breakdown in one station does not affect the entire network.

Error detection and error correction are very easy.
Disadvantages:
Difficult troubleshooting and reconfiguration
High cost due to backbone devices.


33
Mrs. Neelam Joshi
2/19/2025
MESH Topology
 It is a point-to-point connection to other nodes or devices. All the
network nodes are connected to each other.
23
Types of Mesh Topology
 Partial Mesh Topology : In this topology some of the systems are
connected in the same fashion as mesh topology but some devices are
only connected to two or three devices.
 Full Mesh Topology : Each and every nodes or devices are connected
to each other.
24
 Mesh Topology

Computers are interconnected with each other through various
redundant connections.

Used for WAN implementations where communication failures are a
critical concern.

Mesh topology is mainly used for wireless networks.

Mesh topology can be formed by using the formula:

Number of cables = (n*(n-1))/2;
 Advantages:

Reliable, fast communication and Easier Reconfiguration
 Disadvantages:

36
Costly
Mrs. Neelam Joshi
2/19/2025
HYBRID Topology
It is two different types of topologies which is a mixture of two or more topologies.
For example if in an office in one department ring topology is used and in another
star topology is used, connecting these topologies
26
 Hybrid Topology :
 Combination of various different topologies.
 Advantages:
 Reliable, Scalable, Flexible and Effective
 Disadvantages:
 Complex design and Costly infrastructure
38
Mrs. Neelam Joshi
2/19/2025
Network Hardware/Devices
Networking hardware, also known
as network equipment or computer
networking devices, are electronic devices
which are required for communication and
interaction between devices on a computer
network
37
Network Hardware/Devices
Network devices are physical devices that allow hardware on a
computer network to communicate and interact with each other.
Network devices like hubs, repeaters, bridges, switches, routers,
gateways, and brouters help manage and direct data flow in a
network.
They ensure efficient communication
between connected devices by controlling
data transfer, boosting signals, and linking
different networks. Each device serves a
specific role, from simple data forwarding
to complex routing between networks.
40
Network Devices
41
Network Hardware Components
 NIC(Network interface card): NIC helps the computer to
communicate with another device. The network interface
card contains the hardware addresses, the data-link layer
protocol use this address to identify the system on the
network so that it transfers the data to the correct destination.
 There are two types of NIC: wireless NIC and wired NIC.
 Wireless NIC: All the modern laptops use the wireless NIC.
In Wireless NIC, a connection is made using the antenna that
employs the radio wave technology.
 Wired NIC: Cables use the wired NIC to transfer the data
over the medium.
42
Mrs. Neelam Joshi
2/19/2025
Network Hardware Components
 Hub:
 Hub is a central device that splits the network connection into
multiple devices.
 When computer requests for information from a computer, it
sends the request to the Hub. Hub distributes this request to all the
interconnected computers.
 Switches :
 Switch is a networking device that groups all the devices over the
network to transfer the data to another device.
 Switch is better than Hub as it does not broadcast the message
over the network, i.e. it sends the message to the device for which
it belongs to.
 Therefore, we can say that switch sends the message directly from
source to the destination.
43
Mrs. Neelam Joshi
2/19/2025
Network Hardware Components
 Cables and connectors :
 Cable is a transmission media that transmits the communication
signal
 Router :
 Connects the LAN to the internet. The router is mainly used to
connect the distinct networks or connect the internet to multiple
computers.
 Modems:
 A modem acts as converter or translator. It allows digital data or
information to be transmitted over analog lines of transmission
such as a telephone line.
44
Mrs. Neelam Joshi
2/19/2025
Cable Types
45
Mrs. Neelam Joshi
Specification
CableType
10BaseT
UnshieldedTwisted Pair
10Base2
Thin Coaxial
10Base5
Thick Coaxial
100BaseT
UnshieldedTwisted Pair
100BaseFX
Fiber Optic
100BaseBX
Single mode Fiber
100BaseSX
Multimode Fiber
1000BaseT
UnshieldedTwisted Pair
1000BaseFX
Fiber Optic
1000BaseBX
Single mode Fiber
1000BaseSX
Multimode Fiber
2/19/2025
Network Hardware
40
Connection-Oriented Versus Connectionless Service
 Connection-oriented
service involves the creation and termination of the
connection for sending the data between two or more devices.
 Connectionless
service does not require establishing any connection and
termination process for transferring the data over a network.
47
Mrs. Neelam Joshi
2/19/2025
Parameter
Related System
Virtual path
Authentication
Data Packets Path
Bandwidth
Requirement
Data Reliability
Congestion
Examples
48
Connection-Oriented Service
Connection Less Service
It is designed and developed based
It is service based on the postal
on the telephone system.
system.
It creates a virtual path between the
Not
sender and the receiver.
It requires authentication before transmitting the It does not require authentication.
data packets to the receiver.
All data packets are received in the same order as Data packets are received in any
those sent by the sender.
order.
It requires a higher bandwidth to transfer the data It requires low bandwidth to transfer
packets.
the data packets.
It is a more reliable connection service because it It is not a reliable connection service
guarantees data packets transfer from one end to
the other end with a connection (ack).
There is no congestion as it provides an end-to- There may be congestion due to not
end connection between sender and receiver.
providing an end-to-end connection.
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP),
Internet Protocol (IP), Internet Control
Message Protocol (ICMP)
Mrs. Neelam Joshi
2/19/2025
Design Issues for the layers
Addressing
Direction of
transmission
Error control
Avoid loss of
sequencing
Ability of receiving
long messages
Multiplex and Demux
50
Design Issues for the Layers
 Reliability: Damaged or inverted bits can be identified
(error detection) and
corrected (error correction)
 Scalability
 Addressing
 Error Control
 Flow Control
 Resource Allocation
 Multiplexing
 Routing
 Security
50
Mrs. Neelam Joshi
2/19/2025
Layered Architecture
CS -602
SELO: 1,5,8,9
Reference Models: OSI& TCP/IP

