17(1 Related) Cominication System

8/9/2019 17(1 Related) Cominication System

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Computer Communications and

Networking

S. D. PATIL

Deputy Director

PSTI


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Why it is LAN ?

Simple and inexpensive connections

Support for multiple media protocols

Flexibility to provide any-to-any

connections

Support for new applications

Ability to grow easily


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Computer Communication

LAN (Local Area Network)

WAN (

Wide Area Network)

Internet

Intranet


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LAN stands forLocal Area Network. A LAN is acommunications system that allows users to access

and share resources (computers, printers, servers)with other users.

LANs provide to share resources and information.They are simple, inexpensive, and support many

types of protocols. Other features include the ability to handle

connections to different types of network equipment and to support many applications. In

addition, LANs can be easily extended to allowfor changes in the number of users for anorganization that is expanding.


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How far is local?

Normally what limits the distance a LAN can

travel is the type of cable used.

The most common type of cable is unshielded

twisted pair (UTP), which is similar to the

round telephone wire found in your home.

UTP can carry signals up to 100 meters withouttoo much trouble. Other types of cable can carry

signals for longer distances.


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About LAN

It is defined as interconnection between two

different computers

It requires both H/W and S/W

H/W consists of cables and interfaces

S/W

consists of Management of the filesand communication systems.


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Advantages of LAN

To share expensive resources

to provide security for programs and data

expand PC usage

distributed processing

electronic mail data base management

S/W cost saving


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Every LAN System Provides

Compatibility

Internetworking

It provides Sharing of data

files,programs,electronic mail,peripherals

like printer,plotter.

Disk storage


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Hardware Components

File Server

Personal Computer

Or Nodes

NIC ( Network Interface Card)

Co-axial Cable

Connector (RJ-45)


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What Is a Topology?

The topology of a network refers to the way

in which all of its pieces have been

connected. That is, it refers to the layout of

the computers, printers, and other equipment

hooked to the network in the building

Network's topology is also a function of theway in which the cabling is organized


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Type of LAN Network Topology

Linear Bus topology Ring topology

Star topology

Tree topology Mesh topology


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Linear Bus

Linear Bus networks use a

common backbone

to connect all devices.

A single cable, the

Backbone functions as a shared communication medium, that

devices attach ortap into with an interface connector.


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Advantage and DisadvantageAdvantage:

The bus topology is very reliable, because if

any node on the busnetworkfails, the busitselfis NOT affected, and the remaining nodes cancontinue to operate without interruption.

Disadvantage:

The bus topology is that generally there mustbe a minimum distance between workstationsto avoid signal interference.


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Ring

In a ring network, every device

has exactly two neighbors for

communication purposes.

All messages travel through a

ring in the same direction

(effectively either "clockwise" or "counterclockwise"). A failure

in any cable or device breaks the loop and can take down theentire network.


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Advantage and Disadvantage Advantage:

Not appreciated.

Disadvantage:

- If one of the system fails, complete system collapse.

- Ring topologies is the extreme difficulty of adding new workstations

while the network is in operation. Normally, the entire network has to

be brought down while a new node is added and cabling reattached.


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StarMany home networks use the

star topology. A star network

features a central connection

point called a "hub" that may

be an actual hub or aswitch.

Devices typically connect to the hub with Unshielded Twisted

Pair (UTP) Ethernet.


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Advantage and Disadvantage Advantage:

The network administrator can give selected nodes a higher priority

status than others. The central computer looks for signals from thesehigher priority workstations before recognizing other nodes. Also, the

star topology permits centralized diagnostics (troubleshooting) of all

functions.

Disadvantage:

Of all the topologies, the star is the least reliable because it has a singlepoint of failure. The network relies mainly on the central computer for

all functions. If it fails, all nodes also stop functioning, resulting in

failure of the entire network.


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Tree(Distributed Star Network)

Tree topologies integrate multiple star topologies together

onto a bus.

In its simplest form, only hub devices connect directly tothe tree bus, and each hub functions as the "root" of a tree

of devices.

This bus/star hybrid approach supports future

expandability of the network much better than a bus

(limited in the number of devices due to the broadcast

traffic it generates) or a star (limited by the number of hub

ports) alone.


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Mesh topologies involve the concept ofroutes.

Unlike each of the previous topologies, messages sent on a

mesh network can take any of several possible paths fromsource to destination. (Recall that in a ring, although two

cable paths exist, messages can only travel in one

direction.) Some WANs, like the internet, employ mesh

routing

Mesh


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Any-to-Any ConnectivityInteroperability is the goal of any mixed-vendor network.

The Institute of Electrical and Electronics Engineers (IEEE) has

developed a set of 100 or so documents called IEEE 802.x

spec

ificat

io

nsw

hic

hde

fine ma

ny a

spect

so

fLAN operat

io

ns.

