numerous新网dns

FORNEWBIES,EXPERTS&everyoneinbetweenDNSTableofContentsChapter1Chapter2:Chapter3:Chapter4:Chapter5:Chapter6:Chapter7:Chapter8:Chapter9:Chapter10:Chapter11:WhatisDNSWhatisaDNSQueryWhatisaDNSServerMisconceptionsDomainRegistrarvs.
DNSHostHowdoOutagesHappenWhyOutsourceWhatisDNSFailoverYourBackupPlanEveryIndustryNeedsDNSAboutUsWhatisDNSCHAPTER1AmericansusetheInternet.
Whilethatmightsoundprettyaverage,let'scomparethattothewholeplanetwhereonly4in10peopleusetheInternet.
Withallthisinmind,you'dthinkthatAmericansshouldbeprettytechsavvy,rightAndyet,only0.
003%ofAmericans*knowthatDNSisthereasontheInternetcontinuestoexistover30yearslater.
Prettyheavystuff,sowhydon'ttheother997outof1000peopleknowwhatthisamazingsystemisDNSgetstakenforgranted,becauseit'snotsomethingmostpeopleseewhentheyusetheInternet.
SowhatisthisproverbialgluethatholdstheInternettogetherFirstweneedtounderstandthattheInternetisessentiallyanetworkofcomputersthatconnecttoeachother.
Inorderforcomputerstofindeachother,theyneedacommonlanguage.
Inthebeginning,websurfersconnectedtoothercomputers(orwebsites)usinglongseriesofnumbers(IPaddresses)todescribethemselves.
Thisbecametroublesomeveryquicklybecausenoonecouldrememberallthoselongnumbers,sotheearly"fathersandmothers"oftheInternetdevelopedasystemtoattributeadomainnametoeachoftheseIPaddresses,entertheDomainNameSystem,orDNSforshort.
8in10Hi!
Mynameis10.
100.
200.
201YouexpectmetorememberthatPage2DNSforNewbies*basedonapollWhatisaDNSqueryCHAPTER2whatdoesthishavetodowithyouwantingtocheckthelatestcatvideoyourfriendtaggedyouinonFacebookWhenyoutypefacebook.
comintoyourbrowser,you'reactuallysendingoutaquery.
Yourcomputerdoesn'tknowwherefacebook.
comis,soithastoaskothercomputers,tolearnwherefacebook.
comis.
ButThinkbacktothedayswherewedidn'thavecellphonesandhadtousephonebookstocallpeople.
DNSisbasicallythephonebookoftheInternet!
ItstoresalltheIPaddresses(phonenumbers)anddomainnames(people,places,andbusinesses).
SayyouneedaDNSprovider,you'daskyourself"what'sthephonenumberforDNSMadeEasy"inanutshellthat'syourquery.
IntermsofDNS,yourqueryisasking"what'stheIPaddressfordnsmadeeasy.
com"SimplerightNowthisiswhereitgetsalittlemorecomplicated.
ThedomaininquestionhastobeaFullyQualifiedDomainName(FQDN),whichistheproperlyformattednameforadomain.
Thatmeansthatthedomainhasbothahostnameandadomainname.
Let'ssaywe'retryingtoreachDNSMadeEasymailservers,whicharehypotheticallylocatedatmail.
dnsmadeeasy.
comThehostnamewouldbe:mail.
Thedomainname:dnsmadeeasy.
comThequerywouldbe:mail.
dnsmadeeasy.
comTheresponsewouldbe:10.
200.
300.
201Page4DNSforNewbiesWhatisaDNSserverCHAPTER3BeforewegetintohowthesequeriestraveltheglobetryingtofindthatpeskyIPaddress,wefirstneedtounderstandwhataDNSserveris.
RememberthoseIPaddressesanddomainnamesweweretalkingaboutaminuteagoThesenumbersandnameshadtobestoredsomewherethatwasaccessibletotheentireInternet,sothat'swhenthefirstDNSserverwasbuilt.
Wait!
Simplyput,aDNSserverisacomputer(actuallythereareabunchofthesebutwecangettothatlater)thatholdspartsofthedatabasethatcontainsalltheIPaddressesandtheircorrespondingdomainnamesforpartsoftheInternet.
Whenyoutypeawebsiteintoyourbrowser,normallyyou'llbeconnectedtoyourdesiredpagewithinafewmilliseconds.
Thismakesalotofpeoplethinkthattherearen'tthatmanystepsorjumpsbetweenyourcomputerandtheserverthathostsyourdesiredwebsite.
Wrong!
Yourquerywillenduptakinghundredsofdifferentjumpsinbetween,andthenishastocomeallthewaybacktoyourcomputer.
