SIP URI scheme - Wikipedia

The SIP URI scheme is a Uniform Resource Identifier (URI) scheme for the Session Initiation Protocol (SIP) multimedia communications protocol. SIPURIscheme FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Addressingformat TheSIPURIschemeisaUniformResourceIdentifier(URI)schemefortheSessionInitiationProtocol(SIP)multimediacommunicationsprotocol.ASIPaddressisaURIthataddressesaspecifictelephoneextensiononavoiceoverIPsystem.SuchanumbercouldbeaprivatebranchexchangeoranE.164telephonenumberdialledthroughaspecificgateway.TheschemewasdefinedinRFC 3261. Contents 1Operation 2Spamandsecurityissues 3SIPSURIscheme 4Seealso 5References Operation[edit] ASIPaddressiswritteninuser@domain.tldformatinasimilarfashiontoanemailaddress.Anaddresslike: sip:[email protected] instructsaSIPclienttousetheNAPTRandSRVschemestolookuptheSIPserverassociatedwiththeDNSnamevoip-provider.example.netandconnecttothatserver.Ifthoserecordsarenotfound,butthenameisassociatedwithanIPaddress,theclientwilldirectlycontacttheSIPserveratthatIPaddressonport5060,bydefaultusingtheUDPtransportprotocol.[1]Itwillasktheserver(whichmaybeagateway)tobeconnectedtothedestinationuserat1-999-123-4567.ThegatewaymayrequiretheuserREGISTERusingSIPbeforeplacingthiscall.IfadestinationportisprovidedaspartoftheSIPURI,theNAPTR/SRVlookupsarenotused;rather,theclientdirectlyconnectstothespecifiedhostandport. AsaSIPaddressistext,muchlikeane-mailaddress,itmaycontainnon-numericcharacters.AstheclientmaybeaSIPphoneorotherdevicewithjustanumeric,telephone-likekeypad,variousschemesexisttoassociateanentirelynumericidentifiertoapubliclyreachableSIPaddress.TheseincludetheiNumInitiative(whichissuesE.164-formattednumbers,wherethecorrespondingSIPaddressisthenumber'@sip.inum.net'),SIPBroker-styleservices(whichassociateanumeric*prefixtotheSIPdomainname)andthee164.organde164.arpadomainnameservers(whichconvertnumberstoaddressesone-by-oneasDNSreverse-lookups). SIPaddressesmaybeuseddirectlyinconfigurationfiles(forinstance,inAsterisk(PBX)installations)orspecifiedthroughthewebinterfaceofavoice-over-IPgatewayprovider(usuallyasacallforwardingdestinationoranaddressbookentry).Systemswhichallowspeeddialfromauser'saddressbookusingaverticalservicecodemayallowashortnumericcode(like*75xx)tobetranslatedtoapre-storedalphanumericSIPaddress. Spamandsecurityissues[edit] Intheory,theownerofaSIP-capabletelephonehandsetcouldpublishaSIPaddressfromwhichtheycouldbefreelyanddirectlyreachedworldwide,inmuchthesamewaythatSMTPe-mailrecipientsmaybecontactedfromanywhereatalmostnocosttothemessagesender.Anyonewithabroadbandconnectioncouldinstallasoftphone(suchasEkiga)andcallanyoftheseSIPaddressesforfree. Inpractice,variousformsofnetworkabusearediscouragingcreationandpublicationofopenlyreachableSIPaddresses: Thespam(electronic)whichhasrenderedSMTPthe"spammailtransportprotocol"couldpotentiallymakepublishedsip:numbersunusableasthenumbersarefloodedwithVoIPspam,usuallyautomaticannouncementdevicesdeliveringpre-recordedadvertisements.Unlikemailto:,sip:establishesavoicecallwhichinterruptsthehumanrecipientinrealtimewitharingingtelephone. SIPisvulnerabletoCallerIDspoofingasthedisplayednameandnumber,muchlikethereturnaddressone-mail,issuppliedbythesenderandnotauthenticated. Serverssupportinginboundsip:connectionsareroutinelytargetedwithunauthorisedREGISTERattemptswithrandomnumericusernamesandpasswords,abruteforceattackintendedtoimpersonateindividualoff-premisesextensionsonthelocalPBX