The Internet Engineering Task Force (IETF) has issued thousands

of Requests For Comments (RFC) that identify interoperability

problems and offer technical solutions.

The International Organization for Standardization (ISO) has

defined a communications framework known as the Open Systems

Interconnection (OSI) model, which divides LAN functions into

several layers of protocol.

While the OSI model is no longer a defacto industry standard, it

remains useful as a tool for identifying the function of new

protocols.


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O

SI model The Open System Interconnection (OSI)reference model was released in 1984 by theISO

It provided vendors with a set of standardsthat ensured greater compatibility andinteroperability among various networktechnologies produced by companies around

the world. Considered the best tool for teaching people

about sending and receiving data on anetwork.


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O

SI layers The OSI model explains how packets travelthrough the various layers to another device on anetwork:

It breaks network communication into smaller, more

manageable parts. It standardizes network components to allow multiple

vendor development and support.

It allows different types of network hardware andsoftware to communicate with each other.

It prevents changes in one layer from affecting otherlayers.

It divides network communication into smaller parts tomake learning it easier to understand


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O

SI Model


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Seven Layer Architecture

Physical Layer

Data link Layer

Network Layer

Session Layer

Transport Layer Presentation Layer

Application Layer


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F

unction of each layer

1 Physical layer

Cabling standard

2 Data link layer

Data in to Frames,Packets and control

Information.3Network layer

Concern with packet switching.


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4 Transport layer

Error recognition and recovery as well asmultiplexing of messages.

Regulation of information flow

5 Session layer

Password recognition, n/w monitoring and n/wmanagement functions.

6 Presentation layer

File transfer, n/w security

7 Application layer Electronic mail,Database Managers.


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Message Transmission Using Layers

Applications Applications

sender receiver

A receiving layer

wraps incoming

message with an

envelope

Adds layerrelated

addressing

information

A receiving layer

removes the

layer relatedenvelope and

forwards the

message up


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Data

Encoded

Logs on to remotemachine

AcknowledgmentEn co ded

Client Application Server Application

E n c o de d

Frames

En co ded

dNetwork packets

Transport packets

Application

Presentation

Transport

Physical

Data Link

Network

Session

Application

Presentation

Transport

Physical

Data Link

Network

Session

Data

Encoded

En co ded

E n c o de d

En co ded

d

Fig. OSI 7 layer model


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TCP/IP model The U.S. DoD created the TCP/IP reference model, becauseit wanted to design a network that could survive any

conditions, including a nuclear war.

TCP/IP was developed as an open standard


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TCP/IP IP can be thought to point the way for the packets,

while TCP provides a reliable transport

TCP is a connection-oriented protocol. It maintains

a dialogue between source and destination


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TCP/IP model

Handles issues of representation, encoding, and dialog

control

Handles quality of service issues of reliability, flow control,

and error correction.

Divides TCP segments into packets and send them from any

network. Best path determination and packet switching

host-to-network layer, concerned with all of the

components, both physical and logical, that are required to

make a physical link.


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Function of TCP/IP

It provides

Remote Logins

RemoteF

ile Transfer Electronic Mail

It handles

Error in transmission

Routing of information

Delivery of data


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TELNET= Remote Login

FTP=File Transfer Protocol

SMTP= Simple Mail Transfer Protocol

X = X windows System

Kerberose = Security

DNS = Domain Name System

ASN = Abstract Syntax Notation

SNMP = Simple Network Management ProtocolNFS = NetworkFile Server

RPC = Remote Procedure Calls

TFTP = TrivialFile Transfer Protocol

TCP = Transmission Control Protocol

UDP = User Data gram ProtocolIP = Internet Protocol

ICMP = Internet Control Message Protocol


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Telnet = Provides Remote Login capability

FTP = Enables to copy file from one system to another

SMTP = Use for transferring electronic mail

Kerberose = It is widely supported security protocol, it uses

application called Authentication Server to

validate Password.

DNS = Enables a computer with a common name to be

converted to a unique physical address.

SNMP = Provides status messages and problem report

across a network to an administrators.


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SNMP uses UDP as a transport Mechanism

NFS = Is a set of Protocols to enable multiple machines to

access each others directory transparently.

RPC = It is a set of functions that enable an application to

Communicate with another machine ( the server).It also provides programming functions,return codes

and predefined variables to support Distributed

Computing.

TFTP = It is simple protocol that lacks security.

It uses UDP as a transport. It perform same task asFTP but uses different transport protocol.

TCP = It provides reliable transfer of data.


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UDP = It is connectionless-oriented protocol meaning that it

does not provide for retransmission of data

gram(Unlike TCP, which is connection- oriented)

IP = Responsible for moving the packets of data assembled

by either TCP or UDP across network.