Solet'sbreakitdown.
.
.
Page6DNSforNewbieswewanttovisitSaydnsmadeeasy.
com.
First,wehavetogoallthewaybacktotherootnameservers.
Theseserversarereallyspecial,becausetheyholdallofthedomainnamesandtheircorrespondingIPaddressestheDNSMadeEasyblog,whichisfoundat:social.
dnsmadeeasy.
comUsingtheDomainNamesystem,we'dlookuptherecordbybreakingdowntheaddresspiecebypiece.
Onceyou'vefoundtheIPaddressforyourdomain,thislittlepieceofinformationhastocomebacktoyourbrowserbeforeyou'refinallyconnected.
That'salotofstuffgoingoninjustacouplemilliseconds.
Toputthisinperspective,DNSMadeEasyprovidestheirclientswithsub30msresolutiontimesinallmajormarkets.
That'slessthanhalfthetimeittakestoblinkyoureye.
ThenweasktheCOMtopleveldomain(TLD)nameserversthathandleallthetrafficforsitesendingin.
comFromhere,the.
comnameserversidentifywhatnameserversdnsmadeeasy.
comisaresponsibleforFinally,theauthoritativeserversfordnsmadeeasy.
comrespondwiththeappropriateIPaddressforsocial.
dnsmadeeasy.
comsocial.
Page7DNSforNewbiesMisconceptionsCHAPTER4queriesthrough:RecursiveDNSServers(orCachingServers,soundslike"cashing")andAuthoritativeServers(whatDNSMadeEasyprovides).
Inanutshell,AuthoritativeDNSserversstorethe"maps"ofyourdomainnamestoIPaddresses.
ThisdomainnametoIPmappingisusuallyconfiguredbysystemadministrators.
ApersonthatisvisitingwebsitesasksRecursiveDNSserversforthelookups.
RecursiveDNSserversthanaskthenecessaryAuthoritativeNameServerfortheanswer.
ThentheRecursivenameserverwillgivethisanswertothepersonneedingtheinformation.
RecursiveserversaretheworkhorsesintheDNSlookupprocess.
TheyoftenhavetomakenumerousDNSlookupsinordertorespondwiththeproperIPforthequeryingclient.
ThesekindsofserversaretypicallymanagedbyanISP(InternetServiceProvider)orspecialtyresolvingDNSproviders.
Forexample:GooglerunstheirownpublicrecursiveDNSservers.
Weactuallyhaveagreatvideothatbreaksallthisdownatlearndns.
comTherePage9DNSforNewbiesaretwodifferentkindsofDNSserversthatyou'llrunyourRecursiveServerQueryingClientAuthoritativeServeradomainname,atsomepointyouwillneedWebrieflytalkedabouttherootnameserversearlier,whicharetheoriginalserversthatholdallofthedomainnamesandtheircorrespondingIPaddresses.
TherootserversareatthetopoftheproverbialDNStree.
TheyknowexactlywhichIPaddressesoftheauthoritativeserversaretheonesthathandleDNSqueriesforTopLevelDomains(TLD)like.
com.
IfyouowntouseanauthoritativeDNSservertomapyourdomainnamestoanIPaddress.
ThisisonlydoneonanAuthoritativeDNSserver.
AuthoritativeDNSserversareconfiguredinahierarchicalstructure.
Everythingstartswiththedotrootnameservers(likewediscussedearlier).
TheseauthoritativenameserversknowwheretofindthenextlevelsetinthehierarchysuchasTopLevelDomains.
Page10DNSforNewbiesThesearecalledrecursiveserversbecausetheyrecursethroughthehierarchicalDNStreefromtoptobottomuntiltheyhittheauthoritativeserverforthedomaininquestion.
Mostofthetime,recursiveDNSserversareactuallycachingrecursiveDNSservers.
ThismeanstheystorethemapsofURLstoIPsforaspecifiedamountoftime(knownastheTTLortimetolive).
Thismeanstheydon'thavetorepeatedlysendthesamequeriestothosesameauthoritativeservers,savingtheuseralotoftime.
Recursivenameserveronlyknowswheretofindtherootnameservers(dot).
Basedupeachlevelofnameserversknowingwherethenextlevelisinthehierarchy,theansweriseventuallyfound.
wherecanIfindthedomain'sauthoritativeserverwhat'stheIPaddressfortheauthoritativeserversforthe.
comTLDThenitgoestotheauthoritativeserverdesignatedas.
comFirsttherecursiveserverhastoasktherootdomainserversBacktowhatweweretalkingaboutearlier,let'ssaythatyourrecursiveDNSserverdoesn'thaveanyinformationcached.