52
OSI (Open System Interconnection) Reference Model:

It describes how information from a software application in one computer moves through
a physical medium to the software application in another computer.

OSI consists of seven layers, and each layer performs a particular network function.

Was developed by the International Organization for Standardization (ISO) in Each
layer is self-contained, so that task assigned to each layer can be performed
independently.

OSI model divides the whole task into seven smaller and manageable tasks. Each layer is
assigned a particular task.
Mrs. Neelam Joshi
2/19/2025
OSI Reference Model
53
Mrs. Neelam Joshi
2/19/2025
OSI Reference Model
54

The seven layers can be thought of as belonging to three subgroups.

Layers I, 2, and 3 - physical, data link, and network - are the network support layers; they deal
with the physical aspects of moving data from one device to another (such as electrical
specifications, physical connections, physical addressing, and transport timing and reliability).

Layers 5, 6, and 7 - session, presentation, and application - can be thought of as the user support
layers; they allow interoperability among unrelated software systems.

Layer 4- the transport layer, links the two subgroups and ensures that what the lower layers have
transmitted is in a form that the upper layers can use.

The upper OSI layers are almost always implemented in software; lower layers are a
combination of hardware and software, except for the physical layer, which is mostly hardware.
Mrs. Neelam Joshi
2/19/2025
An exchange using the OSI model
Name of
unit
exchang
ed
APDU PPDU
SPDU
Segments
Packet
Frame
Bit
55
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers
56
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Physical Layer
57

It is responsible for movements of individual bits from one hop (node) to the next.

Representation of bits: Bits are encoded into signals--electrical or optical.

Data transmission rate and mode of transmission: Number of bits sent per second;
simplex, half duplex or full duplex.

Line configuration: point-to-point or multipoint.

Physical topology

Synchronization of bits: sender and receiver must be synchronized at the bit level
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Data Link Layer

Responsible for the error-free transfer of data frames
Framing: Divides the stream of bits received from the network layer into manageable data units.
Physical addressing: Destination MAC address .
Flow control: This is used to avoid overwhelming the receiver if it is slower than the sender.
Error control: Trailer added to the end of the frame to detect errors.
Access control: More devices are connected to the same communication channel, determine which
device has control over the link at a given time.
58
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Data Link Layer

59
Hop to hop delivery
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Data Link Layer

Hop to hop delivery
60
60
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Network Layer
61

Responsible for the source-to-destination delivery of a packet, possibly across multiple
networks (links).

Internetworking: It provides a logical connection between different devices.

Logical Addressing: Adds the source and destination address to the header of the frame.
Addressing is used to identify the device on the internet.

