WEB TECHNOLOGY First Edition M. Thangavel B.E. (CSE) M.E. (CSE) With the guidance of, R. Sujatha B.Tech (IT), M.E. (CSE) Dedicated to, M.E. Students, Computer Science and Engineering Department, J.J. College of Engineering & Technology, Ammapettai, Poolangulathupatti (Post), Tiruchirappalli - 620 009, Tamil Nadu, India. SYLLABUS UNIT I FUNDAMENTALS Introduction Network Concepts Web Concepts Internet Addresses Retrieving Data with URL HTML DHTML Cascading Style Sheets Scripting Languages Javascript VBscript. UNIT II COMMON GATEWAY INTERFACE Common Gateway Interface Programming CGI Scripts HTML Forms Custom Database Query Scripts Server Side Includes Server Security Issues XML. UNIT III JAVA PROGRAMMING Java Fundamentals Classes Inheritance Packages Interfaces Exceptions Handling Multi threading Applets. UNIT IV SERVER SIDE PROGRAMMING Server Side Programming Active Server Pages Java Server Pages Java Servlets. Servlet Container Exceptions Sessions and Session Tracking Using Servlet Context Dynamic Content Generation Servlet Chaining and Communications. UNIT V APPLICATIONS Simple applications Internet Commerce Database connectivity Online databases EDI Applications in Business Plugins Firewalls. TubIe oI Contents UnIt 1 IundumentuIs l.l InsIc ofwork Concofs------------------------------------------------------- l.l.l ofworks--------------------------------------------------------------------------- l.l.2 Tho !nyors of ofworks-------------------------------------------------------- l.l.3 II,TCI & !I-------------------------------------------------------------------- l.l.4 Tho Infornof----------------------------------------------------------------------- l.l.5 Tho CIIonf/Sorvor ModoI------------------------------------------------------- l.l.6 Infornof Sfnndnrds-------------------------------------------------------------- l.2 InsIc Wob Concofs------------------------------------------------------------- l.2.l !!Is---------------------------------------------------------------------------------- l.2.2 HTM!,SCM! & XM!----------------------------------------------------------- l.2.3 HTTI-------------------------------------------------------------------------------- l.2.4 MIMI ModIn Tyos------------------------------------------------------------- l.2.5 Sorvor SIdo Irogrnms----------------------------------------------------------- l.3 !ockIng u Infornof Addross------------------------------------------------- l.3.l Tho InofAddross CInss--------------------------------------------------------- l.3.2 Inof4Addross nnd Inof6Addross--------------------------------------------- l.3.3 Tho ofwork Inforfnco cInss-------------------------------------------------- l.4 !ofrIovIng nfn wIfh !!!---------------------------------------------------- l.l l.l l.3 l.l0 l.l4 l.l8 l.l9 l.23 l.24 l.29 l.30 l.33 l.34 l.3? l.38 l.45 l.46 l.48 l.5 HTM!-------------------------------------------------------------------------------- A.l InfroducfIon------------------------------------------------------------------------ A.2 IdIfIng HTM!--------------------------------------------------------------------- A.3 IIrsf HTM! IxnmIo----------------------------------------------------------- A.4 Hondors------------------------------------------------------------------------------ A.5 !InkIng------------------------------------------------------------------------------ A.6 Imngos------------------------------------------------------------------------------- A.? SocInI Chnrncfors nnd Moro !Ink Ironks------------------------------- A.8 !nordorod !Isfs------------------------------------------------------------------- A.9 osfod nnd Ordorod !Isfs----------------------------------------------------- A.l0 InsIc HTM! TnbIos-------------------------------------------------------------- A.ll InformodInfo HTM! TnbIos nnd IormnffIng---------------------------- A.l2 InsIc HTM! Iorms-------------------------------------------------------------- A.l3 Moro ComIox HTM! Iorms------------------------------------------------- A.l4 InfornnI !InkIng------------------------------------------------------------------ A.l5 CronfIng nnd !sIng Imngo Mns-------------------------------------------- A.l6 mofn IIomonfs-------------------------------------------------------------------- A.l? frnmosof IIomonf---------------------------------------------------------------- A.l8 osfod Irnmosofs---------------------------------------------------------------- l.6 ynnmIc HTM!------------------------------------------------------------------- l.6.l Objocf ModoI nnd CoIIocfIons------------------------------------------------- I.l InfroducfIon------------------------------------------------------------------------ I.2 Objocf !oforoncIng--------------------------------------------------------------- I.3 CoIIocfIons AII nnd ChIIdron-------------------------------------------------- I.4 ynnmIc SfyIos-------------------------------------------------------------------- I.5 ynnmIc IosIfIonIng------------------------------------------------------------- I.6 !sIng fho Irnmos CoIIocfIon-------------------------------------------------- I.? nnvIgnfor Objocf------------------------------------------------------------------- I.8 Summnry of fho HTM! Objocf ModoI------------------------------------ l.52 l.52 l.52 l.52 l.54 l.55 l.56 l.59 l.60 l.6l l.63 l.66 l.68 l.?0 l.?4 l.?5 l.?? l.?8 l.80 l.8l l.8l l.8l l.82 l.83 l.8? l.90 l.92 l.94 l.96 l.6.2 Ivonf ModoI------------------------------------------------------------------------ C.l InfroducfIon------------------------------------------------------------------------- C.2 Ivonf OnCIIck---------------------------------------------------------------------- C.3 Ivonf On!ond---------------------------------------------------------------------- C.4 Irror HnndIIng wIfh OnIrror------------------------------------------------- C.5 TrnckIng fho Mouso wIfh Ivonf OnMousoMovo------------------------- C.6 !oIIovors wIfh OnMousoOvor & OnMousoOuf--------------------------- C.? Iorm IrocossIng wIfh OnIocus nnd OnIIur----------------------------- C.8 Moro Iorm IrocossIng wIfh OnSubmIf nnd On!osof------------------ C.9 Ivonf IubbIIng-------------------------------------------------------------------- C.l0 Moro HTM! Ivonfs------------------------------------------------------------ l.6.3 IIIfor nnd TrnnsncfIons---------------------------------------------------------- .l III IIIfors: IIIV & IIIH----------------------------------------------------- .2 Trnnsnroncy wIfh Chromn IIIfor-------------------------------------------- .3 CronfIng Imngo Mnsks----------------------------------------------------------- .4 MIscoIInnoous Imngo IIIfors Invorf,Crny,Xrny------------------------ .5 AddIng Shndows fo Toxf--------------------------------------------------------- .6 CronfIng CrndIonfs wIfh A!IHA--------------------------------------------- .? MnkIng Toxf CIow----------------------------------------------------------------- .8 CronfIng MofIon wIfh IIur------------------------------------------------------ .9 !sIng fho wnvo IIIfor------------------------------------------------------------- .l0 Advnncod IIIfors : roShndow nnd !Ighf-------------------------------- .ll TrnnsIfIons I: IIIfor IIondTrnns---------------------------------------------- .l2 TrnnsIfIons II: IIIfor !ovonITrnns------------------------------------------- l.9? l.9? l.98 l.99 l.l0l l.l02 l.l04 l.l09 l.lll l.ll2 l.ll3 l.ll4 l.ll4 l.ll6 l.ll8 l.l20 l.l22 l.l23 l.l26 l.l29 l.l33 l.l34 l.l3? l.l40 l.6.4 nfn IIndIng wIfh TnbuInr nfn ConfroI-------------------------------- I.l InfroducfIon----------------------------------------------------------------------- I.2 SImIo nfn IIndIng----------------------------------------------------------- I.3 MovIng n !ocordSof------------------------------------------------------------- I.4 IIndIng fo nn Img--------------------------------------------------------------- I.5 IIndIng fo n TnbIo--------------------------------------------------------------- I.6 Advnncod SorfIng nnd IIIforIng--------------------------------------------- I.? nfn IIndIng IIomonfs-------------------------------------------------------- l.? CnscndIng SfyIo Shoofs--------------------------------------------------------- I.l InfroducfIon----------------------------------------------------------------------- I.2 InIIno SfyIos----------------------------------------------------------------------- I.3 Imboddod SfyIo Shoofs-------------------------------------------------------- I.4 ConfIIcfIng SfyIos---------------------------------------------------------------- I.5 !InkIng IxfornnI SfyIo Shoofs----------------------------------------------- I.6 IosIfIonIng IIomonfs----------------------------------------------------------- I.? Inckgrounds---------------------------------------------------------------------- I.8 IIomonf ImonsIons----------------------------------------------------------- I.9 Toxf IIow nnd Tho Iox ModoI----------------------------------------------- I.l0 !sor SfyIo Shoofs---------------------------------------------------------------- l.8 JnvnscrIf-------------------------------------------------------------------------- l.8.l InfroducfIon------------------------------------------------------------------------ C.l SImIo Irogrnm: IrInfIng A !Ino Of Toxf In A Wob Ingo---------- C.2 Anofhor JnvnscrIf Irogrnm: AddIng Infogors------------------------- C.3 Momory Concofs---------------------------------------------------------------- C.4 ArIfhmofIc-------------------------------------------------------------------------- C.5 ocIsIon MnkIng: IqunIIfy And !oInfIonnI Oornfors---------------- l.l43 l.l43 l.l43 l.l46 l.l49 l.l50 l.l52 l.l56 l.l5? l.l5? l.l5? l.l58 l.l60 l.l62 l.l64 l.l66 l.l68 l.l69 l.l?3 l.l?4 l.l?4 l.l?4 l.l?8 l.l8l l.l8l l.l83 l.8.2 ConfroI Sfrucfuros-------------------------------------------------------------- H.l InfroducfIon----------------------------------------------------------------------- H.2 AIgorIfhms------------------------------------------------------------------------- H.3 Isoudocodo------------------------------------------------------------------------ H.4 ConfroI Sfrucfuros-------------------------------------------------------------- H.5 II SoIocfIon Sfrucfuro--------------------------------------------------------- H.6 II/I!SI SoIocfIon Sfrucfuro------------------------------------------------ H.? WhIIo !oofIfIon Sfrucfuro-------------------------------------------------- H.8 Counfor ConfroIIod !oofIfIon---------------------------------------------- H.9 SonfInoI ConfroIIod !oofIfIon---------------------------------------------- H.l0 AssIgnmonf Oornfors--------------------------------------------------------- H.ll Incromonf nnd ocromonf Oornfors------------------------------------- H.l2 ofo on nfn Tyos------------------------------------------------------------- H.l3 IssonfInIs of Counfor-ConfroIIod !oofIfIon--------------------------- H.l4 Ior !oofIfIon Sfrucfuro------------------------------------------------------ H.l5 SwIfch MuIfIIo SoIocfIon Sfrucfuro-------------------------------------- H.l6 O/WHI!I !oofIfIon Sfrucfuro------------------------------------------ H.l? Ironk nnd ConfInuo Sfnfomonfs------------------------------------------- H.l8 !nboIod Ironk nnd ConfInuo Sfnfomonfs------------------------------- H.l9 !ogIcnI Oornfors--------------------------------------------------------------- l.8.3 IuncfIons-------------------------------------------------------------------------- I.l InfroducfIon----------------------------------------------------------------------- I.2 Irogrnm ModuIos In JnvnScrIf-------------------------------------------- I.3 Irogrnmmor ofInod IuncfIons--------------------------------------------- I.4 IuncfIon ofInIfIons------------------------------------------------------------ I.5 !nndom umbor ConornfIon------------------------------------------------ I.6 urnfIon of IdonfIfIors--------------------------------------------------------- l.l86 l.l86 l.l86 l.l86 l.l8? l.l88 l.l89 l.l92 l.l92 l.l94 l.l96 l.l9? l.l98 l.l99 l.200 l.204 l.206 l.20? l.208 l.2l0 l.2l2 l.2l2 l.2l2 l.2l2 l.2l3 l.2l6 l.2l? I.? Scoo !uIos------------------------------------------------------------------------ I.8 JnvnscrIf CIobnI IuncfIons------------------------------------------------- I.9 !ocursIon--------------------------------------------------------------------------- I.l0 IxnmIo usIng !ocursIon : IIbonnccI SorIos---------------------------- I.ll !ocursIon vs IfornfIon---------------------------------------------------------- l.8.5 Arrnys------------------------------------------------------------------------------- J.l InfroducfIon----------------------------------------------------------------------- J.2 Arrnys------------------------------------------------------------------------------- J.3 ocInrIng nnd AIIocnfIng Arrnys------------------------------------------- J.4 !oforoncos nnd !oforonco Inrnmofors----------------------------------- J.5 InssIng Arrnys fo IuncfIons------------------------------------------------- J.6 SorfIng Arrnys------------------------------------------------------------------- J.? SonrchIng Arrnys : !Inonr Sonrch & IInnry Sonrch------------------ J.8 MuIfIIo SubscrIfod Arrnys------------------------------------------------- l.8.5 Objocfs------------------------------------------------------------------------------- K.l InfroducfIon------------------------------------------------------------------------ K.2 Mnfh Objocf------------------------------------------------------------------------ K.3 SfrIng Objocf----------------------------------------------------------------------- K.3.l IundnmonfnIs Of Chnrncfors And SfrIngs------------------------------- K.3.2 Mofhods Of Tho SfrIng Objocf----------------------------------------------- K.3.3 Chnrncfor IrocossIng Mofhods----------------------------------------------- K.3.4 SonrchIng Mofhods-------------------------------------------------------------- K.3.5 SIIffIng SfrIngs nnd ObfnInIng SubsfrIngs----------------------------- K.3.6 HTM! Mnrku Mofhods------------------------------------------------------- l.2l? l.2l9 l.220 l.22l l.223 l.224 l.224 l.224 l.225 l.22? l.22? l.229 l.230 l.234 l.236 l.236 l.236 l.23? l.23? l.238 l.240 l.240 l.24l l.243 K.4 ATI Objocf----------------------------------------------------------------------- K.5 IooIonn And umbor Objocfs------------------------------------------------- l.9 VIScrIf------------------------------------------------------------------------------ !.l InfroducfIon------------------------------------------------------------------------- !.2 Oornfors---------------------------------------------------------------------------- !.3 nfn Tyos nnd ConfroI Sfrucfuros----------------------------------------- !.4 VIScrIf IuncfIons--------------------------------------------------------------- !.5 VIScrIf IxnmIo Irogrnms-------------------------------------------------- !.6 Arrnys--------------------------------------------------------------------------------- !.? SfrIng MnnIuInfIon-------------------------------------------------------------- !.8 CInssos & Objocfs----------------------------------------------------------------- !.9 Oornfor Irocodonco------------------------------------------------------------- UnIt 2 Common Gutewuy IntevIuce 2.l Common Cnfowny Inforfnco (CCI)------------------------------------------ A.l SomofhIngs fo !omombor nbouf CCI------------------------------------- A.2 !so of CCI ScrIfs--------------------------------------------------------------- A.3 Why uso CCI` -------------------------------------------------------------------- A.4 Why nof !so CCI` -------------------------------------------------------------- 2.2 IrogrnmmIng CCI ScrIfs---------------------------------------------------- I.l CCI & WorId WIdo Wob------------------------------------------------------- I.2 Ioyond XHTM! WIfh CCI---------------------------------------------------- I.3 How CCI Works` ---------------------------------------------------------------- I.4 Whoro CCI ScrIfs !Ivo` ----------------------------------------------------- l.244 l.246 l.24? l.24? l.24? l.248 l.25l l.253 l.25? l.259 l.262 l.265 2.l 2.l 2.2 2.2 2.3 2.3 2.3 2.4 2.5 2.9 I.5 CCI Sorvor !oquIromonfs---------------------------------------------------- I.6 CCI ScrIf Sfrucfuro----------------------------------------------------------- I.? IInnnIng Your ScrIf----------------------------------------------------------- I.8 Sfnndnrd CCI InvIronmonf VnrInbIos----------------------------------- I.9 CCI ScrIf IorfnbIIIfy---------------------------------------------------------- I.l0 Tho Iufuro of CCI ScrIfIng------------------------------------------------- 2.3 HTM! Iorms--------------------------------------------------------------------- C.l Iorms nnd CCI------------------------------------------------------------------- C.2 CronfIng Iorms------------------------------------------------------------------ C.3 !nboIIng Inuf IIoIds---------------------------------------------------------- C.4 CrouIng !oInfod IIoIds------------------------------------------------------ C.5 IsnbIod nnd !ond OnIy IIoIds--------------------------------------------- C.6 Iorm IIoId Ivonf HnndIors-------------------------------------------------- C.? InssIng Irom nfn------------------------------------------------------------- 2.4 Cusfom nfnbnso Quory ScrIfs-------------------------------------------- .l !ndorsfnndIng nfnbnso osIgn-------------------------------------------- .2 Why Accoss nfnbnso` --------------------------------------------------------- .3 nfnbnso Accoss !ImIfnfIons------------------------------------------------- .4 CronfIng nnd !sIng IInf IIIo nfnbnsos---------------------------------- .5 IM nfnbnsos------------------------------------------------------------------ .6 !oInfIonnI nfnbnsos----------------------------------------------------------- .? obuggIng nfnbnso AIIcnfIons------------------------------------------ 2.5 Sorvor SIdo IncIudos------------------------------------------------------------- I.l SSI SocIfIcnfIon------------------------------------------------------------------ I.2 ConfIgurIng SSI-------------------------------------------------------------------- I.3 !sIng SSI In XHTM!------------------------------------------------------------ I.4 Common SSI Commnnds------------------------------------------------------- 2.9 2.ll 2.l4 2.l5 2.l6 2.l9 2.2l 2.2l 2.22 2.36 2.3? 2.39 2.40 2.4l 2.42 2.42 2.43 2.43 2.44 2.46 2.49 2.52 2.53 2.53 2.54 2.55 2.56 2.6 Sorvor SIdo SocurIfy Issuos----------------------------------------------------- I.l ScrIf vorsus Irogrnms---------------------------------------------------------- I.2 CCI SocurIfy Issuos: !ocognIzIng IrobIoms & IIndIng SoIufIons- I.3 InsIdo Affncks: IrocnufIons WIfh !ocnI !sors--------------------------- 2.? XM!------------------------------------------------------------------------------------ I.l Whnf Is XM!` ---------------------------------------------------------------------- I.2 Ifforonco bofwoon XM! & HTM!------------------------------------------- I.3 How cnn XM! Ioon !sod` ----------------------------------------------------- I.4 XM! Troo----------------------------------------------------------------------------- I.5 XM! Synfnx !uIos----------------------------------------------------------------- I.6 XM! IIomonfs---------------------------------------------------------------------- I.? XM! AffrIbufos--------------------------------------------------------------------- UnIt 3 Juvu PvogvummIng 3.l Tho ConosIs of Jnvn------------------------------------------------------------- A.l Tho CronfIon of Jnvn----------------------------------------------------------- A.2 Why Jnvn Is Imorfnnf fo fho Infornof----------------------------------- A.3 Jnvn`s MngIc: Tho Iyfocodo-------------------------------------------------- A.4 Tho Jnvn Iuzzwords------------------------------------------------------------ 3.2 An OvorvIow of Jnvn------------------------------------------------------------ I.l Objocf-OrIonfod IrogrnmmIng---------------------------------------------- I.2 A IIrsf SImIo Irogrnm------------------------------------------------------- I.3 A Socond Shorf Irogrnm------------------------------------------------------ I.4 Two ConfroI Sfnfomonfs------------------------------------------------------- I.5 !sIng IIocks of Codo----------------------------------------------------------- I.6 !oxIcnI Issuos--------------------------------------------------------------------- I.? Tho Jnvn CInss !IbrnrIos------------------------------------------------------ 2.59 2.59 2.60 2.?3 2.?6 2.?6 2.?6 2.?? 2.?9 2.82 2.86 2.88 3.l 3.l 3.l 3.3 3.4 3.6 3.6 3.l0 3.l3 3.l4 3.l? 3.l9 3.2l 3.3 nfn Tyos, VnrInbIos, nnd Arrnys----------------------------------------- C.l Jnvn Is n SfrongIy Tyod !nngungo---------------------------------------- C.2 Tho SImIo Tyos---------------------------------------------------------------- C.3 Infogors----------------------------------------------------------------------------- C.4 IIonfIng-IoInf Tyos----------------------------------------------------------- C.5 Chnrncfors-------------------------------------------------------------------------- C.6 IooIonns----------------------------------------------------------------------------- C.? VnrInbIos--------------------------------------------------------------------------- C.8 Tyo ConvorsIon nnd CnsfIng----------------------------------------------- C.9 Arrnys------------------------------------------------------------------------------- 3.4 Oornfors--------------------------------------------------------------------------- .l ArIfhmofIc Oornfors----------------------------------------------------------- .2 Tho IIfwIso Oornfors---------------------------------------------------------- .3 !oInfIonnI Oornfors------------------------------------------------------------ .4 IooIonn !ogIcnI Oornfors---------------------------------------------------- .5 Tho AssIgnmonf Oornfor----------------------------------------------------- .6 Tho ` Oornfor-------------------------------------------------------------------- .? Oornfor Irocodonco------------------------------------------------------------ 3.5 ConfroI Sfnfomonfs-------------------------------------------------------------- I.l Jnvn`s SoIocfIon Sfnfomonfs--------------------------------------------------I.2 IfornfIon Sfnfomonfs------------------------------------------------------------ I.3 Jum Sfnfomonfs----------------------------------------------------------------- 3.6 InfroducIng CInssos------------------------------------------------------------- I.l CInss IundnmonfnIs------------------------------------------------------------- I.2 ocInrIng Objocfs----------------------------------------------------------------- 3.2l 3.2l 3.22 3.22 3.23 3.24 3.25 3.26 3.29 3.30 3.34 3.34 3.39 3.42 3.43 3.44 3.44 3.45 3.46 3.46 3.49 3.53 3.55 3.55 3.5? I.3 AssIgnIng Objocf !oforonco VnrInbIos-------------------------------------I.4 InfroducIng Mofhods------------------------------------------------------------ I.5 Consfrucfors----------------------------------------------------------------------- I.6 Tho fhIs Koyword----------------------------------------------------------------- I.? Cnrbngo CoIIocfIon--------------------------------------------------------------- I.8 Tho fInnIIzo( ) Mofhod----------------------------------------------------------- I.9 A Sfnck CInss---------------------------------------------------------------------- I.l0 OvorIondIng Mofhods------------------------------------------------------------ I.ll !sIng Objocfs ns Inrnmofors------------------------------------------------- I.l2 Argumonf InssIng---------------------------------------------------------------- I.l3 !ofurnIng Objocfs---------------------------------------------------------------- I.l4 !ocursIon---------------------------------------------------------------------------- I.l5 Accoss ConfroI--------------------------------------------------------------------- I.l6 sfnfIc--------------------------------------------------------------------------------- I.l? IInnI--------------------------------------------------------------------------------- I.l8 osfod nnd Innor CInssos----------------------------------------------------- I.l9 Tho SfrIng CInss----------------------------------------------------------------- I.20 Commnnd-!Ino Argumonfs--------------------------------------------------- 3.? InhorIfnnco------------------------------------------------------------------------- C.l InhorIfnnco InsIcs--------------------------------------------------------------- C.2 !sIng Suor------------------------------------------------------------------------ C.3 MuIfIIovoI HIornrchy------------------------------------------------------------ C.4 Whon Consfrucfors Aro CnIIod----------------------------------------------- C.5 Mofhod OvorrIdIng--------------------------------------------------------------- C.6 ynnmIc Mofhod Isnfch---------------------------------------------------- C.? !sIng Absfrncf CInssos--------------------------------------------------------- C.8 !sIng fInnI wIfh InhorIfnnco-------------------------------------------------- C.9 Tho Objocf CInss------------------------------------------------------------------ 3.5? 3.58 3.62 3.64 3.65 3.66 3.66 3.69 3.?l 3.?2 3.?4 3.?5 3.?6 3.?? 3.?9 3.?9 3.8l 3.83 3.84 3.84 3.88 3.92 3.95 3.96 3.9? 3.l0l 3.l03 3.l04 3.8 Inckngos nnd Inforfncos------------------------------------------------------- H.l Inckngos--------------------------------------------------------------------------- H.2 Accoss IrofocfIon---------------------------------------------------------------- H.3 ImorfIng Inckngos------------------------------------------------------------ H.4 Inforfncos-------------------------------------------------------------------------- 3.9 IxcofIon HnndIIng------------------------------------------------------------- I.l IxcofIon-HnndIIng IundnmonfnIs---------------------------------------- I.2 IxcofIon Tyos------------------------------------------------------------------- I.3 !ncnughf IxcofIons------------------------------------------------------------ I.4 !sIng fry nnd cnfch-------------------------------------------------------------- I.5 MuIfIIo cnfch CInusos---------------------------------------------------------- I.6 osfod fry Sfnfomonfs----------------------------------------------------------- I.? fhrow---------------------------------------------------------------------------------- I.8 fhrows--------------------------------------------------------------------------------- I.9 fInnIIy--------------------------------------------------------------------------------- I.l0 Jnvn`s IuIIf-In IxcofIons------------------------------------------------------ I.ll CronfIng Your Own IxcofIon SubcInssos--------------------------------- I.l2 ChnInod IxcofIons--------------------------------------------------------------- 3.l0 MuIfIfhrondod IrogrnmmIng-------------------------------------------------- J.l Tho Jnvn Thrond ModoI--------------------------------------------------------- J.2 Tho MnIn Thrond----------------------------------------------------------------- J.3 CronfIng n Thrond---------------------------------------------------------------- J.4 CronfIng MuIfIIo Thronds----------------------------------------------------- J.5 !sIng IsAIIvo( ) nnd joIn( )----------------------------------------------------- J.6 Thrond IrIorIfIos------------------------------------------------------------------ J.? SynchronIznfIon------------------------------------------------------------------ J.8 Inforfhrond CommunIcnfIon-------------------------------------------------- J.9 SusondIng, !osumIng, nnd SfoIng Thronds------------------------- J.l0 !sIng MuIfIfhrondIng----------------------------------------------------------- 3.l05 3.l06 3.l08 3.lll 3.ll2 3.l20 3.l20 3.l2l 3.l2l 3.l22 3.l24 3.l26 3.l2? 3.l28 3.l29 3.l30 3.l3l 3.l33 3.l35 3.l35 3.l38 3.l40 3.l44 3.l45 3.l48 3.l50 3.l54 3.l59 3.l6l 3.ll I/O InsIcs-------------------------------------------------------------------------- K.l Sfronms----------------------------------------------------------------------------- K.2 !ondIng ConsoIo Inuf--------------------------------------------------------- K.3 WrIfIng ConsoIo Oufuf------------------------------------------------------- K.4 Tho IrInfWrIfor CInss--------------------------------------------------------- K.5 !ondIng nnd WrIfIng IIIos---------------------------------------------------- 3.l2 Tho AIof-------------------------------------------------------------------------- !.l AIof InsIcs---------------------------------------------------------------------- !.2 AIof ArchIfocfuro------------------------------------------------------------- !.3 An AIof SkoIofon-------------------------------------------------------------- !.4 SImIo AIof IsIny Mofhods--------------------------------------------- !.5 !oquosfIng !onInfIng--------------------------------------------------------- !.6 Tho HTM! AII!IT Tng------------------------------------------------------!.? Tho AudIoCII Inforfnco------------------------------------------------------- !.8 Tho AIofSfub Inforfnco----------------------------------------------------- !.9 OufuffIng fo fho ConsoIo---------------------------------------------------- !.l0 AIof Irogrnms----------------------------------------------------------------- 3.l6l 3.l6l 3.l64 3.l66 3.l66 3.l6? 3.l?l 3.l?l 3.l?4 3.l?4 3.l?? 3.l?9 3.l80 3.l82 3.l82 3.l83 3.l83 UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l

