This document provides an introduction to computer networks. It defines a network as a set of connected devices that can send and receive data. It discusses different types of network topologies including star, bus, ring and tree. It also covers the differences between peer-to-peer and client-server networks. Local area networks (LANs), wide area networks (WANs), and metropolitan area networks (MANs) are introduced as categories of networks defined by their geographical size.

1. Introduction to computer
Networks
Courtesy : This PPT has been compiled
from various internet sources.
1 Dr. Thanikaiselvan V / SENSE / VIT University

2. Computer Network
• A network is a set of devices (often referred to as nodes)
connected by communication links. A node can be a computer,
printer, or any other device capable of sending and/or
receiving data generated by other nodes on the network. A link
can be a cable, air, optical fiber, or any medium which can
transport a signal carrying information.
2 Dr. Thanikaiselvan V / SENSE / VIT University

3. Network Criteria
• Performance
• Depends on Network Elements
• Measured in terms of Delay and Throughput
• Reliability
• Failure rate of network components
• Measured in terms of availability/robustness
• Security
• Data protection against corruption/loss of data due to:
• Errors
• Malicious users
3 Dr. Thanikaiselvan V / SENSE / VIT University

4. Physical Structures
• Type of Connection
• Point to Point - single transmitter and receiver
• Multipoint - multiple recipients of single transmission
• Physical Topology
• Connection of devices
• Type of transmission - unicast, mulitcast, broadcast
4 Dr. Thanikaiselvan V / SENSE / VIT University

5. Network categories
• Two basic types of networks
• Peer-to-Peer Networks
• Client/Server Networks
5 Dr. Thanikaiselvan V / SENSE / VIT University

6. Peer-to-Peer Networks
• In a peer-to-peer network, all
computers are considered
equal; they all have the same
abilities to use the resources
available on the network.
• Example : Windows
Workgroup
Dr. Thanikaiselvan V / SENSE / VIT University6

7. Client/Server Networks
• Some nodes (SERVER) are dedicated to present
services to other nodes (CLIENTS)
• Primary-Secondary
• Examples:
• Mail Server
• Web Server
Dr. Thanikaiselvan V / SENSE / VIT University7

8. Client Server Model
Client Server
Initiates a request
Replies with a service
Client
Client
Dr. Thanikaiselvan V / SENSE / VIT University8

9. TOPOLOGY
• Topology defines the physical and logical arrangement of
links in a network
• Categories of topology
1.Mesh
2. Star
3. Tree
4. Bus
5. Ring
9 Dr. Thanikaiselvan V / SENSE / VIT University

10. Network Topologies
• Topology refers to the shape of a network, or the
network's layout.
• Type of connection
• How different nodes in a network are connected to
each other and how they communicate are
determined by the network's topology.
• The choice of topology is dependent upon
• Type and number of equipment being used
• Cost
Dr. Thanikaiselvan V / SENSE / VIT University10

11. Mesh topology
11
• In a mesh topology each device/PC is connected to
every other device/PC in the network by its own
cable
• n(n-1)/2
• N-1 --- I/O ports needed Dr. Thanikaiselvan V / SENSE / VIT University

12. 12
Advantages
• No traffic
• Robust
• Privacy and security
• Easy fault identification
Disadvantages
• N-1 I/O ports
• Installation and
reconfiguration is difficult
• Bulk wiring
• It can be used only for
limited application
•
Dr. Thanikaiselvan V / SENSE / VIT University

13. Star topology
• In a star topology, each device has dedicated point-point link
only to a central controller, usually called a hub.
• A Star topology does not allow direct traffic between devices.
• The controller acts as an exchange
13 Dr. Thanikaiselvan V / SENSE / VIT University

14. Star types
14
• Broadcasted Star
Topology (Hubbed
Star)
• Switched Star
Topology (Switched
Star)
Dr. Thanikaiselvan V / SENSE / VIT University

15. Star Advantages
• Single computer failure doesn’t bring down
whole network
• Adding new devices to a Star network is very
simple compared to any of the other topologies
• No disruptions to the network when connecting
or removing devices.
• Centralized control
• Centralized network/hub monitoring
• Easy to troubleshoot
Dr. Thanikaiselvan V / SENSE / VIT University15

