Internet and Internet and wwwwww

InternetInternet A loosely configured global wide-area A loosely configured global wide-area

network.network. Includes more than 31,000 different Includes more than 31,000 different

networks innetworks in over 100 different countries.over 100 different countries.

Millions of people visit and contribute to the Millions of people visit and contribute to the Internet, through e-mail and the World WideInternet, through e-mail and the World Wide Web.Web.

Began as a Department of Defense project.Began as a Department of Defense project. For detailed information about the history of For detailed information about the history of

thethe Internet, see:Internet, see: http://dir.yahoo.com/Computers_and_internet/Intehttp://dir.yahoo.com/Computers_and_internet/Inte

rnet/History/rnet/History/

InternetInternet

An interconnected network of An interconnected network of thousands of networks and millions of thousands of networks and millions of computers linking business, computers linking business, educational institutions, government educational institutions, government agencies and individuals together.agencies and individuals together.

The largest collection of networks in The largest collection of networks in the world, interconnected to allow the world, interconnected to allow them to function as a single virtual them to function as a single virtual network network

Early history of InternetEarly history of Internet In the 1950s the U.S. Department of DefenseIn the 1950s the U.S. Department of Defense

became concerned that a nuclear attack couldbecame concerned that a nuclear attack could disable its computing (and thus planning anddisable its computing (and thus planning and coordinating) capabilities. coordinating) capabilities.

By 1969 the Advanced Research Projects AgencyBy 1969 the Advanced Research Projects Agency Network (ARPANet) had been constructed.Network (ARPANet) had been constructed.

The first computers to be connected were ones The first computers to be connected were ones atat the University of California at Los Angeles, SRIthe University of California at Los Angeles, SRI International, the University of California atInternational, the University of California at Santa Barbara, and the University of Utah.Santa Barbara, and the University of Utah.

Terminology Terminology A A hypertext serverhypertext server is a computer that stores files is a computer that stores files

written in hypertext markup language (HTML)written in hypertext markup language (HTML) and lets other computers connect to it and readand lets other computers connect to it and read those files. It is now called a those files. It is now called a Web serverWeb server..

A A hyperlinkhyperlink is a special tag that contains a is a special tag that contains a pointerpointer to another location in the same or in a differentto another location in the same or in a different HTML document.HTML document.

HTML is based on Standard Generalized MarkupHTML is based on Standard Generalized Markup Language (SGML), which organizations haveLanguage (SGML), which organizations have used for many years to manage large documentused for many years to manage large document filing systems.filing systems.

Local Area Network (LAN) Local Area Network (LAN)

A link-up of workstations and A link-up of workstations and peripheral equipment in an office, peripheral equipment in an office, building, or locality so users may building, or locality so users may communicate and share equipment communicate and share equipment and information. and information.

LAN lets you share the resources of LAN lets you share the resources of other computersother computers

LAN can be further characterized by LAN can be further characterized by topologytopology

MAN(Matropolian Area MAN(Matropolian Area Network)Network)

It is the network which covers a city.It is the network which covers a city. The best example of the MAN is The best example of the MAN is

Cable TV network which covers a Cable TV network which covers a city city

In today’s world High speed wireless In today’s world High speed wireless internet access is also a good internet access is also a good example of MAN.example of MAN.

WAN(Wide Area WAN(Wide Area Network)Network)

A WAN spans a large geographical A WAN spans a large geographical area such as a country or continent.area such as a country or continent.

It uses Hosts which are connected It uses Hosts which are connected by communicated subnets.by communicated subnets.

TopologyTopology

Topology describe the manner in Topology describe the manner in which various computer nodes are which various computer nodes are interconnected to each otherinterconnected to each other

In this context there are different In this context there are different topologies:topologies: BusBus RingRing Star Star MeshMesh TreeTree

Bus TopologyBus Topology Consists of nodes connected to a single bus Consists of nodes connected to a single bus

made up of a long cable.made up of a long cable. A thick coaxial cable may serve as the bus A thick coaxial cable may serve as the bus

and all computer nodes are connected to and all computer nodes are connected to this running coaxial cablethis running coaxial cable

The computer nodes directly receive and The computer nodes directly receive and inject data from the bus. Data traverses in inject data from the bus. Data traverses in both directionboth direction

One communication channel exists to serve One communication channel exists to serve the entire network.the entire network.