UNIT I IUNAMNTAIS 1.1 BASIC NTWORK CONCPTS 1.1.1 NTWORKS A nofwork Is n coIIocfIon of comufors nnd ofhor dovIcos fhnf cnn sond dnfn fo nnd rocoIvo dnfn from onch ofhor, moro or Ioss In ronI fImo. A nofwork Is offon connocfod by wIros, nnd fho bIfs of dnfn nro furnod Info oIocfromngnofIc wnvos fhnf movo fhrough fho wIros. Howovor, wIroIoss nofworks frnnsmIf dnfn fhrough Infrnrod IIghf nnd mIcrownvos, nnd mnny Iong-dIsfnnco frnnsmIssIons nro now cnrrIod ovor fIbor ofIc cnbIos fhnf sond vIsIbIo IIghf fhrough gInss fIInmonfs. Node Inch mnchIno on n nofwork Is cnIIod n nodo. Mosf nodos nro comufors, buf rInfors, roufors, brIdgos, gnfownys, dumb formInnIs, nnd Cocn-CoIn mnchInos cnn nIso bo nodos. odos fhnf nro fuIIy funcfIonnI comufors nro nIso cnIIod hosfs. Wo wIII uso fho word nodo fo rofor fo nny dovIco on fho nofwork, nnd fho word hosf fo rofor fo n nodo fhnf Is n gonornI-uroso comufor. Addvess Ivory nofwork nodo hns nn nddross, n sorIos of byfos fhnf unIquoIy IdonfIfy If. In gonornI fho numbor of byfos In nn nddross or fho ordorIng of fhoso byfos (bIg ondInn or IIffIo ondInn) Is nof gunrnnfood fo mnfch nny rImIfIvo numorIc dnfn fyo In Jnvn. Tho moro byfos fhoro nro In onch nddross, fho moro nddrossos fhoro nro nvnIInbIo nnd fho moro dovIcos fhnf cnn bo connocfod fo fho nofwork sImuIfnnoousIy. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.2