16. Star Disadvantages
• If central device fails, the whole network fails
• Compared to the bus topology, a star network
generally requires more cable
• More expensive than linear bus topologies
because of the cost of the central device
Dr. Thanikaiselvan V / SENSE / VIT University16

17. Hubbed Star Rule
17
• Hubs simply pass on all the information they receive.
• Therefore, a large number of directly connected hubs cause a
lot of traffic, making the network vulnerable to collisions.
• This limits the number of hubs you can connect together.
• The maximum number of allowed repeater hops is four.
Dr. Thanikaiselvan V / SENSE / VIT University

18. Bus topology
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• All devices are connected to a central cable, called
the bus or backbone.
Dr. Thanikaiselvan V / SENSE / VIT University

19. Bus Topology
19
• Both ends of the network must be terminated
with a terminator.
• A barrel connector can be used to extend the
network.
Dr. Thanikaiselvan V / SENSE / VIT University

20. • Advantages
1. Easy installation
2. Backbone cable is
most efficient path
3. Less cabling
4. Easy extension
20
• Disadvantages
1. Fault finding
2. Signal degradation
3. Addition of new devices
with limited length of
cable
4. Stops all the
transmission when a
fault or break in the bus.
5. Signal reflection to origin
will create noise.
Dr. Thanikaiselvan V / SENSE / VIT University

21. Ring topology
• All devices are connected to one another in the shape of
a closed loop, so that each device is connected directly
to two other devices, one on either side of it.
• Data is passed one way from device to device.
21 Dr. Thanikaiselvan V / SENSE / VIT University

22. Ring topology
• A short message (called a token) is circulated around the
ring, being passed from station to station.
• The token originates from a controller or master station
which inserts it onto the ring.
• A station which wants to transmit waits for the token to
arrive.
• When the token arrives, the station changes it from a
token to a connector message, and appends its
message. This new message is then placed on the
outgoing side of the ring.
22 Dr. Thanikaiselvan V / SENSE / VIT University

23. Ring Advantages and
Disadvantages
• Advantages
• Equal access for all users
• Perform well under heavy traffic
• Disadvantages
• If one device/cable fails then the whole network goes
down.
• Difficult to troubleshoot
• Adding/Removing computers disrupts the whole
network
23 Dr. Thanikaiselvan V / SENSE / VIT University

24. Frame Transmission - Ring LAN
24 Dr. Thanikaiselvan V / SENSE / VIT University

25. Frame Transmission - Ring LAN
25 Dr. Thanikaiselvan V / SENSE / VIT University

26. Frame Transmission - Ring LAN
26 Dr. Thanikaiselvan V / SENSE / VIT University

27. Frame Transmission - Ring LAN
27 Dr. Thanikaiselvan V / SENSE / VIT University

28. Tree Topology
28 Dr. Thanikaiselvan V / SENSE / VIT University

29. Tree Topology
• Tree topology is a variation of star
• Central hub (Active Hub) controls the traffic of the
network
• The majority of devices connect to a secondary
hub(passive hub) that in turn is connected to the central
central hub.
• Advantages and Disadvantages are similar to star
• Example : Cable TV
29 Dr. Thanikaiselvan V / SENSE / VIT University

30. Hybrid Topology
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31. Categories of Networks
• Local Area Networks (LAN)
• A LAN is a group of computers connected in small geographical area
• Allow users to share files and services
• A LAN normally covers an area less than 2 miles.
• Wide Area Networks (WAN)
• A WAN is a group of computers connected in Large geographical area
such as country
• A WAN often connects two LANs (WAN Link)
• A WAN can be worldwide
• Metropolitan Area Networks (MAN)
• A MAN connects an area larger than a LAN but smaller than a WAN, such
as a city, with dedicated or high-performance hardwares
• Span tens of miles
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32. LAN, WAN and MAN
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33. LAN
• A LAN is a network that is used for communicating
among computer devices, usually within an office
building or home
• LAN’s enable the sharing of resources such as files or
hardware devices that may be needed by multiple users
• Is limited in size, typically spanning a few hundred
meters, and no more than 2 miles
• Is very fast, with speeds from 10 Mbps to 10 Gbps
• Requires very little wiring, typically a single cable
connecting to each device
• Has lower cost compared to MAN’s or WAN’s
Dr. Thanikaiselvan V / SENSE / VIT University33

34. WAN
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35. A heterogeneous network made of four WANs and two
LANs
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