If this channel fails, then the whole If this channel fails, then the whole network will go out of operation.network will go out of operation.

Ring TopologyRing Topology

Nodes are organized to form a ring Nodes are organized to form a ring structurestructure

The first node is connected to second The first node is connected to second using linkusing link

Second is connected to third and so onSecond is connected to third and so on The last node is connected to first using The last node is connected to first using

point to point link.point to point link. Signals travel internally around the Signals travel internally around the

network from one node to othernetwork from one node to other

Star TopologyStar Topology Each computer node is connected to Each computer node is connected to

a central devicea central device Nodes are located at one end of the Nodes are located at one end of the

segment and other end is terminated segment and other end is terminated in a central device, usually a hub or in a central device, usually a hub or a switcha switch

Reliable topologyReliable topology If one node is down, others on If one node is down, others on

network are not affected.network are not affected.

Mesh topologyMesh topology

Multiple number of pathsMultiple number of paths Because of it reliability of the Because of it reliability of the

network improved.network improved. expensiveexpensive

Tree toplologyTree toplology

Structure like a treeStructure like a tree Reliable problem exists due to Reliable problem exists due to

control exercised by topmost node in control exercised by topmost node in the tree.the tree.

IP AddressIP Address

All the host connected to Internet All the host connected to Internet have an officially address.have an officially address.

It is 4 bytes long and written in It is 4 bytes long and written in dotted decimal notation.dotted decimal notation.

For example IP AddressFor example IP Address

10000001.1000000.00000100.00000110000001.1000000.00000100.00000101 can be written as 129.128.4.501 can be written as 129.128.4.5

IntranetIntranet

Intranet offers companies open Intranet offers companies open communication and information access, communication and information access, just like the internet but with the added just like the internet but with the added advantage of protection from the outside advantage of protection from the outside world by passwords, encryption and world by passwords, encryption and electronic barriers or firewalls. electronic barriers or firewalls.

An intranet is an internet network that is An intranet is an internet network that is located inside the organization and not located inside the organization and not generally accessible by the general generally accessible by the general public.public.

IntranetIntranet

To create our own intranet we need,To create our own intranet we need, A TCP/IP networkA TCP/IP network E-mail client s/wE-mail client s/w E-mail serverE-mail server Web serverWeb server A browserA browser ChatChat FTPFTP

Growth of IntranetsGrowth of Intranets

The spread of networked comp system The spread of networked comp system based on PC.based on PC.

The availability of TCP/IP on almost every The availability of TCP/IP on almost every computer platform, large and small.computer platform, large and small.

The wide adoption of open standards The wide adoption of open standards such as HTTP and HTML.such as HTTP and HTML.

The availability of low cost, high power The availability of low cost, high power web servers such as the internet web servers such as the internet information server.information server.

Advantages of IntranetAdvantages of Intranet

Web technologies scalable and Web technologies scalable and applied small and medium sized applied small and medium sized LAN.LAN.

Easy to use web browsers are Easy to use web browsers are available for virtually all operating available for virtually all operating system and h/w combinations. system and h/w combinations.

Advances in HTML authoring tools Advances in HTML authoring tools make it much easier to create HTML make it much easier to create HTML pages for web servers.pages for web servers.

Disadvantages of Disadvantages of IntranetIntranet

Intranet requires TCP/IP protocol Intranet requires TCP/IP protocol and may not work with your existing and may not work with your existing choices.choices.

HTML is not a development HTML is not a development language, we will have to use CGI or language, we will have to use CGI or Perl scripts, or even C or java Perl scripts, or even C or java programmes to access database programmes to access database systems.systems.

ExtranetExtranet

A network that links selected A network that links selected resources of the intranet of a resources of the intranet of a company with its customers, company with its customers, suppliers and other business suppliers and other business partners, using the internet or partners, using the internet or private networks to link the private networks to link the organizations intranets.organizations intranets.

TCP / IP LayersTCP / IP Layers

Network Interface LayerNetwork Interface Layer: : Responsible for placing packets on Responsible for placing packets on and receiving them from the network and receiving them from the network medium, which could be a local area medium, which could be a local area network (Ethernet) or Token Ring or network (Ethernet) or Token Ring or other network topology.other network topology.

Internet LayerInternet Layer: This layer is : This layer is responsible for addressing, packaging, responsible for addressing, packaging, and routing messages on the Internet.and routing messages on the Internet.

