Computer Network

1. Introduction
Chapter 1

2. Computer Networks
Computer network connects
two or more autonomous
computers.
The computers can be
geographically located
anywhere.
Introduction to Computer Networks

3. Network Components
Physical Media
Interconnecting Devices
Computers
Networking Software
Applications
Introduction to Computer Networks

4. Networking Media
Networking media can be
defined simply as the
means by which signals
(data) are sent from one
computer to another
(either by cable or wireless
means).
Introduction to Computer Networks

5. Networking Devices
HUB, Switches, Routers,
Wireless Access Points,
Modems etc.

6. Computers: Clients and Servers
In a client/server network
arrangement, network
services are located in a
dedicated computer whose
only function is to respond
to the requests of clients.
The server contains the
file, print, application,
security, and other services
in a central computer that
is continuously available to
respond to client requests.
Introduction to Computer Networks

7. Networking Protocol: TCP/IP
Introduction to Computer Networks

8. Applications
E-mail
Searchable Data (Web Sites)
E-Commerce
News Groups
Internet Telephony (VoIP)
Video Conferencing
Chat Groups
Instant Messengers
Internet Radio
Introduction to Computer Networks

9. Uses of Computer Networks
•Business Applications
•Home Applications
•Mobile Users
•Social Issues

10. Business Applications of Networks
• A network with two clients and one server.

11. Business Applications of Networks (2)
• The client-server model involves requests and replies.

12. Home Network Applications
•Access to remote information
•Person-to-person communication
•Interactive entertainment
•Electronic commerce

13. Home Network Applications (2)
• In peer-to-peer system there are no fixed clients and servers.

14. Home Network Applications (3)
• Some forms of e-commerce.

15. Mobile Network Users
• Combinations of wireless networks and mobile computing.

16. Applications of Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Email
Message broadcast
Remote computing
Distributed processing (GRID Computing)
Introduction to Computer Networks

17. Network Hardware
•Local Area Networks
•Metropolitan Area Networks
•Wide Area Networks
•Wireless Networks
•Home Networks
•Internetworks

18. Broadcast Networks
•Types of transmission technology
•Broadcast links
•Point-to-point links

19. LAN, MAN & WAN
Network in small geographical Area (Room, Building or a
Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area Network)
Network spread geographically (Country or across Globe) is
called WAN (Wide Area Network)
Introduction to Computer Networks

20. Broadcast Networks (2)
• Classification of interconnected processors by scale.

21. Local Area Networks
• Two broadcast networks
• (a) Bus
• (b) Ring

22. Network Topology
The network topology
defines the way in which
computers, printers, and
other devices are
connected. A network
topology describes the
layout of the wire and
devices as well as the
paths used by data
transmissions.
Introduction to Computer Networks

23. Bus Topology
Commonly referred to as a
linear bus, all the devices
on a bus topology are
connected by one single
cable.
Introduction to Computer Networks

24. Star & Tree Topology
The star topology is the most
commonly used architecture in
Ethernet LANs.
When installed, the star topology
resembles spokes in a bicycle
wheel.
Larger networks use the extended
star topology also called tree
topology. When used with network
devices that filter frames or packets,
like bridges, switches, and routers,
this topology significantly reduces
the traffic on the wires by sending
packets only to the wires of the
destination host.
Introduction to Computer Networks

25. Ring Topology
A frame travels around the ring,
stopping at each node. If a node wants
to transmit data, it adds the data as
well as the destination address to the
frame.
The frame then continues around the
ring until it finds the destination node,
which takes the data out of the frame.
Single ring – All the devices on the
network share a single cable
Dual ring – The dual ring topology
allows data to be sent in both
directions.
Introduction to Computer Networks

26. Mesh Topology
The mesh topology
connects all devices
(nodes) to each other for
redundancy and fault
tolerance.
It is used in WANs to
interconnect LANs and for
mission critical networks
like those used by banks
and financial institutions.
Implementing the mesh
topology is expensive and
difficult.
Introduction to Computer Networks

27. Metropolitan Area Networks
• A metropolitan area network based on cable TV.

28. Wide Area Networks
• Relation between hosts on LANs and the subnet.

29. Wide Area Networks (2)
• A stream of packets from sender to receiver.

30. Wireless Networks
•Categories of wireless networks:
•System interconnection
•Wireless LANs
•Wireless WANs

31. Wireless Networks (2)
• (a) Bluetooth configuration
• (b) Wireless LAN

32. Wireless Networks (3)
• (a) Individual mobile computers
• (b) A flying LAN

33. Home Network Categories
•Computers (desktop PC, PDA, shared peripherals
•Entertainment (TV, DVD, VCR, camera, stereo, MP3)
•Telecomm (telephone, cell phone, intercom, fax)
•Appliances (microwave, fridge, clock, furnace, airco)
•Telemetry (utility meter, burglar alarm, babycam).