Addrossos nro nssIgnod dIfforonfIy on dIfforonf kInds of nofworks. AIoTnIk nddrossos nro choson rnndomIy nf sfnrfu by onch hosf. Tho hosf fhon chocks fo soo If nny ofhor mnchIno on fho nofwork Is usIng fhnf nddross. If nnofhor mnchIno Is usIng fho nddross, fho hosf rnndomIy choosos nnofhor, chocks fo soo If fhnf nddross Is nIrondy In uso, nnd so on unfII If gofs ono fhnf Isn'f boIng usod. Ifhornof nddrossos nro nffnchod fo fho hysIcnI Ifhornof hnrdwnro. Inch mnnufncfuror Is rosonsIbIo for mnkIng suro If doosn'f shI fwo Ifhornof cnrds wIfh fho snmo nddross. Intevnet SevvIce PvovIdev (ISP) Tho nddrossos fhnf nn orgnnIznfIon Is nIIowod fo chooso for Ifs comufors nro nssIgnod by fho orgnnIznfIon's Infornof SorvIco IrovIdor (ISI). ISIs gof fhoIr II nddrossos from ono of four rogIonnI Infornof !ogIsfrIos, whIch nro In furn nssIgnod II nddrossos by fho Infornof CorornfIon for AssIgnod nmos nnd umbors (ICA, nf hff://www.Icnnn.org/). Pucket-SwItcLed netwovks AII modorn comufor nofworks nro nckof-swIfchod nofworks: dnfn frnvoIIng on fho nofwork Is brokon Info chunks cnIIod nckofs nnd onch nckof Is hnndIod sonrnfoIy. Inch nckof confnIns InformnfIon nbouf who sonf If nnd whoro If's goIng. Tho mosf Imorfnnf ndvnnfngo of bronkIng dnfn Info IndIvIdunIIy nddrossod nckofs Is fhnf nckofs from mnny ongoIng oxchnngos cnn frnvoI on ono wIro, whIch mnkos If much chonor fo buIId n nofwork: mnny comufors cnn shnro fho snmo wIro wIfhouf InforforIng. Anofhor ndvnnfngo of nckofs Is fhnf chocksums cnn bo usod fo dofocf whofhor n nckof wns dnmngod In frnnsIf. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.3

PvotocoI A rofocoI Is n rocIso sof of ruIos dofInIng how comufors communIcnfo: fho formnf of nddrossos, how dnfn Is sIIf Info nckofs, nnd so on. Thoro nro mnny dIfforonf rofocoIs dofInIng dIfforonf nsocfs of nofwork communIcnfIon. Ior oxnmIo, fho Hyorfoxf Trnnsfor IrofocoI (HTTI) dofInos how wob browsors nnd sorvors communIcnfo; nf fho ofhor ond of fho socfrum, fho IIII 802.3 sfnndnrd dofInos n rofocoI for how bIfs nro oncodod ns oIocfrIcnI sIgnnIs on n nrfIcuInr fyo of wIro (nmong ofhor rofocoIs). 1.1.2 TH IAYRS OI A NTWORK WLy It Is needed? SondIng dnfn ncross n nofwork Is n comIox oornfIon fhnf musf bo cnrofuIIy funod fo fho hysIcnI chnrncforIsfIcs of fho nofwork ns woII ns fho IogIcnI chnrncfor of fho dnfn boIng sonf. Soffwnro fhnf sonds dnfn ncross n nofwork musf undorsfnnd how fo nvoId coIIIsIons bofwoon nckofs, convorf dIgIfnI dnfn fo nnnIog sIgnnIs, dofocf nnd corrocf orrors, roufo nckofs from ono hosf fo nnofhor, nnd moro. Tho rocoss bocomos ovon moro comIIcnfod whon fho roquIromonf fo suorf muIfIIo oornfIng sysfoms nnd hoforogonoous nofwork cnbIIng Is nddod. To mnko fhIs comIoxIfy mnnngonbIo nnd hIdo mosf of If from fho nIIcnfIon dovoIoor nnd ond usor, fho dIfforonf nsocfs of nofwork communIcnfIon nro sonrnfod Info muIfIIo Inyors. Inch Inyor rorosonfs n dIfforonf IovoI of nbsfrncfIon bofwoon fho hysIcnI hnrdwnro (o.g., fho wIros nnd oIocfrIcIfy) nnd fho InformnfIon boIng frnnsmIffod. Inch Inyor hns n sfrIcfIy IImIfod funcfIon. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.4

Thoro nro sovornI dIfforonf Inyor modoIs, onch orgnnIzod fo fIf fho noods of n nrfIcuInr kInd of nofwork. Tho sfnndnrd TCI/II four-Inyor modoI nrorInfo for fho Infornof, In fhIs modoI, nIIcnfIons IIko Infornof IxIoror nnd Iudorn run In fho upplicution luyer nnd fnIk onIy fo fho frnnsorf Inyor. Tho trunoport luyer fnIks onIy fo fho nIIcnfIon Inyor nnd fho Infornof Inyor. Tho internet luyer In furn fnIks onIy fo fho hosf-fo-nofwork Inyor nnd fho frnnsorf Inyor, novor dIrocfIy fo fho nIIcnfIon Inyor. Tho hoot-to-netuork luyer movos fho dnfn ncross fho wIros, fIbor ofIc cnbIos, or ofhor modIum fo fho hosf-fo-nofwork Inyor on fho romofo sysfom, whIch fhon movos fho dnfn u fho Inyors fo fho nIIcnfIon on fho romofo sysfom. The luyero of u netuork Sendev SIde Whon n wob browsor sonds n roquosf fo n wob sorvor fo rofrIovo n ngo, fho browsor Is ncfunIIy onIy fnIkIng fo fho frnnsorf Inyor on fho IocnI cIIonf mnchIno. Tho trunoport luyer bronks fho roquosf u Info TCI sogmonfs, ndds somo soquonco numbors nnd chocksums fo fho dnfn, nnd fhon nssos fho roquosf fo fho IocnI Infornof Inyor. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.5

Tho internet luyer frngmonfs fho sogmonfs Info II dnfngrnms of fho nocossnry sIzo for fho IocnI nofwork nnd nssos fhom fo fho hosf-fo-nofwork Inyor for frnnsmIssIon onfo fho wIro. Tho hoot-to-netuork luyer oncodos fho dIgIfnI dnfn ns nnnIog sIgnnIs nrorInfo for fho nrfIcuInr hysIcnI modIum nnd sonds fho roquosf ouf fho wIro whoro If wIII bo rond by fho hosf-fo-nofwork Inyor of fho romofo sysfom fo whIch If's nddrossod. ReceIvev SIde Tho hoot-to-netuork luyer on fho romofo sysfom docodos fho nnnIog sIgnnIs Info dIgIfnI dnfn fhon nssos fho rosuIfIng II dnfngrnms fo fho sorvor's Infornof Inyor. Tho internet luyer doos somo sImIo chocks fo soo fhnf fho II dnfngrnms nron'f corruf, ronssombIos fhom If fhoy'vo boon frngmonfod, nnd nssos fhom fo fho sorvor's frnnsorf Inyor. Tho sorvor's trunoport luyer chocks fo soo fhnf nII fho dnfn nrrIvod nnd roquosfs rofrnnsmIssIon of nny mIssIng or corruf Iocos. Onco fho sorvor's frnnsorf Inyor hns rocoIvod onough confIguous, soquonfInI dnfngrnms, If ronssombIos fhom nnd wrIfos fhom onfo n sfronm rond by fho wob sorvor runnIng In fho sorvor upplicution luyer. Tho oerter rosonds fo fho roquosf nnd sonds Ifs rosonso bnck down fhrough fho Inyors on fho sorvor sysfom for frnnsmIssIon bnck ncross fho Infornof nnd doIIvory fo fho wob cIIonf. TLe Host-to-Netwovk Iuyev In fho sfnndnrd roforonco modoI for II-bnsod Infornofs, fho hIddon nrfs of fho nofwork boIong fo fho hosf-fo-nofwork Inyor. Tho Hosf-fo-nofwork Inyors nIso known ns the link luyer, Jutu link luyer, or netuork interfuce luyer. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.6

Tho hosf-fo-nofwork Inyor dofInos how n nrfIcuInr nofwork Inforfncosuch ns nn Ifhornof cnrd or n III connocfIonsonds II dnfngrnms ovor Ifs hysIcnI connocfIon fo fho IocnI nofwork nnd fho worId. Tho nrf of fho hosf-fo-nofwork Inyor mndo u of fho hnrdwnro fhnf connocfs dIfforonf comufors (wIros, fIbor ofIc cnbIos, mIcrownvo roInys, or smoko sIgnnIs) Is somofImos cnIIod fho phyoicul luyer of fho nofwork. Computevs to communIcute wItL eucL otLev Ior computero to communicute uith euch other, If Isn'f suffIcIonf fo run wIros bofwoon fhom nnd sond oIocfrIcnI sIgnnIs bnck nnd forfh. Tho comufors hnvo fo ngroo on corfnIn sfnndnrds for how fhoso sIgnnIs nro Inforrofod. Tho fIrsf sfo Is fo doformIno how fho nckofs of oIocfrIcIfy or IIghf or smoko mn Info bIfs nnd byfos of dnfn. SInco fho hysIcnI Inyor Is nnnIog, nnd bIfs nnd byfos nro dIgIfnI, fhIs rocoss InvoIvos n dIgIfnI-fo-nnnIog convorsIon on fho sondIng ond nnd nn nnnIog-fo-dIgIfnI convorsIon on fho rocoIvIng ond. SInco nII ronI nnnIog sysfoms hnvo noIso, orror corrocfIon nnd rodundnncy nood fo bo buIIf Info fho wny dnfn Is frnnsInfod Info oIocfrIcIfy. ThIs Is dono In fho dnfn IInk Inyor. Tho mosf common dnfn IInk Inyor Is Ifhornof. Ofhor ouInr dnfn IInk Inyors IncIudo Tokon!Ing, III, nnd WIroIoss Ifhornof (802.ll). A socIfIc dnfn IInk Inyor roquIros socInIIzod hnrdwnro. SocInI dovIcos cnIIod guteuuyo convorf InformnfIon from ono fyo of dnfn IInk Inyor, such ns Ifhornof, fo nnofhor, such ns Tokon!Ing. TLe Intevnet Iuyev Tho noxf Inyor of fho nofwork, nnd fho fIrsf fhnf you nood fo concorn yoursoIf wIfh, Is fho Infornof Inyor. In fho OSI modoI, fho Infornof Inyor goos by fho moro gonorIc nnmo nofwork Inyor. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.?