TCP / IP LayersTCP / IP Layers

Transport LayerTransport Layer: Responsible for : Responsible for providing communication with the providing communication with the application by acknowledging and application by acknowledging and sequencing the packets to and fro from sequencing the packets to and fro from the application.the application.

Application LayerApplication Layer: Provides a wide : Provides a wide variety of applications with the ability to variety of applications with the ability to access services of the lower layersaccess services of the lower layersSome of the best applications are Some of the best applications are FTP,SMTP and HTTPFTP,SMTP and HTTP

Internet Service ProviderInternet Service Provider

Firm that provides the lowest level Firm that provides the lowest level of service in the multi-tiered internet of service in the multi-tiered internet architecture by leasing internet architecture by leasing internet access to home owners, small access to home owners, small business, and some large business, and some large institutions.institutions.

Client Server ComputingClient Server Computing

A model of computing in which very A model of computing in which very powerful personal computer are powerful personal computer are connected together in a network connected together in a network with one or more servers.with one or more servers.

Internet is a giant example of client Internet is a giant example of client server computingserver computing

Client, ServerClient, Server

CLIENTCLIENT: A powerful personal computer : A powerful personal computer that is part of a network. That is capable that is part of a network. That is capable of displaying rich graphics storing large of displaying rich graphics storing large files and processing sound and graphic files and processing sound and graphic files.files.

SERVERSERVER:: Networked computer Networked computer dedicated to common functions that the dedicated to common functions that the client machines on the network need, client machines on the network need, such as storing files, software such as storing files, software applications, utility programs such as applications, utility programs such as web connections and printersweb connections and printers

Hyper Text Transfer Hyper Text Transfer ProtocolProtocol

The set of rules for exchanging files (text, The set of rules for exchanging files (text, graphic images, sound, video, and other graphic images, sound, video, and other multimedia files) on the World Wide Web. multimedia files) on the World Wide Web.

Runs in the application layer of the TCP/IP Runs in the application layer of the TCP/IP model. An HTTP session begins when a model. An HTTP session begins when a client’s browser requests a web page from client’s browser requests a web page from remote internet serverremote internet server

When the server responds by sending the When the server responds by sending the page requested, the HTTP session for that page requested, the HTTP session for that object endsobject ends

SMTP, IMAP, POPSMTP, IMAP, POP

SMTPSMTP: Internet protocol used to send : Internet protocol used to send mail to server (Simple Mail Transfer mail to server (Simple Mail Transfer Protocol)Protocol)

POPPOP: Post Office Protocol, a protocol : Post Office Protocol, a protocol used by the client to receive the mail from used by the client to receive the mail from an internet server.an internet server.

IMAPIMAP: a more current e-mail protocol : a more current e-mail protocol that allows users to search, organize, and that allows users to search, organize, and filter their mail prior to downloading it filter their mail prior to downloading it from the server (Internet Message Access from the server (Internet Message Access Protocol)Protocol)

FTPFTP Internet service that allow you to transfer Internet service that allow you to transfer

file from one computer to another file from one computer to another computer using client/server technologycomputer using client/server technology

You run a client program on your computer You run a client program on your computer which connects to a server program on a which connects to a server program on a remote computer remote computer

When you copy a file from remote server When you copy a file from remote server we say that you are downloading and when we say that you are downloading and when you copy a file from your computer to you copy a file from your computer to remote one you are uploading the fileremote one you are uploading the file

In FTP terminology your computer is In FTP terminology your computer is LOCAL HOST, the other computer is LOCAL HOST, the other computer is REMOTE HOSTREMOTE HOST

FTPFTP

SSLSSL SSL developed by Netscape SSL developed by Netscape

Communications Company, is a standard Communications Company, is a standard that encrypts data between a Web that encrypts data between a Web browser and a Web server. SSL does not browser and a Web server. SSL does not specify what data is sent or encrypted. In specify what data is sent or encrypted. In an SSL session, all data sent is encrypted.an SSL session, all data sent is encrypted.

It helps secure communications and It helps secure communications and payments through a variety of techniques payments through a variety of techniques such as message encryption and digital such as message encryption and digital signatures.signatures.

