Lec01-Intro to Networking

8/2/2019 Lec01-Intro to Networking

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Networking Concepts

Introductory Lecture

By

Mushhad Gilani


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Books & study Material

Text Book:-

Data Communication and Networking,

4/e. Author: Behrouz A. Forouzan

Reference Books/Material

Larry L. Peterson and Bruce S. Davies [2000],

Computer Networks A Systems Approach,Second Edition


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Introduction Meaning:

Networking consists oftwo or more than two computersconnected to each other by a medium(cable) so that they can share a data.

Definition:A group of computers and

other devices connected together iscalled a network and the concept of

connected computers sharing resourcesis called as Network.


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Uses of Computer Networks

Network for Companies

Network for People.

Social Issues


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Network for Companies.

Many Organizations have asubstantial number of computersin operation, often located farapart The goal are Resources Sharing

High reliability

Saving money

Scalability


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Network for People.

Starting in 1990s, computernetworks began to startdelivering services to privateindividuals at home. Below wedescribe some services. Access to remote information.

Person to person communication


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Social Issues

On the other hand Thewidespread introduction ofNetworking will introduce new

social, ethical, political problems.


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1-1 DATA COMMUNICATIONS

The termtelecommunication means communication at a

distance. The worddata refers to information presentedin whatever form is agreed upon by the parties creating

and using the data. Data communications are the

exchange of data between two devices via some form of

transmission medium such as a wire cable.

Components

Data Representation

Data Flow

Topics discussed in this section:


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Figure 1.1 Five components of data communication

MessageSenderReceiver

MediumProtocol


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Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)


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Figure 1.3 Types of connections: point-to-point and multipoint


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Explanation:

Networking arose from the needto share data in timely fashion.Computers in a network canshare:

a) Data

(b) Messages

(c) Graphics

(d) Printers

(e) Modems.


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How Data Communication took Place


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Types of Networks

There are three different ways inwhich we classify the networks

1) Organizational Point of View

2) Geographical Point of View

3) Computing Point of View


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Organizational Point of

ViewFrom organizational point of view,

networks are divided into twotypes

Peer-to-Peer

Server based


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Peer-to-Peer These are also called

Workgroups.

A peer-to-peer network comprisesof 10 or less users and is suitable

for small-sized businessorganizations.

In this model of networking the

resources are randomly scatteredon the network with everymachine acting as a server as well

as client


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Server Based networks

They are sometimes referred to asDomains.This is a centralized model of networkingwith resources placed on a dedicatedmachine called Server.There is no user limit as such, as itdepends directly on your hardware

resources and capacity to support users.


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Geographical Point of View

From geographical point of view,there are three types ofnetworks.

LAN

WAN

MAN/CAN


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Classification of GeographicalNetworks by Scale


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LAN or Local Area Network

A LAN encompasses a smallarea such as a floor or abuilding with all themachines connected directlyvia the same mediumgenerally.


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Examples: LAN

Two networks: (a) Bus (b) Ring


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Local Area Network


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Local Area Network


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WAN or Wide Area Network

A WAN comprises of a very largephysical area that covers countries

and continents. Internet is onegood example of a WAN. Themachines in a WAN are connectedthrough different mediums andprotocols. Generally, the Dial-up-Networks are used for thispurpose.


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Wide Area Network


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Internet MAP

This map of the Internet appeared in the December 1998 Wired.


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MAN (Metropolitan Area Network)or

CAN (Campus Area Network)A MAN is almost similar to a WANthat a MAN only encompasses anarea that is within a city.CAN is a campus area Networkwhich is used with in a campus forthe sharing of resources.


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Example: MAN

A metropolitan area network based on

cable TV


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Metropolitan Area Network


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Internetwork

(Internet)


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Computing Point of View

Networks are divided intotwo types from the point

of view of computing.

1.Centralized Networks

2.Client-Server Networks


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Centralized Networks

The centralized networksrelytotally on one dedicated machinecalled server for all the processingand computing and the clients or

the terminals act as dumb entities. If the client requires a certain set

of data, whole of the data set istransferred at the client end, which

also is wastage of the networkbandwidth.


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Client-Server Networks In this model of networking, only

the required set of data is returnedto the client while both the server

and the client take part in theprocessing or computing of thequeries.

