Introduction to computer networks

Chapter 1 1

Introduction to Computer Networks

Chapter 1

Chapter 1 2

Chapter Objectives

Explain the need of networks Explain history of computer networks (ARPANET) Explain the types of computer networks Explain Client/Server configuration Explain layers of OSI model Explain network selection criteria Network Application Explain Standards Organizations

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Computer Network

Interconnection of two or more computers and peripherals

Allows user to share and transfer information

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Need of Computer Networks

Sharing Resources Reduced Cost Reduced time Scalability Reliability Security

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History of Computer Networks (ARPANET) ARPA designed for Department of Defense

(DOD), US Small computers were connected to large

mainframe computers IMPs were connected to each other through

modem Supported different operating systems Telenet and ftp services was provided by

ARPANET

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Types of Computer Networks

Networks are classified depending on the geographical area covered by the network

ComputerNetworks

Local Area Network

(LAN)

CampusArea Network

(CAN)

MetropolitanArea Network

(MAN)

WideArea Network

(WAN)

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Local Area Network (LAN) - I

Covers a small area Connects computers and workstations covering a

local area like, office or home

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Local Area Network (LAN) - II Advantages of LAN:

Improves productivity due to faster work Provides easy maintenance New systems can be installed and configured

easily Disadvantages of LAN:

Limited number of systems can only be connected Cannot cover large area Network performance degrades as number of

users exceeds

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Campus Area Network (CAN)

Made up of multiple LANs within limited area Connects different LANs in a campus

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Metropolitan Area Network

Interconnects networks within a city Supports data and voice transmission

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Wide Area Network Covers a wide geographical area which includes

multiple computers or LANs e.g. Internet

Comparison of Networks

LAN CAN MAN WAN

Connects computers and workstations in office or home.

Connects two or more LANs within a campus.

Interconnects networks in a town or a city.

Connects geographically separated LANs.

Covers a local area of 1 Km.

Covers privately owned campus with an area of 5 to 10 Kms.

Covers larger area than LAN but smaller area than WAN with an area of 2 to 100 Kms.

Spans large geographical area more than 100 Kms.

Data Transmission Rate – 10/100 Mbps

Data Transmission Rate – Variable

Data Transmission Rate - Variable

Data Transmission Rate – 64 Kbps or 2 Mbps

Uses IEEE 802 standard.

____ Uses IEEE 802 standard.

Uses ITU standard.

Low cost High cost High cost (Repetitive)

High cost (Repetitive)

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Chapter 1 13

Case Study - I

MoneyMaker is a bank having its registered office at Delhi. It has branches at Mumbai, Chennai, Hyderabad and Bangalore. The operating departments in the bank are Finance, Insurance, Loan, IT, Marketing, Customer Service and HR. MoneyMaker bank uses LAN as their computer network for each department. All the branches of the bank from different cities are connected through WAN. The bank is expanding and decided to open its branches at different locations in the city.

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Problem

Determine which type of network to be used within a city

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Suggested Solution

Use LAN computer network for each department in the new branch. MAN can be used for connecting the different branches of the bank within the city

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Client/Server Configuration

Consists of two elements, Client and Server Server:

A centralized element which provides resources to client

Manages data, printers or network traffic Client:

Manages local resources used by users such as monitor, keyboard, CPU and peripherals

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OSI Model

Run it through CBT

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Network Selection Criteria

Helps to improve network functionality

NetworkCriteria

Performance Reliability Security

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Network Applications

Financial Institution (Banking Sector) Communication Services (Telecom Industry) Internet Service (WWW, ISP)

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Standards Organizations Also known as Standards Development Organization

(SDO) Develop, maintain, improve and revise standards Classified as:

ISO – Creates world wide industrial and commercial standards

ITU-T – Standardizes and regulates international radio and telecommunication

IEEE – Develops standards for power & energy, IT, telecommunication, biomedical and healthcare

ANSI – Creates standards for computer industry e.g. FDDI

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Summary - I

Computer network enables the user to share data and network resources

Network allows remote users to communicate with each other

Computer networks are divided into LAN, CAN, MAN and WAN depending on the coverage area

LAN is a small network and easy to create Client/Server configuration also called as two-tier

architecture, consist of two nodes, client and server

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Summary – II

OSI model consists of seven layers and provides standards for computer communication

Physical layer is responsible for actual transmission of bits over the medium

Data Link layer is responsible for node to node delivery of frames

Network layer is responsible for end to end delivery of packets, and routing

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Summary - III

Transport layer is responsible for end to end delivery of the entire message

Session layer is responsible for establishing, managing and terminating sessions

Presentation layer is responsible for translation, encryption and data compression

Application layer is responsible for providing access to the network

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Summary - IV

Performance, reliability and security are the network selection criterion which enables to choose efficient network

Standards organizations like ISO and ANSI develop technical and non- technical standards

International standards organizations are International Standard Organization (ISO), International Telecommunication Union (ITU), Institute of Electrical and Electronics Engineers (IEEE) and American National Standards Institute (ANSI)