It uses a set of unique addresses for every device onthe network to determine routing and destination.

ICMP = ( Internet Control Message Protocol)

Responsible for checking and generating messages

on the status of devices on n/w.It can be used to inform other devices of a failure in

one particular machine.

ICMP & IP usually work together.


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Similarities:Similarities: both have layersboth have layers

both have applicationboth have applicationlayers, though theylayers, though they

include very differentinclude very differentservicesservices

both have comparableboth have comparabletransport and networktransport and networklayerslayers

packetpacket--switchedswitchedtechnology is assumedtechnology is assumed

networkingnetworkingprofessionals need toprofessionals need toknow bothknow both

Comparing TCP/IP with OSIComparing TCP/IP with OSI


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Comparing TCP/IP withOSI

Differences: TCP/IP combines the presentation

and session layer into its

application layer

TCP/IP combines the OSI data link

and physical layers

TCP/IP has fewer layers

TCP/IP protocols are the standards

around which the Internet

developed, so the TCP/IP model

gains credibility just because of itsprotocols. Networks aren't built on

the OSI protocol, even though the

OSI model is used as a guide.


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Peer-to-peer communications

For data to travel from the source to the destination,each layer of the OSI model at the source mustcommunicate with its peer layer at the destination.This is calledpeer-to-peercommunication

The protocols of each layer exchange information,called protocol data units (PDUs)

Each layer depends on the service function of theOSI layer below it. Ex:

Transport layer deals with segmentsNetwork layer encapsulates segments into packets

Data Link layer encapsulates packets into frames

Physical layer converts frames to bit streams


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Peer-to-peer communications


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Conversion steps to encapsulate

Data

Build the data

Package the data for end-to-end transport

Add the network IP address to the header

Add the data link layer header and trailer

Convert to bits for transmission


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Detailed encapsulation process

If one computer (host A) wants to send data toanother computer (host B), the data is packaged

through a process called encapsulation

As the data packet moves down through the layers of

the OSI model, it receives headers, trailers, and otherinformation.


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Encapsulation


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Modem Modem

Telephone L ineTelephone L ine


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What is a Wide Area Network? Links Different Locations

within YourOwn Organization

Similar to LAN but slower and

over greater distances

Can be Virtual (use Internet to

create VPN)

Bridge between two or more

LANs

ServerPC PCPCPrinter

Server

PC PCPC Printer


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What are Hubs?

A hub is the active elementwhich turns a collection of

wires into a network. It is the hub of a network. Most

common for modern networks is a Star Topology


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What are Switches? A switch is an active element much like a hub. However, the

entire bandwidth is available on every port, rather than

being shared among the ports. Think of a hub as a party-

line phone, whereas a switch represents Direct-inbound-dial.

A 24-port 10/100

Mbs switch is

nominally

24 x 10 x 2 faster

than a 24-port

10BaseThub


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NetworkingandInternetworking

Devices, Backbone

Networks


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Hubs andRouters

What is a hub?

A hub acts as a multiport repeater

anything it receives on one port is repeated to all other ports

the network is analogous to a party line

What is a router?

A router acts as a traffic cop. Each message is only broadcast over

the network segment that it has permission to travel over.

A router allows you to segment the network, this reduces the

number of devices on a network segment


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What are Routers? A router is a specialized, dedicated device for connecting

local area networks together into internets (e.g., from

Ethernet LAN to T1 WAN). It sends each packet of data

to the right location.

To The InternetTo Accounting

To Sales


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Networking devices are used to construct networks.

Example: A local area Network (LAN) may need to cover more

distance that its media can handle effectively. In this case, you

can use a repeater to regenerate the signal.


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Internetworking devices are used to connect networks.

Example: If you want to link a LAN into an internet, you

need an internetworking device as a Router or a

Gateway.

An internet is an interconnection of individual networks.


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Connecting Devices and the OSIModel


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Connecting Devices


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Connecting DevicesConnecting Devices

Repeaters

Hubs

Bridges

Two-Layer Switches

C ti d i


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Connecting devices


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Repeaters

A repeater (or regenerator) is an electronic device thatoperates on only the physical layer of the OSI model.

A repeater installed on a link receives the signal before it

becomes too weak or corrupted, regenerates the original

pattern, and puts the refreshed copy back on the link.


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Repeaters

A repeater does not actually connect two LANS; it connectstwo segments of the same LAN.

A repeater forwards every frame; it has no filtering capability.


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Bridges

Bridgesoperate in both the physical and the data linklayers of the OSI model.


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Bridges

Bridges can divide a large network into smaller segments. Theycontain logic that allows them to keep the traffic on each segment

separate. When a frame (or packet) enters a bridge, the bridge not only

regenerates the signal but checks the destination address and forwards

the new copy only to the segment the address belong.