Routing: Determines the best optimal path out of the multiple paths from source to the destination
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Transport Layer
⦁
Responsible for the delivery of a message from one process to another.
Service-point addressing: Port Address / Socket.
Segmentation and reassembly: A message is divided into transmittable segments by providing
sequence numbers.
Connection control: Connection oriented and connectionless.
Flow control: Flow control at this layer is performed end to end.
Error control: performed process-to process rather than across a single link.
62
Mrs. Neelam Joshi
2/19/2025
Process to process delivery
63
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Session Layer

Responsible for dialog control and synchronization

It establishes, maintains, and synchronizes the interaction among communicating systems.
64

Dialog control: Creates a dialog between two processes

Synchronization: Adds some checkpoints when transmitting the data in a sequence.

If some error occurs in the middle of the transmission of data, then the transmission will take
place again from the checkpoint.This process is known as Synchronization and recovery.
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Presentation Layer

Responsible for translation, compression, and encryption

It is concerned with the syntax and semantics of the information exchanged between two systems.

Translation: The sender changes the information from its sender-dependent format into a common
encoded format and vise versa at receiver side.

Compression: Data compression reduces the number of bits contained in the information.

Encryption: To ensure privacy.
65
Mrs. Neelam Joshi
2/19/2025
Functions of OSI Layers: Application Layer

Responsible for providing services to the user.
Network Virtual Terminal: Log on to a remote host.
 File transfer, access, and management (FTAM): Access, retrieve and manage file from a remote
system / host.
 Mail services: This application provides the basis for e-mail forwarding and storage.
 Directory services: This application provides distributed database sources and access for global
information about various objects and services.

66
Mrs. Neelam Joshi
2/19/2025
Reference Models: TCP/IP
TCP/IP Protocol Suite:

TCP/IP protocol suite was developed prior to the OSI model and the layers in TCP/IP do
not exactly match those in the OSI model.

The original TCP/IP protocol suite was defined as having four layers: host-to-network,
internet, transport, and application.

When TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of
five layers: physical, data link, network, transport, and application.
67
Mrs. Neelam Joshi
2/19/2025
Reference Models: OSI and TCP/IP
(Network Access Layer)
68
Mrs. Neelam Joshi
2/19/2025
Protocol Hierarchy
CS -602
SELO: 1,5,8,9
Information Flow in layered architecture
70
71
Mrs. Neelam Joshi
2/19/2025
TCP/IP Protocol Suite
72
Mrs. Neelam Joshi
2/19/2025
Functions of TCP/IP Layer
73
Mrs. Neelam Joshi
2/19/2025
TCP/IP Protocol Suite

TCP/IP is a hierarchical protocol (each upper-level protocol is supported by one or more
lower-level Protocols) made up of interactive modules, each of which provides a specific
functionality.

Contain relatively independent protocols that can be mixed and matched depending on the
needs of the system.

Physical and Data Link Layers (Network Access Layer)

At the physical and data link layers, TCP/IP does not define any specific protocol. It
supports all the standard and proprietary protocols.
74
Mrs. Neelam Joshi
2/19/2025
TCP/IP Protocol Suite
 Network Layer
 Supports the Internetworking Protocol (IP), in turn, uses four
supporting protocols: ARP,
RARP, ICMP, and IGMP.

The IP is the transmission mechanism used by the TCP/IP protocols.
 It is an unreliable and connectionless protocol-a best-effort delivery service
(that means no error checking or tracking).

IP assumes the unreliability of the underlying layers and does its best to get a transmission
through to its destination, but with no guarantees.

IP transports data in packets called datagrams, each of which is transported separately
along different routes and can arrive out of sequence or be duplicated.
75
Mrs. Neelam Joshi
2/19/2025
 Network Layer
TCP/IP Protocol Suite

Address Resolution Protocol (ARP): used to find the physical address of the node when
its Internet address is known.

Reverse Address Resolution Protocol (RARP): Allows a host to discover its Internet
address when it knows only its physical address.
 It is used when a computer is connected to a network for the first time or when a
diskless
computer is booted.

Internet Control Message Protocol (ICMP): used by hosts and gateways to send error
messages to the sender.

Internet Group Message Protocol (IGMP): Used to facilitate the
transmission of a message to a group of recipients.
76
Mrs. Neelam Joshi
simultaneous
2/19/2025
TCP/IP Protocol Suite
Transport Layer :
IP delivers a packet from one physical device to another (host-to-host).
UDP and TCP are transport level protocols responsible for delivery of a message from a
process (running program) to another process.
Stream Control Transmission Protocol (SCTP): provides support for
newer applications
such as voice over the Internet. It combines the best features of UDP and TCP.
User Datagram Protocol (UDP): It is simpler and unreliable. It adds only
port addresses,
checksum error control, and length information to the data from the upper layer.
77
Mrs. Neelam Joshi
2/19/2025
TCP/IP Protocol Suite

Transmission Control Protocol (TCP): provides full transport-layer services to
applications.