TelnetTelnet Telnet is a internet service that allow you to Telnet is a internet service that allow you to

log in to a remote internet computerlog in to a remote internet computer To utilize this service, you need a Telnet To utilize this service, you need a Telnet

client on your machine. Client uses internet to client on your machine. Client uses internet to connect to the remote computerconnect to the remote computer

Once the connection is made, the client acts Once the connection is made, the client acts as intermediary between remote and your as intermediary between remote and your computercomputer

Every thing you type on your machine is Every thing you type on your machine is passed on to the remote computerpassed on to the remote computer

Everything the other computer displays is Everything the other computer displays is sent to your computersent to your computer

TelnetTelnet

FingerFinger

Finding People on the Internet. You Finding People on the Internet. You can find out who is logged on to a can find out who is logged on to a remote network by using Telnet to remote network by using Telnet to connect to a server and then typing connect to a server and then typing fingerfinger at the prompt. at the prompt.

Finger can tell you who is logged in Finger can tell you who is logged in and how long they have been and how long they have been attached and their user nameattached and their user name

FingerFinger

PingPing

Testing address. You can ping a host Testing address. You can ping a host computer to check the connection computer to check the connection between your client and server. The between your client and server. The Ping will also tell you the time it Ping will also tell you the time it takes for the server to respond takes for the server to respond giving some idea of the internet giving some idea of the internet speed at that time (Packet Internet speed at that time (Packet Internet Groper)Groper)

Limitations of Internet ILimitations of Internet I BandwidthBandwidth: Slow service and a very limited : Slow service and a very limited

capacity to handle video and voice traffic.capacity to handle video and voice traffic. Quality of ServiceQuality of Service: Packets take circuitous : Packets take circuitous

root to reach destination. This results in root to reach destination. This results in latency. With streaming video and latency. With streaming video and synchronous communication, latency is synchronous communication, latency is noticeable and user perceives jerkiness in noticeable and user perceives jerkiness in movies and delay in voice communication. movies and delay in voice communication.

LatencyLatency: uneven flow of information : uneven flow of information packets throughout the networkpackets throughout the network

Limitations of Internet ILimitations of Internet I Network ArchitectureNetwork Architecture: A thousand requests : A thousand requests

for single music track from a central server for single music track from a central server will result in a thousand efforts by the server will result in a thousand efforts by the server to download the music to each requesting to download the music to each requesting client. This slows down network performance.client. This slows down network performance.

Language DevelopmentLanguage Development: HTML the : HTML the language of the web pages is fine for text and language of the web pages is fine for text and simple graphics but poor at defining rich simple graphics but poor at defining rich graphic and communicating “rich documents” graphic and communicating “rich documents” such as databases, business documents, or such as databases, business documents, or graphics.graphics.

World Wide WEBWorld Wide WEB

WWWWWW

Hypertext Hypertext It is a way of formatting pages with It is a way of formatting pages with

embedded links that connects documents to embedded links that connects documents to one another, and that also links pages to one another, and that also links pages to other objects such as sound, video, or other objects such as sound, video, or animation files.animation files.

When you type a web address in you browser When you type a web address in you browser such as such as http://www.imt.eduhttp://www.imt.edu, your browser , your browser sends an HTTP request to the imt.edu server sends an HTTP request to the imt.edu server requesting the home page of imt.edurequesting the home page of imt.edu

HTTP is the first set of letter at the start of HTTP is the first set of letter at the start of every web address followed by the domain every web address followed by the domain name.name.

Uniform Resource Uniform Resource LocatorLocator

The directory path and document The directory path and document name are two more pieces of name are two more pieces of information with the web address information with the web address that help the browser track down that help the browser track down the requested page.the requested page.

Together the address is called a Together the address is called a URL. When typed into a browser, a URL. When typed into a browser, a URL tells exactly where to look for URL tells exactly where to look for information. For example: information. For example: http://www.imt.edu/dlp/pgdbm.htmhttp://www.imt.edu/dlp/pgdbm.htm

Mark Up LanguagesMark Up Languages SGMLSGML: Standard Generalized Markup : Standard Generalized Markup

Language. The purpose of SGML was Language. The purpose of SGML was to help very large organizations to help very large organizations format and categorize large format and categorize large collection of documents.collection of documents.

It can run independent of any It can run independent of any software program, but it is extremely software program, but it is extremely completed and difficult to learn.completed and difficult to learn.

