Unit-3

WhatisNetwork?

Anetworkconsistsoftwoormorecomputersthatarelinkedinordertoshareresources(suchasprintersandCDs),exchangefiles,orallowelectroniccommunications.

Twoverycommontypesofnetworksinclude:• LocalAreaNetwork(LAN)• WideAreaNetwork(WAN)

SpecialtypeofNetwork• MetropolitanAreaNetworks(MAN)

LocalAreaNetwork(LAN)ALocalAreaNetwork(LAN)isanetworkthatisconfinedtoarelativelysmallarea.Itisgenerallylimitedtoageographicareasuchasawritinglab,school,orbuilding.

WideAreaNetwork(WAN)

WideAreaNetworks(WANs)connectnetworksinlargergeographicareas,suchasTezpur,India,ortheworld.

MetropolitanAreaNetworks(MAN)Ametropolitanareanetwork(MAN)isanetworkthatinterconnectsuserswithcomputerresourcesinageographicareaorregionlargerthanthatcoveredbyevenalargelocalareanetwork(LAN)butsmallerthantheareacoveredbyawideareanetwork(WAN).

WhatistheInternet?

TheInternetisaglobalnetworkofnetworksconnectingmillionsofusersworldwideviamanycomputernetworksusing IP(Internetprotocol).

WhatdoesInternetProtocolAddress(IPAddress)mean?AnInternetProtocoladdress(IPaddress)isalogicalnumericaddressthatisassignedtoeverysinglecomputer,printer,switch,routeroranyotherdevicethatispartofaTCP/IP-basednetwork.StructureofanIPaddress.192.168.3.10

202.24.23.29

WhatisDomain?

Adomainnameisyourwebsitename.AdomainnameistheaddresswhereInternetuserscanaccessyourwebsite.AdomainnameisusedforfindingandidentifyingcomputersontheInternet.ComputersuseIPaddresses,whichareaseriesofnumber.However,itisdifficultforhumanstorememberstringsofnumbers.Becauseofthis,domainnamesweredevelopedandusedtoidentifyentitiesontheInternetratherthanusingIPaddresses.

Adomainnamecanbeanycombinationoflettersandnumbers,anditcanbeusedincombinationofthevariousdomainnameextensions,suchas.com,.net andmore.

WhatdoesWorldWideWeb(WWW)mean?TheWorldWideWeb(WWW)isanetworkofonlinecontentthatisformattedinHTMLandaccessedviaHTTP.ThetermreferstoalltheinterlinkedHTMLpagesthatcanbeaccessedovertheInternet.TheWorldWideWebwasoriginallydesignedin1991byTimBerners-Lee.

TheWorldWideWebismostoftenreferredtosimplyas"theWeb."

http://www.tezu.ernet.in/

8876401759 nick@1265

HypertextTransferProtocol(HTTP)

HyperText TransferProtocol(HTTP)isanapplication-layerprotocolusedprimarilyontheWorldWideWeb.HTTPusesaclient-servermodelwherethewebbrowseristheclientandcommunicateswiththewebserverthathoststhewebsite.ThebrowserusesHTTP,whichiscarriedoverTCP/IPtocommunicatetotheserverandretrieveWebcontentfortheuser.

WhatdoesUniformResourceLocator(URL)mean?

Auniformresourcelocator(URL)istheaddressofaresourceontheInternet.AURLindicatesthelocationofaresourceaswellastheprotocolusedtoaccessit.

http://www.tezu.ernet.in/

Webbrowser

Awebbrowserisasoftwareprogramthatallowsausertolocate,access,anddisplaywebpages.Browsersareusedprimarilyfordisplayingandaccessingwebsitesontheinternet,aswellasothercontentcreatedusinglanguagessuchasHypertextMarkupLanguage(HTML)andExtensibleMarkupLanguage(XML).BrowserstranslatewebpagesandwebsitesdeliveredusingHypertextTransferProtocol(HTTP)intohuman-readablecontent.Theyalsohavetheabilitytodisplayotherprotocolsandprefixes,suchassecureHTTP(HTTPS)

• E.g:InternetExplorer,MozillaFirefox,GoogleChrome

HTTPS

• Cryptography

• HTTPSstandsforHyperTextTransferProtocolSecure.Itisaprotocolforsecuringthecommunicationbetweentwosystemse.g.thebrowserandthewebserver.

Thefollowingfigureillustratesthedifferencebetweencommunicationoverhttpandhttps:

• Asyoucanseeintheabovefigure,httptransfersdatabetweenthebrowserandthewebserverinthehypertextformat,whereashttpstransfersdataintheencryptedformat.Thus,httpspreventshackersfromreadingandmodifyingthedataduringthetransferbetweenthebrowserandthewebserver.Evenifhackersmanagetointerceptthecommunication,theywillnotbeabletouseitbecausethemessageisencrypted.

• HTTPSestablishedanencryptedlinkbetweenthebrowserandthewebserverusingtheSecureSocketLayer(SSL)orTransportLayerSecurity(TLS)protocols.TLSisthenewversionofSSL.

SSL

• SecureSocketLayer(SSL)• SSListhestandardsecuritytechnologyforestablishinganencryptedlinkbetweenthetwosystems.Thesecanbebrowsertoserver,servertoserverorclienttoserver.Basically,SSLensuresthatthedatatransferbetweenthetwosystemsremainsencryptedandprivate.• ThehttpsisessentiallyhttpoverSSL.SSLestablishesanencryptedlinkusinganSSLcertificatewhichisalsoknownasadigitalcertificate.