Serverssupportinginboundsip:connectionsarealsotargetedwithunsolicitedattemptstoreachoutsidenumbers,usuallypremium-ratedestinationssuchascaller-pays-airtimemobileexchangesinforeigncountries. Intheserverlogs,thislookslike: [Oct2315:04:02]NOTICE[4539]:chan_sip.c:21614handle_request_invite:Callfrom''toextension'011972599950423'rejectedbecauseextensionnotfoundincontext'default'. [Oct2315:04:04]NOTICE[4539]:chan_sip.c:21614handle_request_invite:Callfrom''toextension'9011972599950423'rejectedbecauseextensionnotfoundincontext'default'. [Oct2315:04:07]NOTICE[4539]:chan_sip.c:21614handle_request_invite:Callfrom''toextension'7011972599950423'rejectedbecauseextensionnotfoundincontext'default'. [Oct2315:04:08]NOTICE[4539]:chan_sip.c:21614handle_request_invite:Callfrom''toextension'972599950423'rejectedbecauseextensionnotfoundincontext'default'. anattempttocallaPalestinianmobiletelephone(Israel,countrycode+972)byrandomlytrying9-(acommoncodeforanoutsidelinefromanofficePBX),011-(theoverseascallprefixintheNorthAmericanNumberingPlan)and7-(ontheoff-chanceaPBXisusingitinsteadof9-foranoutsideline).Securitytoolssuchasfirewallsorfail2banmustthereforebedeployedtopreventunauthorisedoutsidecallattempts;manyVoIPprovidersalsodisableoverseascallstoallbutcountriesspecificallyrequestedasenabledbythesubscriber. SIPSURIscheme[edit] TheSIPSURIschemeadherestothesyntaxoftheSIPURI,differingonlyinthattheschemeissipsratherthansip.ThedefaultInternetportaddressforSIPSis5061unlessexplicitlyspecifiedintheURI. SIPSallowsresourcestospecifythattheyshouldbereachedsecurely.ItmandatesthateachhopoverwhichtherequestisforwardeduptothetargetdomainmustbesecuredwithTLS.Thelasthopfromtheproxyofthetargetdomaintotheuseragenthastobesecuredaccordingtolocalpolicies. SIPSprotectsagainstattackerswhichtrytolistenonthesignalinglink.Itdoesnotproviderealend-to-endsecurity,sinceencryptionisonlyhop-by-hopandeverysingleintermediateproxyhastobetrusted. Seealso[edit] FederatedVoIPandtelephonenumbermapping e164.arpa SecurityDescriptionsforSDP Mikeykeyexchangemethod ZRTPend-to-endkeyexchangeproposal References[edit] ^SessionInitiationProtocol(SIP):LocatingSIPServers.doi:10.17487/RFC3263.RFC3263. vteUniformResourceIdentifier(URI)schemesOfficial about acct crid data file ftp geo gopher http https info ldap mailto nfs nntp sip/sips tag telnet urn view-source ws/wss xmpp Unofficial coffee ed2k gemini feed finger irc/irc6/ircs ldaps magnet rsync ymsgr Protocollist Retrievedfrom"https://en.wikipedia.org/w/index.php?title=SIP_URI_scheme&oldid=1062792969" Categories:URIschemesInternetprotocolsHiddencategories:ArticleswithshortdescriptionShortdescriptionmatchesWikidata Navigationmenu Personaltools NotloggedinTalkContributionsCreateaccountLogin Namespaces ArticleTalk English Views ReadEditViewhistory More Search Navigation MainpageContentsCurrenteventsRandomarticleAboutWikipediaContactusDonate Contribute HelpLearntoeditCommunityportalRecentchangesUploadfile Tools WhatlinkshereRelatedchangesUploadfileSpecialpagesPermanentlinkPageinformationCitethispageWikidataitem Print/export DownloadasPDFPrintableversion Languages Addlinks