group of computers connected with each other to share information or resources. A network can be small or a large. it can be created in a building or spread all over the world. Networks are main source of communication all over the world. The most common resource shared today is connection to the Internet.

1. Computer Networks
Ch:5
Samina Khan
FAZAIA DEGREE COLLEGE RISALPUR

2. Contents
1. Introduction to networks
– Computer network
– Uses of networks
– Data transmission modes
– Network architecture
– Types of network architecture
2. Types of networks
3. Communication over networks

3. Computer network
• A computer network is a set of
computers that are connected
together so that they can share
information and resources.

5. Uses of networks
• Hardware sharing
• Software sharing
• File sharing
• Internet sharing

6. Hardware sharing
• Networks allow sharing of computer hardware such as
hard disk and printer.
• A hard disk can be attached to server to share it with
other network users.
• A single hard disk can provide storage space to many
computers.
• Similarly a single printer can be shared among many
computers.

8. Software sharing
• Application software can be installed on server and
shared over the network.
• There is no need to install it on every computer.

9. File sharing
• We can easily share files with other user over the
network.
• A user can place file in a shared location on one
computer and make it available to other users.
• User can access, modify and view information stored
on another computer in the network.

12. Internet sharing
• A single high speed internet can be shared with all
the users over the network.
• There is no need to provide separate internet
connection to every computer.

14. DATA TRANSMISSION MODES

15. Data transmission
modes
Simplex Half duplex Full duplex

16. Simplex Transmission Mode
• Provides data transmission in only one direction.
• One end is the sender and other is receiver.
• Transmission of data from keyboard to CPU or from
CPU to printer is always one direction.
• Examples: Radio and television transmission.

18. Half Duplex Transmission Mode
• Send and receive data in both direction but not
simultaneously.
• This kind of transmission can be seen in ATM
machines.

20. Full Duplex Transmission Mode
• Transmit information in both direction simultaneously.
• Full-duplex transmission mode are communication
between computers in a network and communication
over telephone line.

22. NETWORK ARCHITECTURE

23. Network architecture
• Layout of network
• It consists of computers, communication devices,
software, wired or wireless transmission of data and
connectivity between components.

24. Types of network architecture
• Client server network
• Peer to peer network
• Point-to-point network

25. Client/ server network
• A client/server network is a system where one or
more computers called clients connect to a central
computer named a server to share or use resources.
• In a client and server network, server shares its
resources such as hard disk, printers and Internet
connection with client computers.

26. Characteristics of client/server network
• It can be small as two computers and it can have
hundreds and even thousands of computers as well.
• It provides centralized security to ensure that
resources are not accessed by unauthorized users.
• Network administrator is responsible for sharing
resources, creating user accounts and assigning
privileges to all the users of the network.

28. Peer to peer network
• In a P2P network, the "peers" are computer systems
which are connected to each other via the Internet.
• Files can be shared directly between systems on
the network without the need of a central server.
• Each computer on a P2P network becomes a file
server as well as a client.

29. Characteristics of Peer-to Peer Network
• Each computer play the role of server, client or both
at the same time.
• Suitable for small number of users, ranging between
two to ten computers. Large Peer-to-Peer networks
become difficult to manage.
• It doesn’t provide centralized security.

31. Point to point network
• A point-to-point connection refers to a communications
connection between two communication end points or
nodes.
• Large networks that connect cities and countries.

32. Characteristics of Point-to-Point Network
• Used for long distance communication.
• There may be different paths for transmission of
information.

34. TYPES OF NETWORK

35. Types of networks based on geographical area
• LAN(Local Area Network)
• MAN(Metropolitan Area Network)
• WAN(Wide Area Network)

36. LAN(Local Area Network)
• LAN covers a limited area, ranging from a small office
to a campus or nearby buildings.
• Examples: Network within a school, college,
organization, hospital etc.

37. Characteristics of LAN
• Restricted to a limited area.
• Data transmission speed is fast.
• Data communication problems rarely occur.
• Transmission medium is owned by the user organization.

39. WAN(Wide Area Network)
• Spans a large geographical
area, connecting several
locations of an organization
across cities, countries and
continents.
• Example: Internet

40. MAN(Metropolitan Area Network)
• Falls between LAN and WAN.
• It spans area larger than a LAN
but smaller than a WAN.
• Example: Network used by
telecommunicating companies
for providing Cable TV and
Internet services.