This is a more efficient way ofprocessing and is hence appliedgenerally more than thecentralized method, nowadays. .


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Topology

A topology is the physical layoutor design of the networks thatspecifies the cabling method as

well as the arrangement of thecomputers.

It also explains the access

method used by the computersthat represent that topology.


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Types of Topology

There are following types oftopologies, generally:

Bus Topology

Star TopologyRing Topology

Mash Topology


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Bus Topology The bus topology consists of a long linear cable

also called trunk or linear trunk or backbone. In this type of topology, all the computers are

connected to this main cable. Bus is a passivetopology. The main features of the bustopology are discussed as under:

Signal BouncingThis is a phenomena observed in this type oftopology.

In signal bouncing, the data signal travels acrossthe cable medium from one end to another and

if not absorbed at the other end, it will keep onbouncing back and forth across the medium andtherefore will stop any further communicationon the network. This is called signal bouncing.


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Bus Topology


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Terminator:In order to avoid signal bouncing, a device called terminatoris used at one end of the medium that absorbs the signal and

hence restricts it from affecting the overall networkcommunication. It could be a grounding method as well withone end grounded into a wall socket.Signal Attenuation:After the data travels a long distance on the cable , itstarts becoming weaker and weaker until it reaches a pointwhere it cannot be received in the correct form. Thisprocess is called Signal Attenuation.Repeater:

The solution to Signal Attenuation is a device called repeaterthat regenerates or amplifies the signal to make it strongenough to be received correctly at the destination end


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Star Topology

In star topology there is a centralnetwork traffic managementdevice called hub/Switch.

All the nodes (computers)are

connected directly to the hubandare thereby interconnected witheach other.

Star topology does not allowdirect traffic.


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Star Topology


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Tree Topology


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ADVANTAGES

Easily Expanded

Easier to Troubleshoot

Multiple cable types Supported byhubs


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DISADVANTAGES

Hub failure

Requires more Cable

May require a device to re broad castsignals across the network

Ri T l


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Ring Topology In ring topology the computers connected

with each other via a single cable runconstitute a logical ring.

Ring is an active topology and also thatevery computer on the ring acts as arepeater i.e., it regenerates the signal andtransmits it onto the cable.

Token PassingA frame or sequence of data called token

passes from one computer to another onthe ring and makes the networkcommunication possible in a way that onlythe computer with token has theopportunity to transmit data on the ring.Here is how the process works: (TokenTravling on the ring.swf)
http://../figures/Token%20Travling%20on%20the%20ring.swfhttp://../figures/Token%20Travling%20on%20the%20ring.swfhttp://../figures/Token%20Travling%20on%20the%20ring.swfhttp://../figures/Token%20Travling%20on%20the%20ring.swfhttp://../figures/Token%20Travling%20on%20the%20ring.swfhttp://../figures/Token%20Travling%20on%20the%20ring.swf


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ADVANTAGES

It provides an orderly network inwhich every device has access to thetaken and can transmit

It performs well under a heavenload.


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DISADVANTAGES

Malfunctioning workstation andcables create problems for the entirenetwork

Changes made when adding orremoving a device affect the entirenetwork.


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Ring Topology


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MESH

The mesh topology provides thehighest level of fault tolerance. Ituses separate cables to connect each

device to every other device on thenetwork, providing a StraightCommunication path.

Dedicated point to point link.


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Mesh Topology


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Hybrid Topology


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A hybrid topology: a star backbone with three bus networks


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Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet


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Figure 1.11 WANs: a switched WAN and a point-to-point WAN

Figure 1 12 A h t t k d f f WAN d t LAN


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Figure 1.12 A heterogeneous network made of four WANs and two LANs

Active Topology Vs Passive


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Active Topology Vs PassiveTopology

The difference between active topology and

the passive topology is that in an activetopology the computers are themselvesresponsible for the successful transference ofdata while in a passive topology this is not thecase.

Example: In star or the bus topology, if a computer fails,

this does not affect the whole network and thecommunications on the network still go on.While in case of a ring topology, if even a

single computer goes down, the wholenetwork comes to a state of being down as thetoken gets stuck into that computer andthereby stopping all the networkcommunication

Lec01-Intro to Networking

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