WhatstepswouldtherecursiveservertaketofindtheIPaddressforsaiddomainPage11DNSforNewbieswherecanIfindmydomain'sauthoritativeserverDNSRegistervs.
HostCHAPTER5biggestmisconceptionsourusersfaceisstrugglingtounderstandthedifferencebetweenadomainregistrarandaDNShost.
Understandingthedifferenceiscrucialtomaintainingareliableandfastwebsitethat'savailabletoallofyourusers.
Let'sstartwiththebarebones:adomainregistraroffersservicesthatallowyoutopickadomainnameandregisterittoanIPaddress.
Thisisthefirststepyoutakewhenyouwanttobuildawebsite.
You'llrememberfromearlier,yourdomainname,likewww.
dnsmadeeasy.
com,isessentiallythefaceofyourIPaddress,123.
45.
678.
90.
OneoftheWhenyouregisteradomainname,youhavetogothroughaDNSregistrar.
Thesecompaniesoftendealdirectlywiththeregistryoperatorswhocontrolthemasterlistofalldomainnames.
TheseregistriesaremanagedbyIANA(InternationalAssignedNumbersAuthority),whichisadepartmentofICANN,anonprofitorganizationsthatrunstherootzonemanagementintheDomainNameSystem.
Mosttimes,youwon'tactuallydealwithadomainregistrardirectly;ratheryouenduppurchasingadomainnamethroughaWebHostingProvider.
Thesecompaniesdoalltheworkforyouandregisteryourdomainthroughtheregistriesallonyourbehalf.
.
.
butwe'llgetmoreintothisinaminute.
Wheneveryouruna"whois"command,oranonlineinterfacetothewhoisdata,you'reactuallyqueryingthedomainnameregistry.
DidyouknowPage13DNSforNewbieswhat'saDNShostOnceyou'vepurchasedyourdomainname,youhavetotellitwhichdomainnameserverswillbeauthoritativeforthatdomain.
ADNShostingproviderhoststheseservers,whichauthoritativelyrespondforyourdomain.
SometimesdomainregistriesalsoofferDNShosting,howeverthetwoservicesshouldneverbeconfused.
BeforewegodeeperintowhataDNShostdoes,weneedtoclearupthedifferentkindsofcompaniesthatofferDNShosting.
SothenToooftenpeopleresorttousingtheirwebhost'sDNSservicesbecausethey'reofferedasanadd-onorincludedwiththewebhostingservices.
Thistendstoconfusemostpeople;becausetheyendupthinkingthetwoareoneinthesame.
Inanutshell,webhostingisessentiallythespacewhereyourwebsitefilesarestored.
WhileDNShostingiswhatconnectsuserstothesiteandkeepsthedomainonline.
WhydoesallthismatterWhenyou'redecidinghowyouwanttohostyourDNS,youneedtobesureyouunderstandthedifferencesbetweenthedifferentkindsofhosts.
Yourdecisioncouldeitherkeepyoursiteonline100%ofthetimeatalowcost,orknockyouofflineandcostyouthousandsinmaintenanceandcleanup.
DNSistheend-all-be-allofyoursite'swebpresence.
Withoutit,noonewouldbeabletoaccessyourcontent.
DedicatedDNShostingproviderstendtohavefasterandmorereliableinfrastructure,designedfromtheground-upforhostingDNSquerytrafficandnothingelse.
DomainregistrarsthatofferDNShostingasanadditionalserviceWebhostingprovidersthatofferDNShostingasanadditionalserviceDedicatedDNShostingcompanies(that'salltheydo)In-houseDNShostingwhichisbasicallylikehavingyourownprivateDNShostPage14DNSforNewbiesHowdoOutagesHappenCHAPTER6toawebsiteandgottenanerrormessagethatsaid,"DNShostnotresolved"or"hostnotresolvable"ThisisbecauseyourDNShostisnotreachable.
Itcouldbethey'resufferinganoutage,ornetworkerror,notreliable,anetworkadminaccidentlydeletedarecord.
.
.
oraDDoSattack.
Prettymuchwhat'shappeningistheincomingtrafficissocongested,itslowstoacrawl.
Orinsomecases,thesitewillbeknockedcompletelyoffline.
Oftentimesit'stheresultofaDDoSattack(distributed-denial-of-serviceattack),whichisthedisruptionorabolitionofservicesofahostconnectedtotheInternet.
It'samouthful,butlet'sbreakitdownalittlemorewitharelatableexample.
Thinkoftheseconnectionsbetweentheinternetandyoursitelikehighways.