42. PAN(Personal Area Network)
• A PAN is a computer network for interconnecting
electronic devices centered on an individual person's
workspace.
• A PAN provides data transmission among devices such as
computers, smart phones, tablets and personal digital
assistants.
• It can be wired( USB & FireWire technologies) or
wireless(Bluetooth or infrared connection).
• E.g Bluetooth network

45. Internet
• Internet is the largest computer network that
connects million of computers all over the world.
• Computers on the internet are connected together
using telephone lines, fiber optics or wireless signals.
• Each computer on the internet has an IP address.
• IP stands for internet protocol. It identifies each
computer on the internet with its location.

46. • World Wide Web(WWW) is the most popular and
widely used system to access the internet.
• It is a collection of websites available on the internet.
• Web browser is used to access websites.
• We enter the URL into a browser to access a website.

47. Network topology
• The physical arrangement of network nodes is called
network topology.
• A node represent a computer or a network device.

48. TYPES OF NETWORK TOPOLOGIES

49. Types of network topologies
• Bus topology
• Ring topology
• Star topology
• Mesh topology

50. Bus Topology
• A bus topology is a topology for a Local
Area Network (LAN) in which all the nodes are
connected to a single cable.
• The cable to which the nodes connect is called a
"backbone". If the backbone is broken, the entire
segment fails.

52. Advantages of bus topology
• Lowest cost due to short cable length.
• Easy to add new computers.
• Easy to setup.
• Suitable for small networks.

53. limitations
• If the backbone is broken, the entire segment fails.
• Difficult to detect and fix faults.

54. Ring Topology
• Shaped just like a ring.
• In a ring topology, all devices in the network are
connected via a cable that loops in a logical ring or
circle.
• All the messages travel in the same direction.

56. Advantages of Ring topology
• Managing is easier as to add or remove a device from
the topology only two links are required to be
changed.
• Server or switch is not required to manage network.
• All computers have equal opportunity to transmit
data.

57. Limitations
• A link failure can fail the entire network.
• Detection of fault is difficult.
• Data traffic issues, since all the data is circulating in a
ring.

58. Star topology
• In a star topology each device in the network is
connected to a central device called hub/switch.
• If one device wants to send data to other device, it
has to first send the data to hub and then the
hub/switch transmit that data to the designated
device.
• A switch can connect 4, 8, 16,24 or 32 nodes.
• A switch can be connected to another switch to
expand network.

60. Advantages of Star topology
• Easy fault detection
• Provides fast communication.
• Failure of one node doesn’t stop functioning of the
entire network.

61. Limitations of star topology
• If hub goes down everything goes down, none of the
devices can work without hub.
• More cables are required.
• Costly to implement.

62. Mesh Topology
• In a Mesh topology, all the network nodes/devices
are connected to all the other nodes/devices.
• Number of links in a mesh topology of n devices
would be n(n-1)/2.
• Message sent on a Mesh can take any possible path
from source to destination.
• Not commonly used since it is costly.

64. Advantages of Mesh topology
• Most reliable topology.
• No data traffic issues as there is a dedicated link
between two devices.
• It is secure because there is a point to point link thus
unauthorized access is not possible.

65. Limitations
• Most expensive because it requires more cables than
other topologies.
• Difficult to implement.
• Difficult to add new computer.

66. COMMUNICATION OVER NETWORKS

67. Communication via telephone networks
• Telephone network is commonly used for data
communications because it exists all over the world.
• Following are the communication lines provided via
telephone networks:
• Dial-up line
• Digital Subscriber Line(DSL)
• Integrated Services Digital Network(ISDN) lines
• Code Division Multiple Access (CDMA)

68. DIAL-UP line
• Dial-up line provide
standard telephone network
• Maximum speed of dial line
is 56 kilobits per second
which is very slow.
• It is being replaced by faster
DSL connection for internet.

69. Digital Subscriber Line (DSL)

70. DSL
• It provides high speed internet connection.
• It is called broadband because it has broad range of
frequencies for transmitting digital data.
• Its speed is 256KBPS
• DSL service is “always on” and lets you surf the web
while using your landline phone.

71. Integrated Service Digital Network (ISDN) line

72. Integrated Service Digital Network (ISDN) line
• It provide a maximum speed of 128kbps
• Faster then dial up line and slower than DSL lines
• It can transmit both voice and data at the same time.
• Sometimes DSL in villages can only reach speeds of 1
to 2 Mbps, so ISDN access is preferable.

74. Code Division Multiple Access (CDMA)
• It is a wireless cellular communication
technology
• Include short messaging ,voice, data
and video transmission
• Provide speed of several Mbps.

75. Code Division Multiple Access (CDMA

76. Code Division Multiple Access (CDMA