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Bridges

A bridge operates in both the physical and the data link layers.

As a physical layer device, it regenerates the signal it receives.

As a data link layer device, the bridge can check the physical

address (source and destination) contained in the frame.

A bridge has filtering capability. It can check the destination

address of a frame and decide if the frame should beforwarded or dropped. If the frame is to be forwarded, the

decision must specify the port.

A bridge does not change the physical addresses in a frame.

A bridge has a table used in filtering decisions.

B id


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Bridge


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ypes of Bridges

To select between segments, a bridge must have a look-uptable that contains the physical addresses of every stationconnect to it. The table indicate to which segment eachstation belongs.

Simple Bridge

The address table must be entered manually, before asimple bridge can be used.

Whenever a new station is added or removed, the tablemust modified.

Installation and maintenance of simple bridges are time-consuming and potentially more trouble than the costsavings are worth.


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Types of Bridges

Multiport bridgesA multiport bridge can be used to connect more than two

LANs.


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Types of Bridges

Transparent Bridge

A transparent, or learning, bridge builds its table of station

addresses on its own as it performs its bridge functions.

T B d


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Transparent Bridges

A transparentbridge is a bridge in which the stations are

completely unaware of the bridges existence.

If a transparentbridge is added or removed from the

system, reconfiguration of the stations is unnecessary.

A transparent bridge must meet three criteria:

1. Frames must be forwarded from one station to another.

2. The forwarding table is automatically made by learning framemovements in the network.


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Learning Bridge


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Loop Problem

Transparent bridges work fine as long as there are no

redundant bridges in the system.

Bridges are normally installed redundantly, which means that

two LANs may be connected by more than one bridge. In this

case, if the bridges are transparent bridges, the y may create a

loop, which means a packet may be going round and round,from one LAN to another and back again to the first LAN.

See next slide

To solve the looping problem, the IEEE specification requires

that bridges use the spanning tree algorithm to create aloopless topology.

Loop problem


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Loop problem


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Spanning Tree A spanning tree is a graph in which there is no

loop.

In a bridged LAN, a loopless topology means a

topology in which each LAN can be reached from

any other LAN through one path only (no loop).

It is not possible to change the physical topology

of the system, but we can create a logical topology

that overlays the physical one.


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Source Routing

Another solution to prevent loops in LANs connected by

bridges is source routing. In this method, the source of the

packet defines the bridges and the LANs through which the

packet should go before reaching the destination.


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Routers

Routers have accessto network layer

addresses and contain

software that enables

them to determine

which of several

possible paths

between those

addresses is the best

for a particular

transmission.

Routers operate in thephysical, data link,

and network layers of

the OSI model.


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Routers relay packets among multiple interconnected

networks. They route packets from one network to any of a

number of potential destination networks on an internet.


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Gateways

Gateways potentially operate in all seven layers of the

OSI

model.


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Gateways

A gateway is a protocol converter. A router by itselftransfers, accepts, and relays packets only across networks

using similar protocols.

A gateway can accept a packet formatted for one protocol

(e.g. AppleTalk) and convert it to a packet for anotherprotocol (e.g. TCP/IP).


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Gateways

A gateway is generally software installed within a router.The gateway understands the protocols used by each

network linked into the router and is therefore able to

translate from one to another.


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Backbone Networks

A backbone network allows several LANs to be

connected.

In a backbone network, no station is directly connected tothe backbone; the stations are part of a LAN, and the

backbone connects the LANs.

The backbone itself is a LAN.

The two most common architectures are the bus backboneand the star backbone.

Bus backbone


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BusBackbone

In a bus backbone, the topology of the backbone is a bus.

Bus backbones are normally used as a distributionbackbone to connect different buildings in an organization.

Star Backbone

In a star backbone, the topology of the backbone is a star;the backbone is just a switch.

Star backbones are mostly used as a distribution backbone

inside a building.

In a multifloor building usually there is a LAN that serveseach particular floor. A star backbone connects these

LANs.

Star backbone


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PhysicalWiring Diagram


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History ofWWW

In 1980, Web was initially conceived at

CERN .

A man name Tim Berners-lee first to

submit its proposal in 1989

The first WWW computers were created at

CERN (http://www.cern.ch)

It works on the principle of Server and

Client.


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About Internet Connection

By using Modem and Telephone Line

By using ISDN


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B P A S Y S T E M

GenerationCorps of EngineersBureau of Reclamation

Supply System

Transmission

Substation

Distribution

Ultimate Customersof Electricity

Residential

Commercial

Farm

Government


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Thank You

By

SANJAY D. PATIL

AssistantDirectorNPTI

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17(1 Related) Cominication System