A nofwork Inyor rofocoI dofInos how bIfs nnd byfos of dnfn nro orgnnIzod Info fho Inrgor grous cnIIod nckofs, nnd fho nddrossIng schomo by whIch dIfforonf mnchInos fInd onch ofhor. Tho Infornof IrofocoI (II) Is fho mosf wIdoIy usod nofwork Inyor rofocoI In fho worId nnd fho onIy nofwork Inyor rofocoI. Inch nofwork Inyor rofocoI Is Indoondonf of fho Iowor Inyors. II, IIX, ofII!I, nnd ofhor rofocoIs cnn onch bo usod on Ifhornof, Tokon !Ing, nnd ofhor dnfn IInk Inyor rofocoI nofworks, onch of whIch cnn fhomsoIvos run ncross dIfforonf kInds of hysIcnI Inyors. nfn Is sonf ncross fho Infornof Inyor In nckofs cnIIod dnfngrnms. Inch II dnfngrnm confnIns n hondor bofwoon 20 nnd 60 byfos Iong nnd n nyIond fhnf confnIns u fo 65,5l5 byfos of dnfn. Tho hondor of onch II dnfngrnm confnIns fhoso Ifoms, In fhIs ordor: 4-bit teroion number AIwnys 0l00 (docImnI 4) for curronf II; wIII bo chnngod fo 0ll0 (docImnI 6) for IIv6, buf fho onfIro hondor formnf wIII nIso chnngo In IIv6. 4-bit heuJer length An unsIgnod Infogor bofwoon 0 nnd l5 socIfyIng fho numbor of 4-byfo words In fho hondor; sInco fho mnxImum vnIuo of fho hondor Iongfh fIoId Is llll (docImnI l5), nn II hondor cnn bo nf mosf 60 byfos Iong. 1-byte type of oertice A 3-bIf rocodonco fIoId fhnf Is no Iongor usod, four fyo-of-sorvIco bIfs (mInImIzo doIny, mnxImIzo fhroughuf, mnxImIzo roIInbIIIfy, mInImIzo monofnry cosf) nnd n zoro bIf. of nII sorvIco fyos nro comnfIbIo. Mnny comufors nnd roufors sImIy Ignoro fhoso bIfs. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.8

2-byte Jutugrum length An unsIgnod Infogor socIfyIng fho Iongfh of fho onfIro dnfngrnm, IncIudIng bofh hondor nnd nyIond. 2-byte iJentificution number A unIquo IdonfIfIor for onch dnfngrnm sonf by n hosf; nIIows duIIcnfo dnfngrnms fo bo dofocfod nnd fhrown nwny. 3-bit flugo Tho fIrsf bIf Is 0; fho socond bIf Is 0 If fhIs dnfngrnm mny bo frngmonfod, l If If mny nof bo; nnd fho fhIrd bIf Is 0 If fhIs Is fho Insf frngmonf of fho dnfngrnm, l If fhoro nro moro frngmonfs. 13-bit frugment offoet In fho ovonf fhnf fho orIgInnI II dnfngrnm Is frngmonfod Info muIfIIo Iocos, fhIs fIoId IdonfIfIos fho osIfIon of fhIs frngmonf In fho orIgInnI dnfngrnm. 1-byte time-to-lite (TTL) umbor of nodos fhrough whIch fho dnfngrnm cnn nss boforo boIng dIscnrdod; usod fo nvoId InfInIfo Ioos. 1-byte protocol 6 for TCI, l? for !I, or n dIfforonf numbor bofwoon 0 nnd 255 for onch of moro fhnn l00 dIfforonf rofocoIs (somo quIfo obscuro); 2-byte heuJer checkoum A chocksum of fho hondor onIy (nof fho onfIro dnfngrnm) cnIcuInfod usIng n l6-bIf ono's comIomonf sum. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.9

4-byte oource uJJreoo Tho II nddross of fho sondIng nodo. 4-byte Jeotinution uJJreoo Tho II nddross of fho dosfInnfIon nodo. An II dnfngrnm hondor mny confnIn bofwoon 0 nnd 40 byfos of ofIonnI InformnfIon, usod for socurIfy ofIons, roufIng rocords, fImosfnms, nnd ofhor fonfuros Jnvn doos nof suorf. The otructure of un 1Pt4 Jutugrum TLe Tvunspovt Iuyev Tho frnnsorf Inyor Is rosonsIbIo for onsurIng fhnf nckofs nro rocoIvod In fho ordor fhoy woro sonf nnd mnkIng suro fhnf no dnfn Is Iosf or corrufod. If n nckof Is Iosf, fho frnnsorf Inyor cnn nsk fho sondor fo rofrnnsmIf fho nckof. II nofworks ImIomonf fhIs by nddIng nn nddIfIonnI hondor fo onch dnfngrnm fhnf confnIns moro InformnfIon. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l0

Thoro nro fwo rImnry rofocoIs nf fhIs IovoI. Tho fIrsf, fho TrnnsmIssIon ConfroI IrofocoI (TCI), Is n hIgh-ovorhond rofocoI fhnf nIIows for rofrnnsmIssIon of Iosf or corrufod dnfn nnd doIIvory of byfos In fho ordor fhoy woro sonf. Tho socond rofocoI, fho !sor nfngrnm IrofocoI (!I), nIIows fho rocoIvor fo dofocf corrufod nckofs buf doos nof gunrnnfoo fhnf nckofs nro doIIvorod In fho corrocf ordor (or nf nII). Howovor, !I Is offon much fnsfor fhnn TCI. TCI Is cnIIod n reliuble protocol; !I Is nn unreliuble protocol. TLe AppIIcutIon Iuyev Tho Inyor fhnf doIIvors dnfn fo fho usor Is cnIIod fho nIIcnfIon Inyor. Tho fhroo Iowor Inyors nII work fogofhor fo dofIno how dnfn Is frnnsforrod from ono comufor fo nnofhor. Tho nIIcnfIon Inyor docIdos whnf fo do wIfh fho dnfn nffor If's frnnsforrod. Tho nIIcnfIon Inyor Is whoro mosf of fho nofwork nrfs of your rogrnms sond fhoIr fImo. Thoro Is nn onfIro nIhnbof sou of nIIcnfIon Inyor rofocoIs; In nddIfIon fo HTTI for fho Wob, fhoro nro SMTI, IOI, nnd IMAI for omnII; ITI, ISI, nnd TITI for fIIo frnnsfor; IS for fIIo nccoss; TI for nows frnnsfor; CnufoIIn, InsfTrnck, nnd Iroo nof for fIIo shnrIng; nnd mnny, mnny moro. 1.1.3 IP, TCP, und UP 1P, fho Infornof rofocoI, hns n numbor of ndvnnfngos ovor comofIng rofocoIs such ns AIoTnIk nnd IIX. II wns dosIgnod fo nIIow muIfIIo roufos bofwoon nny fwo oInfs nnd fo roufo nckofs of dnfn nround dnmngod roufors. Tho II hnd fo bo oon nnd Infform-Indoondonf. Thoro nro muIfIIo roufos bofwoon fwo oInfs, nnd sInco fho quIckosf nfh bofwoon fwo oInfs mny chnngo ovor fImo ns n funcfIon of nofwork frnffIc nnd ofhor fncfors, fho nckofs fhnf mnko u n nrfIcuInr dnfn sfronm mny nof nII fnko fho snmo roufo. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.ll

To Imrovo on fho bnsIc schomo, TCI wns Inyorod on fo of II fo gIvo onch ond of n connocfIon fho nbIIIfy fo ncknowIodgo rocoIf of II nckofs nnd roquosf rofrnnsmIssIon of Iosf or corrufod nckofs. TCP cnrrIos n fnIr nmounf of ovorhond. Thoroforo, If fho ordor of fho dnfn Isn'f nrfIcuInrIy Imorfnnf nnd If fho Ioss of IndIvIdunI nckofs won'f comIofoIy corruf fho dnfn sfronm, nckofs nro somofImos sonf wIfhouf fho gunrnnfoos fhnf TCI rovIdos. ThIs Is nccomIIshod fhrough fho uso of fho !I rofocoI. UDP Is nn unroIInbIo rofocoI fhnf doos nof gunrnnfoo fhnf nckofs wIII nrrIvo nf fhoIr dosfInnfIon or fhnf fhoy wIII nrrIvo In fho snmo ordor fhoy woro sonf. AIfhough fhIs wouId bo n robIom for usos such ns fIIo frnnsfor, If Is orfocfIy nccofnbIo for nIIcnfIons whoro fho Ioss of somo dnfn wouId go unnofIcod by fho ond usor. A numbor of ofhor rofocoIs cnn run on fo of II. Tho mosf commonIy roquosfod Is ICMI, fho Infornof ConfroI Mossngo IrofocoI, whIch usos rnw II dnfngrnms fo roIny orror mossngos bofwoon hosfs. Tho onIy rofocoIs Jnvn suorfs nro TCI nnd !I, nnd nIIcnfIon Inyor rofocoIs. IP Addvesses und omuIn Numes Ivory comufor on nn 1Pt4 netuork Is IdonfIfIod by n four-byfo numbor. ThIs Is normnIIy wrIffon In n doffod qund formnf IIko l99.l.32.90, whoro onch of fho four numbors Is ono unsIgnod byfo rnngIng In vnIuo from 0 fo 255. Ivory comufor nffnchod fo nn IIv4 nofwork hns n unIquo four-byfo nddross. Whon Jutu io trunomitteJ ncross fho nofwork, fho nckof's hondor IncIudos fho nddross of fho mnchIno for whIch fho nckof Is Infondod (fho dosfInnfIon nddross) nnd fho nddross of fho mnchIno fhnf sonf fho nckof (fho sourco nddross). Routero nIong fho wny chooso fho bosf roufo fo sond fho nckof nIong by InsocfIng fho dosfInnfIon nddross. Tho sourco nddross Is IncIudod so fho rocIIonf wIII know who fo roIy fo. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l2

A sIow frnnsIfIon Is undor wny fo 1Pt6, whIch wIII uso l6-byfo nddrossos. ThIs rovIdos onough II nddrossos fo IdonfIfy ovory orson, ovory comufor, nnd Indood ovory nfom on fho Innof. IIv6 nddrossos nro cusfomnrIIy wrIffon In oIghf bIocks of four hoxndocImnI dIgIfs sonrnfod by coIons, such ns IIC: IA98:?654:32l0: IIC: IA98:?654:32l0. !ondIng zoros do nof nood fo bo wrIffon. A doubIo coIon, nf mosf ono of whIch mny nonr In nny nddross, IndIcnfos muIfIIo zoro bIocks. In mireJ netuorko of IIv6 nnd IIv4, fho Insf four byfos of fho IIv6 nddross nro somofImos wrIffon ns nn IIv4 doffod qund nddross. Tho Domuin ume Syotem (DS) wns dovoIood fo frnnsInfo hosfnnmos fhnf humnns cnn romombor (IIko www.oroIIIy.com) Info numorIc Infornof nddrossos (IIko 208.20l.239.3?). Whon Jnvn rogrnms nccoss fho nofwork, fhoy nood fo rocoss bofh fhoso numorIc nddrossos nnd fhoIr corrosondIng hosfnnmos. Somo comufors, osocInIIy sorvors, hnvo fIxod nddrossos. Povts Modorn comufors do mnny dIfforonf fhIngs nf onco. ImnII noods fo bo sonrnfod from ITI roquosfs, whIch nood fo bo sonrnfod from wob frnffIc. ThIs Is nccomIIshod fhrough porto. Inch orf Is IdonfIfIod by n numbor bofwoon l nnd 65,535. Inch orf cnn bo nIIocnfod fo n nrfIcuInr sorvIco. HTTI usos Iorf 80. Whon Jutu io oent fo n wob sorvor on n nrfIcuInr mnchIno nf n nrfIcuInr II nddross, If Is nIso sonf fo n nrfIcuInr orf (usunIIy orf 80) on fhnf mnchIno. Tho receiter chocks onch nckof If soos for fho orf nnd sonds fho dnfn fo nny rogrnms fhnf nro IIsfonIng fo fho socIfIod orf. Iorf numbors bofwoon l nnd l,023 nro rosorvod for woII-known sorvIcos IIko fIngor, ITI, HTTI, nnd IMAI. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l3

