This document provides an overview of data communication networks. It discusses the components, structure, topology and types of networks. The key points are: Network performance is measured by throughput and delay, while reliability looks at frequency of failures and recovery time. A network connects two or more devices with links in various topologies like bus, star, ring and mesh. Wide area networks span hundreds of kilometers while personal area networks are within a few meters. Circuit switched networks establish dedicated circuits for transmission while packet switched networks use store-and-forward routing to transmit packets.

1. Communication
Networks
- Overview of Data
Communication
[Part 2]

2. What you will learn in this video
•Effectiveness of
Data
Communication
•Components of
Data
Communication
Data
Communication
•Text
•Numbers
•Audio
•Video
Data
Representation
•Simplex
•Half Duplex
•Full Duplex
Flow of Data
•Requirements
•Physical Structure
•Topology
•Types of Network
Network Basics

3. Networks
A network is the
interconnection of a set
of devices capable of
communication
Criteria for Network:
A network must be able
to meet a certain
number of criteria. The
most important of these
are
• Performance,
• Reliability,
• Security.

4. Requirements of a Network
• Generally we can measure the performance using 2 factors
• Throughput - network throughput refers to how much data can
be transferred from source to destination within a given
timeframe. Throughput measures how many packets arrive at
their destinations successfully
• Delay – total time taken for a packet to reach the destination
from source.
Performance
• Network reliability is measured by the frequency of failure, the
time it takes a link to recover from a failure, and the network’s
robustness in a catastrophe.
Reliability
• Network security issues include protecting data from
unauthorized access, protecting data from damage and
development, and implementing policies and procedures for
recovery from breaches and data losses.
Security

5. Structure of a Network
• A network is two or more devices connected through links. A link is
a communications pathway that transfers data from one device to
another.
• There are two possible types of connections:
• Point-to-Point
• A point-to-point connection provides a dedicated link between two devices. The
entire capacity of the link is reserved for transmission between those two devices.
• Multipoint
• A multipoint (also called multidrop) connection is one in which more than two
specific devices share a single link. In a multipoint environment, the capacity of the
channel is shared, either spatially or temporally.

6. Network Topology
• The term physical topology refers to the way in which a network is
laid out physically.
• The topology of a network is the geometric representation of the
relationship of all the links and linking devices (usually called nodes)
to one another.
• There are four basic topologies possible:
Bus Star Ring Mesh

7. Bus Topology
• One long cable acts as a
backbone to link all the devices in
a network. Nodes are connected
to the bus cable by drop lines and
taps.
• A tap is a connector that either
splices into the main cable or
punctures the sheathing of a
cable to create a contact with the
metallic core.
• A drop line is a connection
running between the device and
the main cable.
Advantages of Bus Topology
1. Ease of installation.
2. Less cabling is required when compared to other
topologies
Disadvantages of Bus Topology
1. Difficult for reconnection and Fault Isolation
2. Adding of new devices is tedious
3. Degradation of signal quality due to taps
4. Cable termination is needed so as to avoid signal
reflection.

8. Star Topology
• In a star topology, each device
has a dedicated point-to-point
link only to a central controller,
usually called a hub.
• The devices are not directly
linked to one another. Star
topology does not allow direct
traffic between devices.
• The controller acts as an
exchange: If one device wants to
send data to another, it sends the
data to the controller, which then
relays the data to the other
connected device.
Advantages of Star Topology:
1. Less expensive.
2. Each device needs only one link and one I/O port to connect
it to a network.
3. Easy to install and reconfigure.
4. Less cabling is required
5. Robustness is high. If one link fails, only that link is
affected. All other links remain active.
Disadvantages of Star Topology:
1. Whole Topology depends on HUB. If the HUB goes down
then the entire network is down.

9. Ring Topology
❖In a ring topology, each device has
a dedicated point-to-point
connection with only the two devices
on either side of it.
❖A signal is passed along the ring in
one direction, from device to device,
until it reaches its destination.
❖Each device in the ring incorporates
a repeater.
❖When a device receives a signal
intended for another device, its
repeater regenerates the bits and
passes them along.
Advantages of Ring Topology:
1. Easy to install and reconfigure
2. Addition or deletion of a system in topology
only requires alteration at 2 points
3. Fault Identification is easier
Disadvantages of Ring Topology:
1. Supports only Unidirectional Traffic
2. Any break in the ring can disable the entire
network.

10. Mesh Topology
• In a mesh topology, every device has a
dedicated point-to-point link to every other
device.
• The term dedicated means that the link carries
traffic only between the two devices it
connects.
• The number of physical links in a fully
connected mesh network with n nodes, we need
n (n – 1) physical links (Simplex Links).
• However, if each physical link allows
communication in both directions (duplex
mode), we need n (n – 1) / 2 duplex-mode
links.
• To accommodate that many links, every device
on the network must have n – 1 input/output
(I/O) ports to be connected to the other n – 1
station.
Advantages of Mesh Topology:
1. Dedicated Links can carry their own load,
Sharing reduces the link capacity
2. Robust – Data is still delivered even if one
link is down.
3. Privacy and Security – No eavesdropping
4. Fault Identification is easier
Disadvantages of Mesh Topology:
1. Installation is difficult due to complex wiring
2. Requires more IO Ports to connect the
systems.

11. Network Topology - Summary
Bus Star Ring Mesh

12. Types of Networks
WAN
Wide Area Network
Hundreds and Thousands of Kilo Meters
MAN
Metropolitan Area Network
Tens of Kilo Meters
LAN
Local Area Network
Hundreds of Meters
PAN
Personal Area Network
Few Square Meters
Classification Based
on Size and Coverage
Classification Based
on Switching
Switching represents that how the message is
forwarded to the destination network or system
Circuit Switched
Network
Packet Switched
Network

13. Circuit Switched Networks
• They are widely used in the telephone networks.
• It first establishes a dedicated circuit across a sequence of links
• Then it allows source node to send a stream of bits across this circuit
to a destination

14. Packet Switched Networks
• These networks are widely used in most of the applications
• Messages are transmitted as packets
• They follow store and forward concept of transferring
packets
• Packets may take any route and they are routed by the
intermediate routers.
• These packets are rearranged at the receiver side.
• Many discrete networks are interconnected together to
form a internetwork or INTERNET.
• Nodes are addressed logically so that they can be
identified by the neighbouring devices in the network
• Packet transmission occurs in 3 modes, they are:
1. Unicast
2. Multicast
3. broadcast

15. Circuit Switched Vs Packet Switched
All the systems are connected
as Single network
Interconnections of Multiple
Networks

16. A heterogeneous network made of four
WANs and three LANs

17. References:
• Behrouz A. Forouzan, ―Data communication and Networking, Fifth
Edition, Tata McGraw – Hill, 2013
• Larry L. Peterson, Bruce S. Davie, ―Computer Networks: A Systems
Approach, Fifth Edition, Morgan Kaufmann Publishers, 2011.
• Few online References (Will be Mentioned in the description Section)
Thank You…