TCP is a reliable stream (connection-oriented) transport protocol.

At the sending end of each transmission,TCP divides a stream of data into smaller units called
segments.

Each segment includes a sequence number for reordering after receipt, together with an
acknowledgment number for the segments received.

At the receiving end,TCP collects each datagram as it comes in and reorders the transmission
based on sequence numbers.
 Application Layer:

It is equivalent to the combined session, presentation, and application layers in the OSI
model.

Many protocols are defined at this layer: SMTP, FTP, HTTP, DNS, SNMP,TELNET etc.
78
Mrs. Neelam Joshi
2/19/2025
Transmit Data Using Network Layers
TCP/IP Five Layer Software Model Terminology Reference
Relationship of layers and addresses in TCP/IP
81
Mrs. Neelam Joshi
2/19/2025
Transmission Media
The purpose of the
physical layer is to
Various physical media can be used for
transport bits from one
the actual transmission.
machine to another.
Transmission media is a communication
channel that carries the information from
the sender to the receiver.
27
Transmission Media Types
28
Guided Transmission Media
1. Transmission capacity depends
critically on the medium
2.Medium is point-to-point or
multipoint (e.g. LAN). Examples are coaxial cable, twisted pair, and optical
fiber.
29
Unguided Transmission Media
1. It provides a means for transmitting
electro-magnetic signals but do not
guide them.
2. Example wireless transmission.
30
Twisted Pair
Although the
bandwidth
characteristics of
magnetic tape are
excellent, the
delay
characteristics
are poor.
31
Coaxial Cable
It has better shielding and greater
bandwidth than unshielded twisted
pairs, so it can span longer distances at
higher speeds
is commonly used for analog
transmission and cable television.
CS -602
SELO: 1,5,8,9
32
Coaxial Cable
33
Fiber Optics Cable
34
Unguided Media
RadioTransmission
Radio frequency is easier to
generate and because of its large
wavelength it can penetrate
through walls and structures
alike. Radio waves can have
wavelength from 1 mm –
100,000 km and have frequency
ranging from 3 Hz (Extremely
Low Frequency) to 300 GHz
(Extremely High Frequency)
35
Microwave Transmission
Electromagnetic waves above 100 MHz tend to travel in a straight line
and signals over them can be sent by beaming those waves towards one
particular station. Because Microwaves travels in straight lines, both
sender and receiver must be aligned to be strictly in line-of-sight.
36
Infrared signals
Infrared signals can be used for short-range communication in a closed area
using line-of-sight propagation.
Used in short-range communications such as those between a PC and a peripheral device.
It can also be used for indoor LAN, remote controls, security systems and thermal imaging
cameras which detect people in the dark.
They are relatively directional, cheap, and easy to build but have a major
drawback: they do not pass through solid objects.
Advantage: Against eavesdropping is better that means no one sitting at next room or your
neighbor can not interfere/control your devices.
16
Switching
Switching is the process of transferring data
packets from one device to another in a network,
or from one network to another, using specific
devices called switches.
Switching takes place at the Data Link layer of
the OSI Model. This means that after the
generation of data packets in the Physical Layer,
switching is the immediate next process in data
communication.
94
Switching
95
Types Of Switching
There are three types of switching
methods:
Message Switching
Circuit Switching
Packet Switching
Datagram Packet Switching
Virtual Circuit Packet Switching
96
Types Of Switching
Message Switching: This is an older switching technique that has become
obsolete. In message switching technique, the entire data block/message is
forwarded across the entire network thus, making it highly inefficient.
Circuit Switching: In this type of switching, a connection is established
between the source and destination beforehand. This connection receives the
complete bandwidth of the network until the data is transferred completely.
Packet Switching: This technique requires the data to be broken down into
smaller components, data frames, or packets. These data frames are then
transferred to their destinations according to the available resources in the
network
at
a
particular
time.
This switching type is used in modern computers and even the Internet.
Datagram Packet Switching: In Datagram Packet switching, each
data frame is taken as an individual entity and thus, they are processed
separately. Here, no connection is established before data transmission
occurs.
Virtual-Circuit Packet Switching: In Virtual-Circuit Packet switching,
a logical connection between the source and destination is made before
97 transmitting any data. These logical connections are called virtual circuits.
Types Of Switching
Message Switching
98
Types Of Switching
99
66