WeII-known povt ussIgnments PvotocoI Povt PvotocoI Puvpose ocho ? TCI/!I Icho Is n fosf rofocoI usod fo vorIfy fhnf fwo mnchInos nro nbIo fo connocf by hnvIng ono ocho bnck fho ofhor's Inuf. dIscnrd 9 TCI/!I Iscnrd Is n Ioss usofuI fosf rofocoI In whIch nII dnfn rocoIvod by fho sorvor Is Ignorod. dnyfImo l3 TCI/!I IrovIdos nn ASCII rorosonfnfIon of fho curronf fImo on fho sorvor. ITI dnfn 20 TCI ITI usos fwo woII-known orfs. ThIs orf Is usod fo frnnsfor fIIos. ITI 2l TCI ThIs orf Is usod fo sond ITI commnnds IIko uf nnd gof. SSH 22 TCI !sod for oncryfod, romofo IogIns. foInof 23 TCI !sod for InforncfIvo, romofo commnnd-IIno sossIons. smf 25 TCI Tho SImIo MnII Trnnsfor IrofocoI Is usod fo sond omnII bofwoon mnchInos. fImo 3? TCI/!I A fImo sorvor rofurns fho numbor of soconds fhnf hnvo oInsod on fho sorvor sInco mIdnIghf, Jnnunry l, l900, ns n four-byfo, sIgnod, bIg-ondInn Infogor. whoIs 43 TCI A sImIo dIrocfory sorvIco for Infornof nofwork ndmInIsfrnfors. fIngor ?9 TCI A sorvIco fhnf rofurns InformnfIon nbouf n usor or usors on fho IocnI sysfom. HTTI 80 TCI Tho undorIyIng rofocoI of fho WorId WIdo Wob. IOI3 ll0 TCI Iosf OffIco IrofocoI VorsIon 3 Is n rofocoI for fho frnnsfor of nccumuInfod omnII from fho hosf fo sorndIcnIIy connocfod cIIonfs. TI ll9 TCI !sonof nows frnnsfor; moro formnIIy known ns fho "ofwork ows Trnnsfor IrofocoI". IMAI l43 TCI Infornof Mossngo Accoss IrofocoI Is n rofocoI for nccossIng mnIIboxos sforod on n sorvor. !MI !ogIsfry l099 TCI Tho rogIsfry sorvIco for Jnvn romofo objocfs. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l4

1.1.4 TH INTRNT Tho Infornof Is fho worId's Inrgosf II-bnsod nofwork. Inch comufor on fho Infornof hns nf Ionsf ono unIquo II nddross by whIch If cnn bo IdonfIfIod. Mosf of fhom nIso hnvo nf Ionsf ono nnmo fhnf mns fo fhnf II nddross. Tho Infornof Is nof fho onIy II-bnsod nofwork, buf If Is fho Inrgosf ono. Ofhor II nofworks nro cnIIod Infornofs wIfh n IIffIo I: for oxnmIo, n corornfo II nofwork fhnf Is nof connocfod fo fho Infornof. Infrnnof Is n curronf buzzword fhnf IoosoIy doscrIbos corornfo rncfIcos of uffIng Iofs of dnfn on InfornnI wob sorvors. If ovoryono Ickod fho Infornof nddrossos fhoy wnnfod nf rnndom, confIIcfs wouId nrIso nImosf ImmodInfoIy whon dIfforonf comufors showod u on fho Infornof wIfh fho snmo nddross. Intevnet Addvess CIusses To nvoId fhIs robIom, bIocks of IIv4 nddrossos nro nssIgnod fo Infornof SorvIco IrovIdors (ISIs) by fhoIr rogIonnI Infornof rogIsfry. ISI gIvos fhom n bIock of nddrossos. TrndIfIonnIIy, fhoso bIocks como In fhroo sIzos cnIIod CInss A, CInss I, nnd CInss C. A Cluoo C nddross bIock socIfIos fho fIrsf fhroo byfos of fho nddross; for oxnmIo, l99.l.32. ThIs nIIows room for 254 IndIvIdunI nddrossos from l99.l.32.l fo l99.l.32.254. A cluoo B nddross bIock onIy socIfIos fho fIrsf fwo byfos of fho nddrossos nn orgnnIznfIon mny uso; for Insfnnco, l6?.l. Thus, n cInss I nddross hns room for 65,024 dIfforonf hosfs (256 CInss C sIzo bIocks fImos 254 hosfs or CInss C bIock). A cluoo A nddross bIock onIy socIfIos fho fIrsf byfo of fho nddross rnngofor Insfnnco, l8nnd fhoroforo hns room for ovor l6 mIIIIon nodos. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l5

To moro offIcIonfIy nIIocnfo fho IImIfod nddross snco, CInssIoss Infor-omnIn !oufIng (C1DR) wns Invonfod. CI! mosfIy (fhough nof comIofoIy) roIncos fho whoIo A, I, C, , I nddrossIng schomo wIfh ono bnsod on n socIfIod numbors of rofIx bIfs. Thoso rofIxos nro gonornIIy wrIffon ns /nn, whoro nn Is n fwo-dIgIf numbor socIfyIng fho numbor of bIfs In fho nofwork orfIon of fho nddross. Tho numbor nffor fho / IndIcnfos fho numbor of fIxod rofIx bIfs. n /24 fIxos fho fIrsf 24 bIfs In fho nddross, IonvIng 8 bIfs nvnIInbIo fo dIsfInguIsh IndIvIdunI nodos. ThIs nIIows 256 nodos, nnd Is oquIvnIonf fo nn oId sfyIo CInss C. A /l9 fIxos l9 bIfs, IonvIng l3 for IndIvIdunI nodos wIfhIn fho nofwork. If's oquIvnIonf fo 32 sonrnfo CInss C nofworks or nn oIghfh of n CInss I. A /28, gonornIIy fho smnIIosf you'ro IIkoIy fo oncounfor In rncfIco, Ionvos onIy four bIfs for IdonfIfyIng IocnI nodos. SovornI nddross bIocks nnd nfforns nro socInI. AII IIv4 nddrossos fhnf bogIn wIfh l0., l?2.l6. fhrough l?2.3l., nnd l92.l68. nro doIIbornfoIy unnssIgnod. Thoy cnn bo usod on InfornnI nofworks, buf no hosf usIng nddrossos In fhoso bIocks Is nIIowod onfo fho gIobnI Infornof. Thoso non-routuble uJJreooeo nro usofuI for buIIdIng rIvnfo nofworks fhnf cnn'f bo soon from fho rosf of fho Infornof or for buIIdIng n Inrgo nofwork whon you'vo onIy boon nssIgnod n cInss C nddross bIock. IIv4 nddrossos bogInnIng wIfh l2? (mosf commonIy l2?.0.0.l) nIwnys monn fho locul loopbuck uJJreoo. Thnf Is, fhoso nddrossos nIwnys oInf fo fho IocnI comufor, no mnffor whIch comufor you'ro runnIng on. Tho hosfnnmo for fhIs nddross Is gonornIIy loculhoot. Netwovk Addvess TvunsIutIon Ior ronsons of bofh socurIfy nnd nddross snco consorvnfIon, mnny smnIIor nofworks, such ns fho nufhor's homo nofwork, uso netuork uJJreoo trunolution (AT). UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l6

Tho router wnfchos my oufgoIng nnd IncomIng connocfIons nnd ndjusfs fho nddrossos In fho II nckofs. Ior nn outgoing pucket, If chnngos fho sourco nddross fo fho roufor's oxfornnI nddross (2l6.254.85.?2 on my nofwork). Ior nn incoming pucket, If chnngos fho dosfInnfIon nddross fo ono of fho IocnI nddrossos, such ns l92.l68.254.l2. IIvewuIIs Tho hnrdwnro nnd soffwnro fhnf sIf bofwoon fho Infornof nnd fho IocnI nofwork, chockIng nII fho dnfn fhnf comos In or ouf fo mnko suro If's koshor, Is cnIIod n fireuull. Tho fIrownII Is offon nrf of fho roufor fhnf connocfs fho IocnI nofwork fo fho brondor Infornof nnd mny orform ofhor fnsks, such ns nofwork nddross frnnsInfIon. Thon ngnIn, fho fIrownII mny bo n sonrnfo mnchIno. Tho fIrownII Is reoponoible for InsocfIng onch nckof fhnf nssos Info or ouf of Ifs nofwork Inforfnco nnd nccofIng If or rojocfIng If nccordIng fo n sof of ruIos. IIIforIng Is usunIIy bnsod on nofwork nddrossos nnd orfs. Tho oxncf confIgurnfIon of n fIrownIIwhIch nckofs of dnfn nro nnd nro nof nIIowod fo nss fhroughdoonds on fho socurIfy noods of nn IndIvIdunI sIfo. Pvoy Sevvevs Iroxy sorvors nro roInfod fo fIrownIIs. If n fIrownII rovonfs hosfs on n nofwork from mnkIng dIrocf connocfIons fo fho oufsIdo worId, n roxy sorvor cnn ncf ns n go-bofwoon. Thus, n mnchIno fhnf Is rovonfod from connocfIng fo fho oxfornnI nofwork by n fIrownII wouId mnko n roquosf for n wob ngo from fho IocnI roxy sorvor Insfond of roquosfIng fho wob ngo dIrocfIy from fho romofo wob sorvor. Tho roxy sorvor wouId fhon roquosf fho ngo from fho wob sorvor nnd forwnrd fho rosonso bnck fo fho orIgInnI roquosfor. IroxIos cnn nIso bo usod for ITI sorvIcos nnd ofhor connocfIons. Ono of fho oecurity uJtuntugeo of usIng n roxy sorvor Is fhnf oxfornnI hosfs onIy fInd ouf nbouf fho roxy sorvor. Thoy do nof Ionrn fho nnmos nnd II nddrossos of fho InfornnI mnchInos, mnkIng If moro dIffIcuIf fo hnck Info InfornnI sysfoms. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l?

A roxy sorvor hns n dofnIIod undorsfnndIng of somo nIIcnfIon IovoI rofocoIs, such ns HTTI nnd ITI. Inckofs fhnf nss fhrough fho roxy sorvor cnn bo oxnmInod fo onsuro fhnf fhoy confnIn dnfn nrorInfo for fhoIr fyo. LuyereJ connectiono through u prory oerter Somo comnnIos nIIow IncomIng ITI buf dIsnIIow oufgoIng ITI so confIdonfInI dnfn cnnnof bo ns onsIIy smuggIod ouf of fho comnny. Iroxy sorvors cnn nIso bo usod fo ImIomonf locul cuching. Whon n fIIo Is roquosfod from n wob sorvor, fho roxy sorvor fIrsf chocks fo soo If fho fIIo Is In Ifs cncho. If fho file io in the cuche, fho roxy sorvos fho fIIo from fho cncho rnfhor fhnn from fho Infornof. If fho file io not in the cuche, fho roxy sorvor rofrIovos fho fIIo, forwnrds If fo fho roquosfor, nnd sforos If In fho cncho for fho noxf fImo If Is roquosfod. Tho bIggosf robIom wIfh roxy sorvors Is fhoIr InnbIIIfy fo coo wIfh nII buf n fow rofocoIs. ConornIIy osfnbIIshod rofocoIs IIko HTTI, ITI, nnd SMTI nro nIIowod fo nss fhrough, whIIo nowor rofocoIs IIko CnufoIIn nro nof. If's n nrfIcuInr JiouJtuntuge for Jnvn rogrnmmors bocnuso If IImIfs fho offocfIvonoss of cusfom rofocoIs. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l8