SayyoursiteisconnectedtotheWorldWideWebviaatwo-lanehighway.
NowwhatifyoursitegoesviralandyougetmillionsofpeoplespeedingtowardsyourwebsiteThemorepopularyouget,themoreeyeballsyouhaveonyoursite.
Thiscanattractbothpotentialcustomersandattackers.
ThemostcunningattacksuseDDoSEvergonePage16DNSforNewbiesattackswhichbasicallysendfloodsoftrafficatyoursite,butmakesitappearasifmanydifferentcomputersaresendingthetraffic.
Thismakesidentifyinganattackevenharder,becauseitcanappeartobenormalvisitors.
Ifwethinkofitlikeahighway,basicallyaDDoSattackmimicswhatrushhourwouldlooklike,inevitablybringingyoursitetoagridlock.
ofattacksareorchestratedfloodsofpackets(whichyou'llrememberfromearlierarelikethequeriesyousendtoaDNSservertoaccessawebsite'sIPaddress).
Yoursite'snameserverscanonlyhandleafiniteamountofDNSrequestsorPPS(packetspersecond)beforetheyfail.
ADNShostingprovider,likeDNSMadeEasy,solvesthisproblembysettinguphundredsofnameserversworldwideonanAnycastnetwork.
It'sprettymuchlikehavingamajorinterstatehighwaysystemthatconsistsofmanydifferenthighwaynetworksspreadacrossalargearea.
ThesekindsDNSMadeEasy'sAnycast+networkservesDNStrafficacrosshundredsofnameservers,allowingthenetworktomanageexponentiallymorerequeststhananin-housenetwork(alsoknownasaUnicastnetwork,becauseitonlyhostsDNSfromonelocation).
TherearemanydifferentwaystopreventDDoSattacks,butsomeofthesemethodscanbeverycostlyandnotpracticalforsmallbusinesses.
Someenterpriseorganizationsusein-houseDNSinfrastructures(unicastnetworks),howeverthesecancostthousandstosetup,andevenmoretomaintain.
Nottomention,expensivefirewallstoprotecttheseservers.
WanttolearnmoreaboutthebenefitsofusinganIPAnycast+networkOurexpertswroteawholewhitepaperonit!
Readithereforfree.
Page17DNSforNewbiesofthesein-houseDNSusersdon'trealizeisnomatterhowlargethefirewallis,iftheirincomingconnectionsintotheirnetworkaren'tlargeenough,thenit'sgameover.
Backtoourhighwayanalogy,iftheydon'tincreasethenumberoflanesintheirhighway,itdoesn'tmatterhowmanyshieldstheyhaveuptofendoffattackers.
Theattackwillactuallybreakthesystembeforethepacketsevenreachthefirewalls.
Eveniftheattackdoesreachthefirewalls,DDoSattackersarenotoriousforbypassingthem,becausetheyaresendingtinypacketsthatdon'tnormallyraiseredflagsformostsecuritysystems.
WhatmostOurexpertshaveactuallydevelopedamuchlargerlistofwaystoprepare,basedoffofyearsoffightingDDoSattacksthatwe'vemitigatedonaweekly(sometimesdaily)basis.
Seewhatourengineershavetosayaboutprotectingyourdomainsfromin-houseimplementationstoevenoutsourcingallofyournetworkingneedstoacloud-friendlyDNSprovider.
Youcanreadmorehere.
Page18DNSforNewbiesWhyOutsourceCHAPTER7havecoveredallthebasics,howcanyoustarttotakecontrolofyourownDNSThereamanydifferentmethodsouttherethathavehelpedpeoplefromhomeuserstolargeenterprises.
We'vealreadydiscussedafewwayssuchasbundlingyourDNShostingwithyourwebhost,orimplementinganin-houseDNSinfrastructure.
Whiletheseoptionsmaypromisefastspeedsorahands-offapproach(preconfiguredservicesandminimalcustomizability)toDNSservices,you'relackingsomeprettybasicfeaturessuchasFailoverandGlobalTrafficDirector.
TheseservicescomestandardwithoutsourcedDNSprovidersandallowyousetupfailsafesintheeventthatyoursitegoesdown.
Sothenwhat'saDNSproviderIt'sreallysimpleactually,DNSprovidersonlyofferDNShostingandmanagementservices.
Theirinfrastructuresaredesignedbyindustryexperts,builtforthecloud,andengineeredforthelowestresolutiontimesand100%reliability.
ThebestpartYoucantakeadvantageofaDNSprovider'sglobalnetworkwithouthavingtopayforalltheinfrastructureandmaintenancecostsofhavingdozensofworldwidefacilities.