34. Network Software
•Protocol Hierarchies
•Design Issues for the Layers
•Connection-Oriented and Connectionless Services
•Service Primitives
•The Relationship of Services to Protocols

35. Network Software
Protocol Hierarchies
• Layers, protocols, and interfaces.

36. Protocol Hierarchies (2)
• The philosopher-translator-secretary architecture.

37. Protocol Hierarchies (3)
• Example information flow supporting virtual communication in layer

38. Design Issues for the Layers
• Addressing
• Error Control
• Flow Control
• Multiplexing
• Routing

39. Connection-Oriented and Connectionless
Services
• Six different types of service.

42. Service Primitives
• Five service primitives for implementing a simple connection-oriented
service.

43. Service Primitives (2)
• Packets sent in a simple client-server interaction on a connection-
oriented network.

44. Services to Protocols Relationship
• The relationship between a service and a protocol.

45. Reference Models
•The OSI Reference Model
•The TCP/IP Reference Model
•A Comparison of OSI and TCP/IP
•A Critique of the OSI Model and Protocols
•A Critique of the TCP/IP Reference Model

46. Reference Models
The OSI
reference
model.

50. Reference Models (2)
• The TCP/IP reference model.

51. Reference Models (3)
• Protocols and networks in the TCP/IP model initially.

52. Comparing OSI and TCP/IP Models
•Concepts central to the OSI model
•Services
•Interfaces
•Protocols

53. A Critique of the OSI Model and
Protocols
•Why OSI did not take over the world
•Bad timing
•Bad technology
•Bad implementations
•Bad politics

54. Bad Timing
• The apocalypse of the two elephants.

55. A Critique of the TCP/IP Reference
Model
•Problems:
•Service, interface, and protocol not distinguished
•Not a general model
•Host-to-network “layer” not really a layer
•No mention of physical and data link layers
•Minor protocols deeply entrenched, hard to replace

56. Hybrid Model
• The hybrid reference model to be used in this book.

57. Example Networks
•The Internet
•Connection-Oriented Networks:
X.25, Frame Relay, and ATM
•Ethernet
•Wireless LANs: 802:11

58. The ARPANET
• (a) Structure of the telephone system.
• (b) Baran’s proposed distributed switching system.

59. The ARPANET (2)
• The original ARPANET design.

60. The ARPANET (3)
• Growth of the ARPANET (a) December 1969. (b) July 1970.
• (c) March 1971. (d) April 1972. (e) September 1972.

61. NSFNET
• The NSFNET backbone in 1988.

62. Internet Usage
•Traditional applications (1970 – 1990)
•E-mail
•News
•Remote login
•File transfer

63. Architecture of the Internet
• Overview of the Internet.

64. ATM Virtual Circuits
• A virtual circuit.

65. Ethernet
• Architecture of the original Ethernet.

66. Wireless LANs
• (a) Wireless networking with a base station.
• (b) Ad hoc networking.

67. Wireless LANs (2)
• The range of a single radio may not cover the entire system.

68. Wireless LANs (3)
• A multicell 802.11 network.

69. Network Standardization
•Who’s Who in the Telecommunications World
•Who’s Who in the International Standards World
•Who’s Who in the Internet Standards World

70. ITU
•Main sectors
• Radiocommunications
• Telecommunications Standardization
• Development
•Classes of Members
• National governments
• Sector members
• Associate members
• Regulatory agencies

71. IEEE 802 Standards
The 802 working groups. The important ones are
marked with *. The ones marked with  are
hibernating. The one marked with † gave up.

72. Metric Units
• The principal metric prefixes.

73. References
Books
Andrew S. Tanenbaum, Computer Network, Prentice-Hall
Doughlas E. Comer, Computer Networks and Internet
http://www.cisco.com/public/support/tac/documentation.
html
http://www.redhat.com/docs
http://home.iitk.ac.in/~navi/sidbinetworkcourse