An early version of Generalized An early version of Generalized Markup languageMarkup language

Hypertext Mark-up Hypertext Mark-up LanguageLanguage

One of the next generation GML that One of the next generation GML that is relatively easy to use in the web is relatively easy to use in the web page design.page design.

HTML provides web page designers HTML provides web page designers with a fixed set of markup tags that with a fixed set of markup tags that are used to format a web page.are used to format a web page.

HTML functions to define the HTML functions to define the structure and style of a document, structure and style of a document, including the headings, graphic including the headings, graphic positioning tables and text formattingpositioning tables and text formatting

Extensible Markup Extensible Markup LanguageLanguage

XML is a new Markup language XML is a new Markup language specification developed by W3C. It is a specification developed by W3C. It is a Markup language like HTML but with Markup language like HTML but with a different purpose. XML is designed a different purpose. XML is designed to describe data and information.to describe data and information.

XML can be used to define database XML can be used to define database records and this will enable records and this will enable organizations to put most of their organizations to put most of their information processing functions into information processing functions into an Internet processing environmentan Internet processing environment

Web Server and ClientsWeb Server and Clients

Security servicesSecurity services FTPFTP Search engineSearch engine Data captureData capture

The Internet and The Internet and WEBWEBFeaturesFeatures

Electronic MailElectronic Mail The most used application of the The most used application of the

InternetInternet Uses a series of protocols to enable Uses a series of protocols to enable

messages containing text, images, messages containing text, images, sound and video clips to be sound and video clips to be transferred from one internet user to transferred from one internet user to anotheranother

AttachmentAttachment: A file inserted with in : A file inserted with in the e-mail message.the e-mail message.

SpamSpam: Unsolicited e-mail.: Unsolicited e-mail.

Search EnginesSearch Engines Identifies web pages that appear to Identifies web pages that appear to

match keywords, also called queries, match keywords, also called queries, typed by the user and provides a list typed by the user and provides a list of the best matches.of the best matches.

Top search Engines Yahoo, MSN, Top search Engines Yahoo, MSN, AOL, Lycos, Go, Netscape, NBCi, AOL, Lycos, Go, Netscape, NBCi, Exite, AskJeeves, Alta Vista, Google, Exite, AskJeeves, Alta Vista, Google, LookSmart, GoTo, Iwon, Direct Hit, LookSmart, GoTo, Iwon, Direct Hit, DogPileDogPile

Intelligent Intelligent AgentsAgents

Or Software Or Software Robots (bots) Robots (bots) are software are software programs that programs that gather and / or gather and / or filter filter information on information on specific topic specific topic and then and then provide a list of provide a list of results for the results for the user.user.

Search Search BotBot

Altivista.comAltivista.com

WebcrawlerWebcrawler

ShoppinShopping Botg Bot

MySimonMySimon

DealTimeDealTime

Update Update BotBot

UrlyWarningUrlyWarning

News News BotBot

WebClippingWebClipping

SportSpiderSportSpider

Chatter Chatter BotBot

eGaineGain

NativeMindsNativeMinds

Instant messagingInstant messaging

Displays word type on computer Displays word type on computer almost instantaneously. Recipients almost instantaneously. Recipients then can respond immediately to then can respond immediately to sender the same way, making the sender the same way, making the communication more like a live communication more like a live conversation than is possible conversation than is possible through e-mail.through e-mail.

ChatChat Enables user to communicate via Enables user to communicate via

computer in real time, that is computer in real time, that is simultaneously, unlike Instant simultaneously, unlike Instant Messaging chat can occur among Messaging chat can occur among several users.several users.

CookiesCookies: are a tool used by web sites to : are a tool used by web sites to store information about a user. When store information about a user. When visitor enters a web site, site sends a visitor enters a web site, site sends a small text file to the user’s computer so small text file to the user’s computer so that information from the site can be that information from the site can be loaded more quickly on future visitsloaded more quickly on future visits

Streaming MediaStreaming Media

Enables music, video and other large Enables music, video and other large files to be sent to users in chunks so files to be sent to users in chunks so that when received and played, the that when received and played, the files comes through uninterrupted.files comes through uninterrupted.

Streamed files must be viewed live, Streamed files must be viewed live, They can not be stored on client They can not be stored on client hard drive.hard drive.

RealAudio and RealVideo are the RealAudio and RealVideo are the most widely used streaming tools.most widely used streaming tools.