1.1.5 TH CIINT/SRVR MOI A cIIonf/sorvor nIIcnfIon fyIcnIIy sforos Inrgo qunnfIfIos of dnfn on nn oxonsIvo, hIgh-oworod sorvor whIIo mosf of fho rogrnm IogIc nnd fho usor-Inforfnco Is hnndIod by cIIonf soffwnro runnIng on roInfIvoIy chon orsonnI comufors. In mosf cnsos, n sorvor rImnrIIy sonds dnfn whIIo n cIIonf rImnrIIy rocoIvos If, buf If Is rnro for ono rogrnm fo sond or rocoIvo oxcIusIvoIy. A moro roIInbIo dIsfIncfIon Is fhnf n cIIonf InIfInfos n convorsnfIon whIIo n sorvor wnIfs for cIIonfs fo sfnrf convorsnfIons wIfh If. A cIIent/sevvev connectIon Somo sorvors rocoss nnd nnnIyzo fho dnfn boforo sondIng fho rosuIfs fo fho cIIonf. Such sorvors nro offon roforrod fo ns "nIIcnfIon sorvors" fo dIsfInguIsh fhom from fho moro common fIIo sorvors nnd dnfnbnso sorvors. A file or Jutubuoe oerter wIII rofrIovo InformnfIon nnd sond If fo n cIIonf, buf If won'f rocoss fhnf InformnfIon. In confrnsf, nn nIIcnfIon sorvor mIghf Iook nf nn ordor onfry dnfnbnso nnd gIvo fho cIIonfs roorfs nbouf monfhIy snIos fronds. An nIIcnfIon sorvor Is nof n sorvor fhnf sorvos fIIos fhnf hnon fo bo nIIcnfIons. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.l9

Web oertero IIko Ancho rosond fo roquosfs from wob cIIonfs IIko IIrofox. nfn Is sforod on fho wob sorvor nnd Is sonf ouf fo fho cIIonfs fhnf roquosf If. Wob sorvors fhnf uso CCI rogrnms doubIo ns nIIcnfIon nnd fIIo sorvors. FTP Is nn oIdor sorvIco fhnf fIfs fho cIIonf/sorvor modoI. ITI usos dIfforonf nIIcnfIon rofocoIs nnd dIfforonf soffwnro, buf Is sfIII sIIf Info ITI sorvors fhnf sond fIIos nnd ITI cIIonfs fhnf rocoIvo fIIos. Ior Insfnnco, In nofworkod gnmos, If sooms IIkoIy fhnf bofh Inyors wIII sond dnfn bnck nnd forfh roughIy oqunIIy. Thoso sorfs of connocfIons nro cnIIod peer-to-peer. Tho oors cnn communIcnfo wIfh onch ofhor fhrough nn InformodInfo sorvor rogrnm fhnf forwnrds dnfn from ono oor fo fho ofhor oors. 1.1.6 INTRNT STANARS Thoro nro mnny sfnndnrds orgnnIznfIons In fho worId, fho fwo fhnf roduco mosf of fho sfnndnrds roIovnnf fo nofwork rogrnmmIng nnd rofocoIs nro fho Infornof IngInoorIng Tnsk Iorco (IITI) nnd fho WorId WIdo Wob ConsorfIum (W3C). Tho 1ETF Is n roInfIvoIy InformnI, domocrnfIc body oon fo nrfIcInfIon by nny Inforosfod nrfy. Ifs sfnndnrds nro bnsod on "rough consonsus nnd runnIng codo" nnd fond fo foIIow rnfhor fhnn Iond ImIomonfnfIons. IITI sfnndnrds IncIudo TCI/II, MIMI, nnd SMTI. Tho W3C, by confrnsf, Is n vondor orgnnIznfIon, confroIIod by duos-nyIng mombor corornfIons, fhnf oxIIcIfIy oxcIudos nrfIcInfIon by IndIvIdunIs. Tho W3C frIos fo dofIno sfnndnrds In ndvnnco of ImIomonfnfIon. W3C sfnndnrds IncIudo HTTI, HTM!, nnd XM!. A) ITI RICs 1ETF sfnndnrds nnd nonr-sfnndnrds nro ubIIshod ns Infornof drnffs nnd roquosfs for commonfs (!ICs). !ICs nnd Infornof drnffs rnngo from InformnfIonnI UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.20

documonfs of gonornI Inforosf fo dofnIIod socIfIcnfIons of sfnndnrd Infornof rofocoIs IIko ITI. RFCs fhnf documonf n sfnndnrd or n roosod sfnndnrd nro ubIIshod onIy wIfh fho nrovnI of fho Infornof IngInoorIng SfoorIng Crou (IISC) of fho IITI. Ioforo somofhIng cnn bocomo nn IITI sfnndnrd, If musf ncfunIIy oxIsf nnd work. ThIs roquIromonf onsuros fhnf IITI sfnndnrds nro nf Ionsf fonsIbIo, unIIko fho sfnndnrds romuIgnfod by somo ofhor orgnnIznfIons. A uorking group mny bo formod undor fho nusIcos of fho IITI. ThIs workIng grou nffomfs fo documonf fho rofocoI In nn Infornof-rnff. Infornof-rnffs nro workIng documonfs nnd chnngo froquonfIy fo rofIocf oxorIonco wIfh fho rofocoI. Tho roosnI goos fhrough sIx sfnfos or mnfurIfy IovoIs ns If foIIows fho sfnndnrdIznfIon frnck: IxorImonfnI Iroosod sfnndnrd rnff sfnndnrd Sfnndnrd InformnfIonnI HIsforIc Tho erperimentul sfngo doos nof ImIy fhnf fho rofocoI Is nof soIId or fhnf If Is nof wIdoIy usod; unforfunnfoIy, fho sfnndnrds rocoss usunIIy Ings bohInd do fncfo nccofnnco of fho sfnndnrd. If fho oxorImonfnI sfnndnrd hoIds u woII In furfhor ronI worId fosfIng, fho IISC mny ndvnnco If fo fho sfnfus of roosod sfnndnrd. A propooeJ otunJurJ Is fnIrIy Iooso, nnd Is bnsod on fho oxorImonfnI work of ossIbIy ns IIffIo ns ono orgnnIznfIon. Chnngos mny sfIII bo mndo fo n rofocoI In fhIs sfngo. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.2l

Tho IISC mny rocommond fhnf n roosod sfnndnrd bo romofod fo n Jruft otunJurJ. A drnff sfnndnrd wIII robnbIy nof chnngo foo much boforo ovonfunI sfnndnrdIznfIon unIoss mnjor fInws nro found. Tho rImnry uroso of n drnff sfnndnrd Is fo cIonn u fho !IC fhnf documonfs fho rofocoI nnd mnko suro fho documonfnfIon conforms fo ncfunI rncfIco, rnfhor fhnn fo chnngo fho sfnndnrd IfsoIf. Whon n rofocoI comIofos fhIs, If bocomos nn offIcInI 1nternet otunJurJ. If Is nssIgnod nn ST numbor nnd Is ubIIshod ns nn ST In nddIfIon fo nn !IC. Somo !ICs fhnf do nof bocomo sfnndnrds nro consIdorod informutionul. Thoso IncIudo !ICs fhnf socIfy rofocoIs fhnf nro wIdoIy usod buf woron'f dovoIood wIfhIn fho normnI Infornof sfnndnrds frnck, nnd hnvon'f boon fhrough fho formnI sfnndnrdIznfIon rocoss. A rofocoI hns n roquIromonf IovoI. Tho ossIbIo roquIromonf IovoIs nro: ot recommenJeJ ShouId nof bo ImIomonfod by nnyono. LimiteJ uoe Mny hnvo fo bo ImIomonfod In corfnIn unusunI sIfunfIons buf won'f bo noodod by mosf hosfs. MnInIy fhoso nro oxorImonfnI rofocoIs. Electite Cnn bo ImIomonfod by nnyono who wnnfs fo uso fho rofocoI. Ior oxnmIo, !IC 2045, MuIfIuroso Infornof MnII IxfonsIons, Is n rnff IIocfIvo Sfnndnrd. RecommenJeJ ShouId bo ImIomonfod by Infornof hosfs fhnf don'f hnvo n socIfIc ronson nof fo ImIomonf If. Mosf rofocoIs fhnf you nro fnmIIInr wIfh (IIko TCI nnd !I, SMTI for omnII, ToInof for romofo IogIn, ofc.) nro rocommondod. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.22

RequireJ Musf bo ImIomonfod by nII Infornof hosfs. Thoro nro vory fow roquIrod rofocoIs. II IfsoIf Is ono (!IC ?9l), buf ovon rofocoIs ns Imorfnnf ns TCI or !I nro onIy rocommondod. A sfnndnrd Is onIy roquIrod If If Is nbsoIufoIy ossonfInI fo fho funcfIonIng of n hosf on fho Infornof. B) W3C RCOMMNATIONS AIfhough fho W3C sfnndnrdIznfIon rocoss Is sImIInr fo fho IITI rocoss (n sorIos of workIng drnffs hnshod ouf on mnIIIng IIsfs rosuIfIng In nn ovonfunI socIfIcnfIon), fho W3C Is n fundnmonfnIIy dIfforonf orgnnIznfIon. Tho W3C hns hnd consIdornbIy Ioss succoss In convIncIng vondors IIko ofscno nnd MIcrosoff fo fuIIy nnd consIsfonfIy ImIomonf Ifs sfnndnrds. Tho W3C hns fIvo bnsIc IovoIs of sfnndnrds: ote A nofo Is gonornIIy ono of fwo fhIngs: oIfhor nn unsoIIcIfod submIssIon by n W3C mombor (sImIInr fo nn IITI Infornof drnff) or rnndom musIngs by W3C sfnff or roInfod nrfIos fhnf do nof ncfunIIy doscrIbo n fuII roosnI (sImIInr fo nn IITI InformnfIonnI !IC). ofos wIII nof nocossnrIIy Iond fo fho formnfIon of n workIng grou or n W3C rocommondnfIon. Working Jrufto A workIng drnff Is n rofIocfIon of fho curronf fhInkIng of somo (nof nocossnrIIy nII) mombors of n workIng grou. If shouId ovonfunIIy Iond fo n roosod rocommondnfIon, buf by fho fImo If doos so If mny hnvo chnngod subsfnnfInIIy. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.23

CunJiJute recommenJution A cnndIdnfo rocommondnfIon IndIcnfos fhnf fho workIng drnff hns ronchod consonsus on nII mnjor Issuos nnd Is rondy for fhIrd-nrfy commonf nnd ImIomonfnfIons. If fho ImIomonfnfIons do nof uncovor nny obsfrucfIons, fho soc cnn bo romofod fo n roosod rocommondnfIon. PropooeJ recommenJution A roosod rocommondnfIon Is mosfIy comIofo nnd unIIkoIy fo undorgo moro fhnn mInor odIforInI chnngos. Tho mnIn uroso of n roosod rocommondnfIon Is fo work ouf bugs In fho socIfIcnfIon documonf rnfhor fhnn In fho undorIyIng fochnoIogy boIng documonfod. RecommenJution A rocommondnfIon Is fho hIghosf IovoI of W3C sfnndnrd. Howovor, fho W3C Is vory cnrofuI nof fo ncfunIIy cnII fhIs n "sfnndnrd" for fonr of runnIng nfouI of nnfIfrusf sfnfufos. Tho W3C doscrIbos n rocommondnfIon ns n "work fhnf rorosonfs consonsus wIfhIn W3C nnd hns fho Irocfor's sfnm of nrovnI. W3C consIdors fhnf fho Idons or fochnoIogy socIfIod by n !ocommondnfIon nro nrorInfo for wIdosrond doIoymonf nnd romofo W3C's mIssIon." 1.2 BASIC WB CONCPTS Tho Hypertert Trunofer Protocol (HTTI) Is n sfnndnrd fhnf dofInos how n wob cIIonf fnIks fo n sorvor nnd how dnfn Is frnnsforrod from fho sorvor bnck fo fho cIIonf. Tho nrchIfocfuro nnd dosIgn of fho HTTI rofocoI Is !orosonfnfIonnI Sfnfo Trnnsfor (!IST). HTTI cnn bo usod fo frnnsfor dnfn In ossonfInIIy nny formnf, from TIII Icfuros fo MIcrosoff Word documonfs fo Inso fIIos. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.24

Tho Wob's nnfIvo formnf Is fho Hyorfoxf Mnrku !nngungo (HTM!). HTM! Is n sImIo sfnndnrd for doscrIbIng fho somnnfIc vnIuo of foxfunI dnfn. HTML Is n "hyorfoxf mnrku Inngungo" bocnuso If IncIudos n wny fo socIfy IInks fo ofhor documonfs IdonfIfIod by !!!s. A !!! Is n wny fo unnmbIguousIy IdonfIfy fho IocnfIon of n rosourco on fho Infornof. 1.2.1 URIs A !nIform !osourco IdonfIfIor (!!I) Is n sfrIng of chnrncfors In n nrfIcuInr synfnx fhnf IdonfIfIos n rosourco. Tho rosourco IdonfIfIod mny bo n fIIo on n sorvor, buf If mny nIso bo nn omnII nddross, n nows mossngo, n book, n orson's nnmo, nn Infornof hosf, fho curronf sfock rIco of Sun MIcrosysfoms, or somofhIng oIso. An uboolute UR1 Is mndo u of n schomo for fho !!I nnd n schomo-socIfIc nrf, sonrnfod by n coIon, IIko fhIs: ecIene:ecIene-epecific-porI Tho synfnx of fho schomo-socIfIc nrf doonds on fho schomo boIng usod. Curronf schomos IncIudo: JoIo : Inso64-oncodod dnfn IncIudod dIrocfIy In n IInk; soo !IC 239? file : A fIIo on n IocnI dIsk fIp : An ITI sorvor IIIp : A WorId WIdo Wob sorvor usIng fho Hyorfoxf Trnnsfor IrofocoI gopIer : A Cohor sorvor noilIo : An omnII nddross neue : A !sonof nowsgrou IelneI : A connocfIon fo n ToInof-bnsod sorvIco urn : A !nIform !osourco nmo UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.25