NowthatwePage20DNSforNewbiesWhatisFailoverCHAPTER8youstartthenIfyou'vemadethedecisiontoletamanagedDNSproviderhandleyourquerytraffic.
.
.
thenyoustillneedtomakeafewmoredecisions.
Providersofferalotofdifferentfeaturesandservicesthatcanhelpwitheverythingfromsettingupyourcloud-basedDNSinfrastructure,tobackupplansincasesomethinggoeswrong.
Manyproviderswilltrytobundleoroversellyouwithproductsyoudon'tneed.
That'swhyyouneedtolearnwhateachofthesefeaturesdo,sothatyoucanmakedecisionspersonalizedforyou,basedonyourneeds.
WhenyoustartoutmanagingyourownDNS,thefirstthingyou'llprobablysetupisDNSFailover.
It'ssimpletosetupandyoucankeepyoursiteonlineeveniftheworsthappens.
WheredoRememberthoseDDoSattacksweweretalkingaboutearlierSayyoursitegetshitbyanattackwhichknocksyoursiteoffline.
Ifyouhadfailoversetup,yourcustomerswouldstillabletoviewyoursite.
Amazingright,buthowdoesitworkSimplysetupaback-upIPaddressforyoursitetofailoverto.
Wheneveryourprovidernoticesthatyoursiteisdown(FailoverMonitoring)itwillfirstchecktomakesureyourbackupIPisupandrunning.
ThenitwillautomaticallyredirectyourtraffictoyourbackupIPinstantly.
ItcanevenFailbackyourtrafficbacktoyouroriginalIPonceyoursiteisbackonline.
Page22DNSforNewbiesYourBackupPlanCHAPTER9alotofdifferentwaysyoucan"backup"yourdomainsoyoucanalwaysstayonline.
InadditiontoFailover,youcansetupSecondaryDNSwhichbasicallycreatesabodydoubleforyourdomain.
Thisisgreatforpeoplewhodecidetostickwithanin-houseinfrastructure,becausenowyoucanhostyourownDNS;butintheeventofanoutage,you'llhaveabackupversionofyoursiteonyourSecondaryDNSprovider'sservers.
It'sreallyeasy,allyouhavetodoistellyournameserverstoredirecttoyoursecondaryproviderintheeventofanoutage.
ThereareButwaitthere'smore.
.
.
youcanactuallycombineafewfeaturestogethertogetexponentiallymorelayersofredundancyandfailsafes.
YoucancombineFailoverwiththeGlobalTrafficDirector(GTD),whichoptimizesyourtrafficflowbasedonregionallocation.
Basically,intheeventofanoutage,yoursitewouldfailovertoyourbackupIP.
ButwhatifonlyoneregionissufferinganoutageUsingGTD,youcanspecifyallotherregionstoredirectaroundtheproblemareas.
Whenusedcorrectly,youcanslashresolutiontimesbyrespondingtoquerieswithinthesameregion.
ThatmeansifyouhaveaqueryingclientinLondon,theclientwillberespondedtobyaEuropeanserver.
Localresponsesmeanlesstraveltime,whichmeansfasterresolution,andpotentiallygreaterROI!
Page24DNSforNewbiesEveryoneneedsDNSCHAPTER10toadvertising,DNSrunseverything!
IfyourbusinessororganizationisdependentontheInternetforyoureCommercewebsite,communication,oradvertising.
.
.
ThenyouaredependentontheDomainNameSystem.
Sohowdoyouuseathird-partyprovidertooptimizeyourDNSperformanceWehavealreadycoveredafewofthebasicservicesthatprovidersoffer,buthowdotheseapplytoyourspecificorganization'sneedsTomakeyourjobeasier,wedevelopedatriedatruestrategyforeachofthetop6industriesthatneedDNSmanagement.
EcommercePage26DNSforNewbiesGetYourDNSStrategyAboutUsCHAPTER11DNSMadeEasyhasbeentheworldleaderinprovidingtoptierDNSservices.
DNSMadeEasyimplementedtheindustry'sfirsttripleindependentAnycastcloudarchitectureformaximumDNSspeedandDNSredundancy.
Overthepast14years,DNSMadeEasy'sserviceshavegrowntomanagehundredsofthousandsofcustomerdomainsreceivingmorethan30billionqueriesperday.
Today,DNSMadeEasybuildsonaproudhistoryof99.
9999%uptimeandisthepreferredDNShostingchoiceformostmajorbrands.
IfyouwanttolearnmoreabouthowDNSworksandthebenefitsofDNSmanagement,followourblog!
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comSince2002Page28DNSforNewbies