b@>;tag=4992881234
Call-ID:
898234234@
CSeq:
1993402NOTIFY
Max-Forwards:
70
Event:
refer
Subscription-State:
active;expires=(dependsonRefer-ToURI)
Contact:
sip:
b@
Content-Type:
message/sipfrag;version=2.0普通呼叫的type为:
application/sdp
Content-Length:
20
2.Replace的使用
过程如下图所示:
3.EarlyMediaApplications
在SIP的EarlyMedia中使用的是183信令来实现,如下图:
4.SIP自动callback的应用
5.用InstantMessagetoTransferaCall
6.SIPMessageWaiting
7.SIPCallControlinConferencing
三、新功能
1.SigComp
theSignalingCompression(SigComp)add-onmoduleisasolutionforcompressingSIP
signaling.SinceSIPmessagesaretextbased,theyarenotoptimizedintermsofsize.Forexample,
typicalSIPmessagesrangefromafewhundredbytestotwothousandbytesormore(RFC3261).
Withtheplannedusageoftheseprotocolsinwirelessandcellularhandsets,andaspartofthe3GPP
(ThirdGenerationPartnershipProject)requirementsforIMS(IPMultimediaSubsystem),thelarge
messagesizeisproblematicandmessagecompressionismandatory.
2.DLA(DynamicLocalAddress)
enablesthedynamicopeningandclosingofthelocalIP
addresses,whichareusedforrequestsendingandreception,atanymomentoftheSIPStacklife
cycle.Thisfeatureistypicallyusedwithmultihomedhost.DLAisusedforbroadband(DSL,cable),
aswellaswirelessandcellularnetworks,tosupporthandoffsandIPaddresschangesbyservice
providers.
3.IP_TOS
determinesthevalueoftheTypeofServicefieldintheIPheaderofallpacketsthatare
sentovertheoutgoingconnections.(SupportedforIPv4addressesonly.)
4.TransmitterObject
theSIPStackusestransmitterobjectsformessagesending.Eachtransaction
objectholdsasingletransmitterobjectandusesittosendSIPmessagesandmessage
retransmissions.Theapplicationcanusethisnewobjectforsendinganout-of-scoperequestor
responsewithoutusingtheTransactionlayer.
5.REFERRFC3515
REFERisaSIPmethoddefinedbyRFC3515(SessionInitiationProtocol
ReferMethod).TheREFERmethodindicatesthattherecipientoftheREFERrequestshouldcontact
athirdpartyusingthecontactinformationprovidedintheREFERrequest.RFC3515providesa
mechanismallowingthepartythatissendingtheREFERtobenotifiedoftheoutcomeofthe
referencedrequestwithaNOTIFYrequest.Thisimplementationusessubscriptionobjectsfor
REFERimplementation.ItreplacesthepreviousREFERimplementationandisintroduceddueto
standardmodifications.
6.Client-sideforking
inpreviousSIPToolkitversions,ifarequestwasforked,theSIPStackonthe
clientsideautomaticallyconnectedthefirstestablisheddialog,anddidnotallowtheapplicationto
chooseadifferentdialogorconnectmultipledialogs.Inthecurrentversion,theCall-legand
Subscriptionmoduleswereenhancedtoallowthisflexibility.
7.Mergingdisabling
ifaproxyforksarequestandeventuallythetworequestsareterminatedatthesameUserAgentServer(UAS),theUASneedstomergethemintoonerequest.TherearecaseswheretheUASisagatewayandthereforewillwanttoavoidthemessagemerging.Thisflexibilityiscurrentlyavailable.
8.TransportLayerenhancements
twofunctionalitieswereadded.Anapplicationcannowblockincomingconnectionsevenbeforedatawasreceivedonthem.Thisletstheapplicationimplementawhite/blackIPaddresslistandhandlethedenialofserviceattacksinabetterway.Accesstotheincomingrawbuffersothattheapplicationcandumpbuffertofileordiscardthebuffer,forexample.