Thoro Is no socIfIc synfnx fhnf nIIos fo fho schomo-socIfIc nrfs of nII !!Is. //ouIIoriI,/poII`quer, Tho uuthority purt of fho !!I nnmos fho nufhorIfy rosonsIbIo for rosoIvIn g fho rosf of fho !!I. Ior Insfnnco, fho !!I hff://www.Ioff.org/rfc/rfc2396.fxf hns fho schomo hff nnd fho nufhorIfy www.Ioff.org. ThIs monns fho sorvor nf www.Ioff.org Is rosonsIbIo for mnIng fho nfh /rfc/rfc2396.fxf fo n rosourco. ThIs !!I doos nof hnvo n quory nrf. Tho !!I hff://www.owoIIs.com/cgI-bIn/bIbIIo`Inkoy=62-l565928?09-0 hns fho schomo hff, fho nufhorIfy www.owoIIs.com, fho puth /bIbIIo, nnd fho query Inkoy=62-l565928?09-0. Tho !!I urn:Isbn: l565928?0 hns fho schomo urn buf doosn'f foIIow fho hIornrchIcnI //nufhorIfy/nfh`quory form for schomo-socIfIc nrfs. If the uuthority io un 1nternet hoot, ofIonnI usornnmos nnd orfs mny nIso bo rovIdod fo mnko fho nufhorIfy moro socIfIc. Ior oxnmIo, fho !!I ff://m3:m3cI43l98-n.nshvIIl.nc.homo.com:33/VnnHnIon-Jum.m3 hns fho nufhorIfy m3:m3cI43l98-n.nshvIIl.nc.homo.com:33. ThIs nufhorIfy hns fho usornnmo m3, fho nssword m3, fho hosf cI43l98-n.nshvIIl.nc.homo.com, nnd fho orf 33. If hns fho schomo ff nnd fho nfh /VnnHnIon-Jum.m3. PutL Tho nfh (whIch IncIudos Ifs InIfInI /) Is n sfrIng fhnf fho nufhorIfy cnn uso fo doformIno whIch rosourco Is IdonfIfIod. Ifforonf nufhorIfIos mny Inforrof fho snmo nfh fo rofor fo dIfforonf rosourcos. Tho nfh mny bo hIornrchIcnI, In whIch cnso fho IndIvIdunI nrfs nro sonrnfod by forwnrd sInshos, nnd fho . nnd .. oornfors nro usod fo nnvIgnfo fho hIornrchy. ScLeme Tho schomo nrf Is comosod of Ioworcnso Ioffors, dIgIfs, nnd fho Ius sIgn, orIod, nnd hyhon. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.26

Tho ofhor fhroo nrfs of n fyIcnI !!I (nufhorIfy, nfh, nnd quory) shouId onch bo comosod of fho ASCII nIhnnumorIc chnrncfors; fhnf Is, fho Ioffors A-Z, n-z, nnd fho dIgIfs 0-9. In nddIfIon, fho uncfunfIon chnrncfors - _ . ! ~ * ' mny nIso bo usod. AII ofhor chnrncfors, IncIudIng non-ASCII nIhnnumorIcs such ns nnd , shouId bo oscnod by n orconf sIgn () foIIowod by fho hoxndocImnI codo for fho chnrncfor. Ior Insfnnco, wouId bo oncodod ns Il. Note: Tho !!I nnd !!! socIfIcnfIons don'f ncfunIIy sny whnf chnrncfor sof shouId bo usod, whIch monns mosf soffwnro fonds fo uso fho IocnI dofnuIf chnrncfor sof. Thus, !!!s confnInIng non-ASCII chnrncfors nron'f vory InforoornbIo ncross dIfforonf Infforms nnd Inngungos. Work Is ongoIng fo dofIno InfornnfIonnIIzod !osourco IdonfIfIors (I!Is) fhnf cnn uso fho fuII rnngo of !nIcodo. Af fho fImo of fhIs wrIfIng, fho I!I drnff socIfIcnfIon IndIcnfos fhnf non-ASCII chnrncfors shouId bo oncodod by fIrsf convorfIng fhom fo !TI-8, fhon orconf-oscnIng onch byfo of fho !TI-8, ns socIfIod nbovo. Ior Insfnnco, fho Crook Ioffor Is !nIcodo codo oInf 3C0. In !TI-8, fhIs Ioffor Is oncodod ns fho fhroo byfos I0, A?, 80. Thus In n !!! If wouId bo oncodod ns I0A?80. A) URNs Thoro nro fwo fyos of !!Is: !nIform !osourco !ocnfors (!!!s) nnd !nIform !osourco nmos (!!s). A URL Is n oInfor fo n nrfIcuInr rosourco on fho Infornof nf n nrfIcuInr IocnfIon. Ior oxnmIo, hff://www.oroIIIy.com/cnfnIog/jnvnn3/ Is ono of sovornI !!!s for fho book Jnvn ofwork IrogrnmmIng. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.2?

A UR Is n nnmo for n nrfIcuInr rosourco buf wIfhouf roforonco fo n nrfIcuInr IocnfIon. Ior Insfnnco, urn:Isbn:l565928?09 Is n !!. Tho goul of URo Is fo hnndIo rosourcos fhnf nro mIrrorod In mnny dIfforonf IocnfIons or fhnf hnvo movod from ono sIfo fo nnofhor; fhoy IdonfIfy fho rosourco IfsoIf, nof fho Inco whoro fho rosourco IIvos. A !! hns fho gonornI form: urn: numeopuce: reoource_nume Tho numeopuce Is fho nnmo of n coIIocfIon of corfnIn kInds of rosourcos mnInfnInod by somo nufhorIfy. Tho reoource_nume Is fho nnmo of n rosourco wIfhIn fhnf coIIocfIon. Ior Insfnnco, fho !! urn:ISI:l56592485l IdonfIfIos n rosourco In fho ISI nnmosnco wIfh fho IdonfIfIor l56592485l. Tho oxncf synfnx of rosourco nnmos doonds on fho nnmosnco. Tho ISI nnmosnco oxocfs fo soo sfrIngs comosod of l0 or l3 chnrncfors, nII of whIch nro dIgIfswIfh fho sIngIo oxcofIon fhnf fho Insf chnrncfor mny bo fho Ioffor X (oIfhor uor- or Ioworcnso) Insfond. B) URIs A !!! IdonfIfIos fho IocnfIon of n rosourco on fho Infornof. If socIfIos fho rofocoI usod fo nccoss n sorvor (o.g., ITI, HTTI), fho nnmo of fho sorvor, nnd fho IocnfIon of n fIIo on fhnf sorvor. Tho synfnx of n !!! Is: protocol://uoernume"hootnume:port/puth/filenume?query#frugment Tho protocol Is nnofhor word for whnf wns cnIIod fho schomo of fho !!I. In n !!!, fho rofocoI nrf cnn bo fIIo, ff, hff, hffs, gohor, nows, foInof, wnIs, or vnrIous ofhor sfrIngs. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.28

Tho hootnume nrf of n !!! Is fho nnmo of fho sorvor fhnf rovIdos fho rosourco you wnnf, such ns www.oroIIIy.com or ufoIn.oIy.odu. If cnn nIso bo fho sorvor's II nddross, such ns 204.l48.40.9 or l28.238.3.2l. Tho uoernume Is nn ofIonnI usornnmo for fho sorvor. Tho port number Is nIso ofIonnI. If's nof nocossnry If fho sorvIco Is runnIng on Ifs dofnuIf orf (orf 80 for HTTI sorvors). Tho puth oInfs fo n nrfIcuInr dIrocfory on fho socIfIod sorvor. Tho nfh Is roInfIvo fo fho documonf roof of fho sorvor, nof nocossnrIIy fo fho roof of fho fIIosysfom on fho sorvor. Tho filenume oInfs fo n nrfIcuInr fIIo In fho dIrocfory socIfIod by fho nfh. If Is offon omIffodIn whIch cnso, If Is Ioff fo fho sorvor's dIscrofIon whnf fIIo, If nny, fo sond. Tho query otring rovIdos nddIfIonnI nrgumonfs for fho sorvor. If's commonIy usod onIy In hff !!!s, whoro If confnIns form dnfn for Inuf fo rogrnms runnIng on fho sorvor. Tho frugment roforoncos n nrfIcuInr nrf of fho romofo rosourco. If fho romofo rosourco Is HTM!, fho frngmonf IdonfIfIor nnmos nn nnchor In fho HTM! documonf. If fho romofo rosourco Is XM!, fho frngmonf IdonfIfIor Is nn XIoInfor. ReIutIve URIs A !!! mny InhorIf fho rofocoI, hosfnnmo, nnd nfh of Ifs nronf documonf (I.o., fho documonf In whIch If nonrs). !!!s fhnf nron'f comIofo buf InhorIf Iocos from fhoIr nronf nro cnIIod relutite URLo. In confrnsf, n comIofoIy socIfIod !!! Is cnIIod nn uboolute URL. In n roInfIvo !!!, nny Iocos fhnf nro mIssIng nro nssumod fo bo fho snmo ns fho corrosondIng Iocos from fho !!! of fho documonf In whIch fho !!! Is found.!oInfIvo !!!s hnvo n numbor of ndvnnfngos. IIrsfnnd Ionsf Imorfnnffhoy snvo n IIffIo fyIng. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.29

Moro ImorfnnfIy, roInfIvo !!!s nIIow n sIngIo documonf froo fo bo sorvod by muIfIIo rofocoIs: for Insfnnco, bofh ITI nnd HTTI. Tho HTTI mIghf bo usod for dIrocf surfIng, whIIo fho ITI couId bo usod for mIrrorIng fho sIfo. 1.2.2 HTMI, SGMI, und XMI HTML Is fho rImnry formnf usod for Wob documonfs. Idon of doscrIbIng n foxf's somnnfIcs rnfhor fhnn Ifs nonrnnco comos from nn oIdor sfnndnrd cnIIod fho Sfnndnrd ConornIIzod Mnrku !nngungo (SCM!). Sfnndnrd HTM! Is nn Insfnnco of SCM!. SCML nnd, by InhorIfnnco, HTM! nro bnsod on fho nofIon of dosIgn by monnIng rnfhor fhnn dosIgn by nonrnnco. Tho fngs usod fo mnrk u the tert ure cuoe-inoenoitite. Thus, Is fho snmo ns Is fho snmo ns Is fho snmo ns . Somo fngs hnvo n mnfchIng ond-fng fo dofIno n rogIon of foxf. An ond-fng Is fho snmo ns fho sfnrf-fng, oxcof fhnf fho oonIng nngIo brnckof Is foIIowod by n /. Ior oxnmIo: fhIs foxf Is sfrong; fhIs foxf Is omhnsIzod. Tho onfIro foxf from fho bogInnIng of fho sfnrf-fng fo fho ond of fho ond-fng Is cnIIod nn element. Thus, fhIs foxf Is sfrong Is n ST!OC oIomonf.HTM! oIomonfs mny nosf buf fhoy ohoulJ not oterlup. Tho fIrsf IIno In fho foIIowIng oxnmIo Is sfnndnrd-conformIng. Tho socond IIno Is nof, fhough mnny browsors nccof If nonofhoIoss: Jnck nnd JIII wonf u fho hIII (Correct) fo fofch n nII of wnfor (Wrong) Tho fng nnd mosf ofhor nrngrnh-IovoI fngs mny hnvo nn A!IC nffrIbufo fhnf snys whofhor fho hondor shouId bo conforod, Ioff-nIIgnod, or rIghf-nIIgnod. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.30

