chapter-1(topology).ppt

7/29/2019 Chapter-1(topology).ppt

1/35

Chapter - 1


2/35

What to be covered

Introduction to Computer Network

Components of Data Communication

Types of Data Flow

Types of Connection

Topologies

Categories of Network

Protocols and Standards


3/35

Evolution of Computer Network


4/35

What is ?

Communication

Information transfer, according to agreed conventions usinghand signals, language etc.

Telecommunication

Communicating at a distance, includes telephony, telegraphy,television etc.

Data Communication Transfer of data from one or more sources to one or more

destinations.

Computer Network Computer network means a collection of interconnected

computers(nodes). Computers(nodes) are said to be

interconnected if they can exchange information.


5/35

Delivery

Accuracy

Timeliness`

Jitter

Effectiveness of Data Communications system

depends on four fundamental character istics:


6/35

Data Communication

Components

Data Flow


7/35

F ive components of data communication

The data

(information) to be

communicated

The device that sends

data message

The device that

receives data message

The physical

path by which a

message travels

A Set of rules that

govern data

communication


8/35

Data F low

Simplex


9/35

Data F low contd..

Half-duplex


10/35

Data Flow contd

Full-duplex


11/35

Networks

Distributed Processing

Network Criteria

Physical Structures

Categories of Networks


12/35

Distr ibuted Processing

A task is divided among multiple computers.


13/35

Network Criter ia

Performance

Reliability

Security

Transit time

Response timeNo. of users

Type of transmission Medium

Frequency of failure

Time it taken to recover from failure

Protecting data from unauthorized

accessProtecting data from damage


14/35

Types of Connection

Point-to-Point Connection


15/35

Types of Connection Contd.

Multipoint Connection


16/35

Categories of topology


17/35

Mesh topology

Key Characteristics:

Fully Connected

Robust

Not flexible

Poor expandability


18/35

Mesh topology contd..

Every device has dedicated point-to-point link to every other device.

(n(n-1))/2 physical channels are required to linkn

devices.

Advantages:

No Traffic The use of dedicated link guarantees that each

connection can carry its data load, thus eliminate traffic problems.

Robust If one link becomes unusable, it does not affect the others.

Privacy/ Security Every message travels along a dedicated link,

hence only the intended recipient sees it.

Fault identification and fault isolation is easy.

Disadvantages:

Installation and reconfiguration is difficult.

The sheer bulk of wiring can be greater than the available space.

The hardware required to connect each link are expensive.


19/35

Star topology

Key features:

High Speed

Very Flexible

Robustness

High Maintainability


20/35

Star topology

Advantages:

Less expensive than mesh topology.

Easy to install and configure.

Less cabling required as compared to mesh.

Robust

Disadvantages:

More cabling required to bus or ring topology.

Central controller required.

If central device is down, the whole system is down.


21/35

Bus topology


22/35

Bus topology contd..

It uses multipoint configuration.

Advantages:

Ease of installation.

Backbone cable can be laid along the most efficient path.

Less cabling required.

Disadvantages:

Difficult reconfiguration and fault isolation.

Signal reflection at the taps can cause degradation in quality.

A fault or break in the bus cable stops transmission.


23/35

Ring topology


24/35

Ring topology contd..

Each device has a dedicated point-to-point line configurationonly with the two devices on other side of it.

Advantages:

Relatively easy to install and configure.

Disadvantages:

Unidirectional traffic can be a disadvantage.

A break in the ring can disable the entire network.


25/35

Categor ies of networks

A Network is categorized with respect to its size, its ownership

and the distance it covers.


26/35

LAN

Smaller scope

Building or small campus

Usually owned by same organization as attached

devices

Data rates much higherUsually broadcast systems


27/35

LAN (Continued)


28/35

MAN

Middle ground between LAN and WAN

May be owned by Private company or a service

provided by a public company

Large area


29/35

WAN

It provides long-distance transmission of information over large geographical

areas that may comprise a country, continent or even the whole world.

In contrast to LAN, WAN may utilize public, leased or private communication

devices, usually in combinations.


30/35

What is a Protocol

It is a set of rules that governs data communication.

A protocol defines what is communicated, how it is

communicated, and when it is communicated.

The protocol determines the following:

The type of error checking to be used Data compression method, if any

How the sending device will indicate that ithas finished sending a message

How the receiving device will indicate that it

has received a message


31/35

Key Elements of a Protocol

Syntax

Semantics

Timing

It refers to the structure or format of the

data, meaning the order in which they are

presented.For example, a simple protocol might expect

the first 8 bits of data to be the senders

address, the second 8 bits to be the

receivers address and the rest of the stream

to be the message itself.

It refers to the meaning of each section of

bits. How is a particular pattern to be

interpreted, and what action is to be taken

based on that interpretation?

For example, address identify the route to be

taken or final destination.

It refers when data should be sent and how

fast they can be sent .

For example , if a sender produces data at

100Mbps, but the receiver can process data

at only 1Mbps.

S D fi i i


32/35

Some Defini tion

internet : A collection of networks connected by internetworking

devices such as routers or gateways. A common form of internet is a

collection of LANs connected by a WAN. It is also known as

internetwork.

Internet (uppercase I): A global internet based on the TCP/IParchitecture, connecting millions of hosts worldwide.

Intranet : An intranet is a private network that is contained with an

enterprise. It may consists of many interlinked LAN and also useleased lines in the WAN. The main purpose of intranet is to share

company information and computing resources among employees.

A li ti


33/35

Application

Initially, computer network was developed for defense purpose, to

have a secure communication network.

After a decade or so, companies, in various fields, started using

computer networks for keeping track of inventories, monitor

productivity, communication between their different branch officeslocated at different locations.

And now after almost two decades, computer networks have

entered a new dimension; they are now an integral part of thesociety and people. In 1990s, computer network started delivering

services to private individuals at home.

S f th A li ti


34/35

Some of the Applications

Marketing and Sales

Financial Services

Manufacturing

Directory Services

Information Services

Electronic Data Exchange

Electronic Mail

Teleconferencing

Voice over IP

Video on Demand


35/35

The main area of applications can be broadly classified into followingcategories:

Scientific and Technical Computing

Client-Server model, Distributed Processing, Parallel Processing,

Communication Media

Commercial

Advertisement, Telemarketing, Teleconferencing

Network for the People

Telemedicine, Distance Education, Access to remote Information,Person to Person Communication, Interactive Entertainment

chapter-1(topology).ppt

Documents