9.A-synchronousDNS
DNSfunctionalitywasenhancedandisnowa-synchronous,improvingperformanceespeciallyformulti-sessionapplicationssuchasgatewaysandservers.
10.DNSserverruntimeconfiguration
insomecases,itisrequiredtochangetheDNSserverthatisbeingusedatruntime.ThisisnowpossibleviatheSIPToolkitAPIs.
11.ManualPRACK
theapplicationcannowcontrolthesendingofPRACK/200.Thisisanadditiontotheautomaticfunctionalityavailableinpreviousversions.
12.Primitivescompilationflag
thisnewcompilationflagreplacestheEXTRA_LEANcompilationflag.Itremovesthedialoglayer,allowingapplicationtoworkdirectlyabovetheTransactionlayer.Additionally,itremovesspecificsupportofcertainheaders.Theapplicationcanstillusetheseheadersbyaddingspecificsupportintheapplicationitself.
13.MiddleLayerforlow-levelservices
theRADVISIONoperatingsystemabstractionlayerwaswrappedandsomeofitsAPIsarenowexposedsotheapplicationcanuseservicessuchastimersandselect.
14.Viaheadercontrol
someimplementations,suchaswhenusingaSTUN/TURNserver,requiremanualmodificationoftheViaheaderafterDNSwascompleted.Thiscontrolandflexibilityisnowpossible.
15.Subscriptionhighavailability
theRADVISIONSIPStackprovidesastoreandrestoremechanismthatenablestheapplicationtobackupsubscriptionsintheACTIVEstate.Backingupsubscriptionsletsapplicationdevelopersimplementredundancycapabilitiesintheirsystems,allowingback-upsystemsto“takeover”whentheprimarysystemgoesdown.Whenstoringanactivesubscription,allofthesubscriptionparametersarecopiedintoaconsecutivebuffer.Theapplicationcanthensavethisbufferanduseitwhenrestoringthebackupobject.
16.Authenticationenhancement
theauthenticationmechanismenablesaUserAgentClient(UAC)toproveauthenticitytoserversorproxieswhichrequireauthentication.TheSIPStacksupportsSIPauthenticationusingtheHTTPDigestSchemeasdescribedinRFC3261andRFC2617.Inthecurrentversion,supportofthe“auth-int”qualityofprotection(qop)wasadded.Forserver-sideauthentication,only“auth”qopissupported.
17.RequirementsforEnd-to-MiddleSecurityfortheSessionInitiationProtocol(SIP)【rfc4189】
ASessionInitiationProtocol(SIP)UserAgent(UA)doesnotalways
trustallintermediariesinitsrequestpathtoinspectitsmessage
bodiesand/orheaderscontainedinitsmessage.TheUAmightwantto
protectthemessagebodiesand/orheadersfromintermediaries,except
thosethatprovideservicesbasedonitscontent.Thissituation
requiresamechanismcalled"end-to-middlesecurity"tosecurethe
informationpassedbetweentheUAandintermediaries,whichdoesnot
interferewithend-to-endsecurity.Thisdocumentdefinesasetof
requirementsforamechanismtoachieveend-to-middlesecurity
18.TheStreamControlTransmissionProtocol(SCTP)asaTransportfortheSessionInitiationProtocol(SIP)【rfc4168】
ThisdocumentspecifiesamechanismforusageofSCTP(theStream
ControlTransmissionProtocol)asthetransportmechanismbetweenSIP
(SessionInitiationProtocol)entities.SCTPisanewprotocolthat
providesseveralfeaturesthatmayprovebeneficialfortransport
betweenSIPentitiesthatexchangealargeamountofmessages,
includinggatewaysandproxies.AsSIPistransport-independent,
supportofSCTPisarelativelystraightforwardprocess,nearly
identicaltosupportforTCP
19.SessionInitiationProtocol(SIP)-H.323