Ior oxnmIo: ThIs Is n conforod Hl hondIng Tho vnIuo of nn nffrIbufo mny bo oncIosod In doubIo or sIngIo quofos. Tho curronf sfnndnrd Is HTM! 4.0, mosf of whIch Is suorfod by curronf wob browsors, wIfh occnsIonnI oxcofIons. Tho fngnro nIIowod buf dorocnfod In HTM! 4.0. HTM! 4.0 mny bo fho ond of fho IIno, nsIdo from mInor fIxos. Tho W3C hns docrood fhnf HTM! Is goffIng foo buIky fo Inyor moro fonfuros on fo of. Tngs nro sof off by < nnd >. AffrIbufos nro oncIosod In quofnfIon mnrks, nnd so forfh. A sfyIoshoof Is usod fo doscrIbo how onch of fho Ifoms shouId bo dIsInyod. XML hns nnofhor ndvnnfngo ovor HTM!. HTM! cnn bo quIfo sIoy. IIomonfs nro oonod buf nof cIosod. AffrIbufo vnIuos mny or mny nof bo oncIosod In quofos. Tho quofos mny or mny nof bo rosonf. XM! fIghfons nII fhIs u. An XM! documonf mny hnvo n ocumonf Tyo ofInIfIon (T), whIch cnn Imoso nddIfIonnI consfrnInfs on vnIId documonfs. Ior oxnmIo, n T mny roquIro fhnf ovory I!O!CT oIomonf confnIn oxncfIy ono AMI oIomonf. ThIs hns n numbor of ndvnnfngos, buf fho koy ono horo Is fhnf XM! documonfs nro fnr onsIor fo nrso fhnn HTM! documonfs. XM! cnn bo usod bofh for uro XM! ngos nnd for omboddIng now kInds of confonf In HTM! nnd XHTM!. SMI!, fho SynchronIzod MuIfImodIn InfogrnfIon !nngungo, Is nn XM! nIIcnfIon for IncIudIng fImod muIfImodIn such ns sIIdo shows nnd subfIfIod vIdoos on wob ngos. 1.2.3 HTTP HTTI Is fho sfnndnrd rofocoI for communIcnfIon bofwoon wob browsors nnd wob sorvors. HTTI socIfIos how n cIIonf nnd sorvor osfnbIIsh n connocfIon, how fho cIIonf roquosfs dnfn from fho sorvor, how fho sorvor rosonds fo fhnf roquosf, nnd fInnIIy, how fho connocfIon Is cIosod. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.3l

Ior onch roquosf from cIIonf fo sorvor, fhoro Is n soquonco of four sfos: Muking the connection Tho cIIonf osfnbIIshos n TCI connocfIon fo fho sorvor on orf 80, by dofnuIf; ofhor orfs mny bo socIfIod In fho !!!. Muking u requeot Tho cIIonf sonds n mossngo fo fho sorvor roquosfIng fho ngo nf n socIfIod !!!. Tho formnf of fhIs roquosf Is fyIcnIIy somofhIng IIko: CIT /Indox.hfmI HTTI/l.0 CIT socIfIos fho oornfIon boIng roquosfod. Tho oornfIon roquosfod horo Is for fho sorvor fo rofurn n rorosonfnfIon of n rosourco. /Indox.hfmI Is n roInfIvo !!! fhnf IdonfIfIos fho rosourco roquosfod from fho sorvor. AIfhough fho CIT IIno Is nII fhnf Is roquIrod, n cIIonf roquosf cnn IncIudo ofhor InformnfIon ns woII. ThIs fnkos fho foIIowIng form: Ke,uorJ: Volue Tho mosf common such koyword Is Accof, whIch foIIs fho sorvor whnf kInds of dnfn fho cIIonf cnn hnndIo (fhough sorvors offon Ignoro fhIs). Ior oxnmIo, fho foIIowIng IIno snys fhnf fho cIIonf cnn hnndIo four MIMI modIn fyos, corrosondIng fo HTM! documonfs, InIn foxf, nnd JIIC nnd CII Imngos: Accof: foxf/hfmI, foxf/InIn, Imngo/gIf, Imngo/jog The reoponoe Tho sorvor sonds n rosonso fo fho cIIonf. Tho rosonso bogIns wIfh n rosonso codo, foIIowod by n hondor fuII of mofndnfn, n bInnk IIno, nnd fho roquosfod documonf or nn orror mossngo. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.32

Clooing the connection IIfhor fho cIIonf or fho sorvor or bofh cIoso fho connocfIon. Thus, n sonrnfo nofwork connocfIon Is usod for onch roquosf. If fho cIIonf roconnocfs, fho sorvor rofnIns no momory of fho rovIous connocfIon or Ifs rosuIfs. A rofocoI fhnf rofnIns no momory of nsf roquosfs Is cnIIod sfnfoIoss; In confrnsf, n sfnfofuI rofocoI such ns ITI cnn rocoss mnny roquosfs boforo fho connocfIon Is cIosod. Response code MeunIng 400 Ind !oquosf Tho cIIonf roquosf fo fho sorvor usod Imroor synfnx. ThIs Is rnfhor unusunI, nIfhough If Is IIkoIy fo hnon If you'ro wrIfIng nnd dobuggIng n cIIonf. 40l !nnufhorIzod AufhorIznfIon, gonornIIy usornnmo nnd nssword confroIIod, Is roquIrod fo nccoss fhIs ngo. IIfhor fho usornnmo nnd nssword hnvo nof yof boon rosonfod or fho usornnmo nnd nssword nro InvnIId. 403 IorbIddon Tho sorvor undorsfood fho roquosf buf Is doIIbornfoIy rofusIng fo rocoss If. AufhorIznfIon wIII nof hoI. Ono ronson fhIs occurs Is fhnf fho cIIonf nsks for n dIrocfory IIsfIng buf fho sorvor Is nof confIgurod fo rovIdo If. 404 of Iound ThIs mosf common orror rosonso IndIcnfos fhnf fho sorvor cnnnof fInd fho roquosfod ngo. If mny IndIcnfo n bnd IInk, n ngo fhnf hns movod wIfh no forwnrdIng nddross, n mIsfyod !!!, or somofhIng sImIInr. 50l of ImIomonfod Tho sorvor doos nof hnvo fho fonfuro fhnf Is noodod fo fuIfIII fhIs roquosf. A sorvor fhnf cnnnof hnndIo IOST roquosfs mIghf sond fhIs rosonso fo n cIIonf fhnf frIod fo IOST form dnfn fo If. 502 Ind Cnfowny ThIs rosonso Is nIIcnbIo onIy fo sorvors fhnf ncf ns roxIos or gnfownys. If IndIcnfos fhnf fho roxy rocoIvod nn InvnIId rosonso from n sorvor If wns connocfIng fo In nn offorf fo fuIfIII fho roquosf. 503 SorvIco !nnvnIInbIo Tho sorvor Is fomornrIIy unnbIo fo hnndIo fho roquosf, orhns ns n rosuIf of ovorIondIng or mnInfonnnco. HTTI l.l moro fhnn doubIos fho numbor of rosonsos. Howovor, n rosonso codo from 200 fo 299 nIwnys IndIcnfos succoss, n rosonso codo from 300 fo 399 nIwnys IndIcnfos rodIrocfIon, ono from 400 fo 499 nIwnys IndIcnfos n cIIonf orror, nnd ono from 500 fo 599 IndIcnfos n sorvor orror. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.33

HTTI l.0 Is documonfod In fho InformnfIonnI !IC l945; If Is nof nn offIcInI Infornof sfnndnrd bocnuso If wns rImnrIIy dovoIood oufsIdo fho IITI by onrIy browsor nnd sorvor vondors. HTTI l.l Is n roosod sfnndnrd boIng dovoIood by fho W3C nnd fho HTTI workIng grou of fho IITI. If rovIdos for much moro fIoxIbIo nnd oworfuI communIcnfIon bofwoon fho cIIonf nnd fho sorvor. If's nIso n Iof moro scnInbIo. If's documonfod In !IC 26l6. Tho rImnry Imrovomonf In HTTI l.l Is connocfIon rouso. HTTI l.0 oons n now connocfIon for ovory roquosf. 1.2.4 MIM MIA TYPS MIMI Is nn oon sfnndnrd for sondIng muIfInrf, muIfImodIn dnfn fhrough Infornof omnII. Tho dnfn mny bo bInnry, or If mny uso muIfIIo ASCII nnd non-ASCII chnrncfor sofs. AIfhough MIMI wns orIgInnIIy Infondod jusf for omnII, If hns bocomo n wIdoIy usod fochnIquo fo doscrIbo n fIIo's confonfs so fhnf cIIonf soffwnro cnn foII fho dIfforonco bofwoon dIfforonf kInds of dnfn. MIMI suorfs moro fhnn l00 rodofInod fyos of confonf. Confonf fyos nro cInssIfIod nf fwo IovoIs: n fyo nnd n subfyo. Tho fyo shows vory gonornIIy whnf kInd of dnfn Is confnInod: Is If n Icfuro, foxf, or movIo` Tho subfyo IdonfIfIos fho socIfIc fyo of dnfn: CII Imngo, JIIC Imngo, TIII Imngo. Tho confonf fyo for n CII Imngo Is Imngo/gIf; fho fyo Is Imngo, nnd fho subfyo Is gIf. Mosf wob sorvors nnd cIIonfs undorsfnnd nf Ionsf fwo MIMI foxf confonf fyos, foxf/hfmI nnd foxf/InIn, nnd fwo Imngo formnfs, Imngo/gIf nnd Imngo/jog. A MIMI-comIInnf rogrnm Is nof roquIrod fo undorsfnnd nII fhoso dIfforonf fyos of dnfn; If jusf noods fo rocognIzo whnf If cnn nnd cnnnof hnndIo. MIMI nIIows you fo dofIno nddIfIonnI nonsfnndnrd subfyos by usIng fho rofIx x-. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.34

Ior oxnmIo, fho confonf fyo nIIcnfIon/x-fox hns fho MIMI fyo nIIcnfIon nnd fho nonsfnndnrd subfyo x-fox for n ToX documonf. Thoso x-fyos nro nof gunrnnfood fo bo undorsfood by nny rogrnm ofhor fhnn fho ono fhnf cronfod fhom. Type Subtype escvIptIon foxf Tho documonf rorosonfs rInfnbIo foxf. css A CnscndIng SfyIo Shoof usod for HTM! nnd XM!. hfmI Hyorfoxf Mnrku !nngungo ns usod by wob browsors. InIn ThIs Is suosod fo ImIy rnw ASCII foxf. muIfInrf MuIfInrf MIMI mossngos oncodo sovornI dIfforonf fIIos Info ono mossngo. mIxod SovornI mossngo nrfs Infondod for soquonfInI vIowIng. sIgnod Ono nrf for fho body of fho mossngo nnd ono nrf for fho dIgIfnI sIgnnfuro. roInfod Comound documonfs formod by nggrognfIng sovornI smnIIor nrfs. mossngo An omnII mossngo. hff An HTTI l.l roquosf from n wob cIIonf fo n wob sorvor. Imngo Two-dImonsIonnI Icfuros. gIf A CrnhIcs Inforchnngo Iormnf Imngo. jog Tho JoInf IhofogrnhIc Ixorfs Crou fIIo formnf for bIfmnod Imngos wIfh Iossy comrossIon. nudIo Sound. bnsIc 8-bIf IS -Inw oncodod nudIo wIfh n sIngIo chnnnoI nnd n snmIo rnfo of oIghf kIIohorfz. ThIs Is fho formnf usod by .nu nnd .enJ fIIos nnd suorfod by fho jnvn.nIof.AudIoCII cInss. 1.2.5 SRVR-SI PROGRAMS Mnny wob ngos nro nof sorvod from sfnfIc fIIos on fho hnrd drIvo. Tho sorvor gonornfos fhom dynnmIcnIIy fo moof usor roquosfs. UNIT 1: IUNAMNTAIS WB TCHNOIOGY TLunguveI Muvugun l.35

Tho confonf mny bo uIIod from n dnfnbnso or gonornfod nIgorIfhmIcnIIy by n rogrnm. Indood, fho ncfunI ngo doIIvorod fo fho cIIonf mny confnIn dnfn combInod from sovornI dIfforonf sourcos. In Jnvn, such sorvor-sIdo rogrnms nro offon wrIffon usIng sorvIofs or Jnvn Sorvor Ingos (JSI). Ono ndvnnfngo fo HTTI Is fhnf If ronIIy doosn'f mnffor how fho ofhor sIdo of fho connocfIon Is wrIffon, ns Iong ns If sonks fho snmo bnsIc HTTI rofocoI. Tho oimpleot oerter-oiJe progrumo run wIfhouf nny Inuf from fho usor. Irom fho vIowoInf of fho cIIonf, fhoso rogrnms nro nccossod IIko nny ofhor wob ngo nnd nron'f of much concorn fo fhIs book. Tho Jifference bofwoon n wob ngo roducod by n rogrnm fhnf fnkos no Inuf nnd n wob ngo wrIffon In sfnfIc HTM! Is nII on fho sorvor sIdo. Whon wrIfIng cIIonfs, you don'f nood fo know or cnro whofhor fho wob sorvor Is foodIng you n fIIo or fho oufuf of somo rogrnm If rnn. HTTI rovIdos n sfnndnrd, woII undorsfood nnd woII suorfod monns for Jnvn nIofs nnd nIIcnfIons fo fnIk fo romofo sysfoms; fhoroforo, I wIII covor how fo uso Jnvn fo bofh rocoIvo nnd sond dnfn fo fho sorvor. Thoro nro other uuyo for Jutu progrumo to tulk to oertero, IncIudIng !omofo Mofhod InvocnfIon (!MI) nnd SOAI. Howovor, !MI Is sIow nnd SOAI Is quIfo comIox.