Computer Network(CSC 503)

Shilpa Ingoley

Lecture 2
 Introduction to Networking
• “Computer Network means a collection of autonomous computers interconnected by a Single technology.”

Two computers are said to be

interconnected if they are able to
exchange information. Computers
can be connected using a copper wire,
fiber optics, microwaves, infrared, and
communication satellites

Computer network is an
interconnection of the various
computers to share the software,
hardware, resources and the data
through a communication medium
between them.
Five Components of Data Communication
• Message: Information(data) to be communicated
• Sender
• Receiver
• Transmission medium: Physical path by which a message travels
• Protocol: A set of rules that govern data communication

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Direction of Data Flow

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Data Flow
• Simplex
• Unidirectional
• As on a one-way street
• Half-duplex
• Both transmit and receive possible, but not at the same time
• Like a one-lane road with two-directional traffic
• Walkie-talkie, CB radio
• Full-duplex
• Transmit and receive simultaneously
• Like a two-way street, telephone network
• Channel capacity must be divided between two directions

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Network
• Network: A set of devices (nodes) connected by communication links
• Node: Computer, printer, or any device capable of sending and/or receiving data
• To be considered effective and efficient, a network must meet a number of criteria

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Need of Networking
• Access to remote programs
• Access to remote databases
• Communication Media
Goals of Computer Networks

• Resource Sharing
• High Reliability
• Scalability
• Communication
• Saving Money
Network application
• Business Applications
• Resource Sharing
• Server-Client model :
• Communication Medium
• eCommerce :

• Home Applications
• Access to remote information :
• Person-to-person communication :
• Interactive entertainment :
Business Applications (1)

A network with two clients and one server

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Business Applications (2)

The client-server model involves requests and replies

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Applications (1)

In a peer-to-peer system there are no fixed clients and

servers.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Home Applications (2)

Some forms of e-commerce

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Network software and hardware components
Hardware Components of n/w Software Components of n/w
• Server • Network Operating System
• Workstations • Core OS
• NICs • Client component
• Cabling and Connectors • NIC drivers
• Shared resources and • Network applications
peripherals
Interconnection networking devices
• Repeater
• Modems
• Hub
• Bridge
• Switch
• Routers
• Gateways
Categories of Networks

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LAN(Local Area Network)

• Usually privately owned

• A network for a single office, building, or campus  a few Km
• Common LAN topologies: bus, ring, star • LAN’s enable the sharing of
• Example: An isolated LAN connecting 12 computers to a hub in a closet resources such as files or
hardware devices that may be
needed by multiple users
• 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
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Contd…
MAN (Metropolitan Area Network)

• Designed to extend to an entire city

• Cable TV network, a company’s connected LANs
• Owned by a private or a public company

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WAN(Wide Area network)

• Long distance transmission, e.g., a country, a continent, the world

• Enterprise network: A WAN that is owned and used by one company

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Internetwork
• Internetwork (internet) : two or more networks are connected by internetworking
devices
• Internetworking devices: router, gateway, etc.
• The Internet: a specific worldwide network

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Internetwork Example
• A heterogeneous network : four WANs and two LANs

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