application-layer mobility using sip henning schulzrinne, elin wedlund mobile computing and...
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Application-Layer Mobility UsiApplication-Layer Mobility Using SIPng SIPHenning Schulzrinne, Elin WedlundHenning Schulzrinne, Elin WedlundMobile Computing and Communications Review, Volume 4, NumbeMobile Computing and Communications Review, Volume 4, Number 3r 3
Presenter: Presenter: 許啟裕許啟裕
Date: 2005/5/10Date: 2005/5/10
OutlineOutline
Introduction to SIPIntroduction to SIP Classification of MobilityClassification of Mobility Network Layer MobilityNetwork Layer Mobility Application Layer (SIP-based) Application Layer (SIP-based)
MobilityMobility ConclusionConclusion
Introduction to SIP Introduction to SIP (1/9)(1/9) A A powerful alternativepowerful alternative to H.323 to H.323 More More flexibleflexible, , simplersimpler Easier to implement advanced Easier to implement advanced
featuresfeatures Better to support of intelligent user Better to support of intelligent user
devicesdevices Transport independenceTransport independence (UDP, (UDP,
TCP, or SCTP)TCP, or SCTP)
Introduction to SIP Introduction to SIP (2/9)(2/9) Developed in SIP working Group Developed in SIP working Group
in IETFin IETF– Work Work began 1995began 1995– Sep. 1999 splitSep. 1999 split from from MMUSICMMUSIC
MMultiparty ultiparty MuMultimedia ltimedia SSessessiion on CControlontrol
– Proposed standard Proposed standard RFC 2543RFC 2543, , February 1999February 1999
– New version of SIP – RFC 3261, New version of SIP – RFC 3261, June June 20022002
Introduction to SIP Introduction to SIP (3/9)(3/9) SIP is an SIP is an application-layerapplication-layer signalingsignaling
protocolprotocol HTTP-likeHTTP-like, “request-response”, “request-response”
– EstablishEstablish, , modifymodify, and , and terminateterminate multi multimedia sessions.media sessions.
SIP+SIP+(Session Description Protocol)(Session Description Protocol)SSDPDP
Introduction to SIP Introduction to SIP (4/9)(4/9) SeparateSeparate signalingsignaling and and mediamedia streams streams
Introduction to SIP Introduction to SIP (5/9)(5/9) SIP addressing and namingSIP addressing and naming
– The entities The entities addressed addressed by SIP are by SIP are users at hostusers at hostss (SIP (SIP URIURI: : UUniform niform rresource esource iidentifier)dentifier)
– Email-likeEmail-like identifier of the form user@host identifier of the form user@host UserUser: : user nameuser name or or telephone numbertelephone number HostHost: : domain namedomain name or or numeric network numbernumeric network number
– For example,For example, [email protected]@npust.edu.tw 09441688880944168888@@npust.edu.twnpust.edu.tw Charles@[email protected]
Introduction to SIP Introduction to SIP (6/9)(6/9) SIP defines a number of logical SIP defines a number of logical
entities, namelyentities, namely– User agentsUser agents– Redirect serversRedirect servers– Proxy serversProxy servers– RegistrarsRegistrars
Introduction to SIP Introduction to SIP (7/9)(7/9) User agentUser agent
– User AgentUser Agent Client Client - - InitiateInitiate SIP SIP requestrequest– User AgentUser Agent Server Server - - AcceptsAccepts or or rejectsrejects call call
Introduction to SIP Introduction to SIP (8/9)(8/9) Redirect ServerRedirect Server
– Redirect server Redirect server usesuses a a database or database or location servicelocation service to to look up a userlook up a user
Introduction to SIP Introduction to SIP (9/9)(9/9) Proxy ServerProxy Server
– Handle requestsHandle requests or or forwardforward requests to other s requests to other serverservers
– Can be used for call forwarding, time-of-day reCan be used for call forwarding, time-of-day reouting, or follow-me servicesouting, or follow-me services
Classification of Classification of MobilityMobilityLayersLayers
RangeRangeApplication Application Layer Layer
Transport Transport Layer Layer
Network Network LayerLayer
MacromobilitMacromobilityy
SIP SIP TCP-TCP-Migrate Migrate
MIP MIP
MicromobilitMicromobilityy
HMSIP HMSIP HAWAIIHAWAII
CIPCIP
IDMPIDMP
TIMIP TIMIP
Network Layer MobilityNetwork Layer Mobility
AdvantageAdvantage– RetainRetain home home IP addressIP address while while changing changing
attachment pointattachment point of the network of the network– Keep tracking Keep tracking host locationhost location
DisadvantageDisadvantage– Difficult to deployDifficult to deploy, ISP has to provide home , ISP has to provide home
agentagent– Need to Need to modify convention IP stackmodify convention IP stack– Add Add 8-20 bytes overhead8-20 bytes overhead each packet each packet– Cannot supportCannot support session, service and session, service and
personal mobilitypersonal mobility
Application Layer (SIP-Application Layer (SIP-based) Mobility (1/16)based) Mobility (1/16) AdvantageAdvantage
– Ease to deployEase to deploy– SupportSupport session, service, personal, and session, service, personal, and
terminal mobilityterminal mobility– Network transparentNetwork transparent
DisadvantageDisadvantage– A A large amountlarge amount of of signaling overheadsignaling overhead– RTPRTP does does notnot support support QoSQoS
Application Layer (SIP-Application Layer (SIP-based) Mobility (2/16)based) Mobility (2/16) In this paper, In this paper, four types mobilityfour types mobility
have been defined.have been defined.– TerminalTerminal Mobility Mobility– SessionSession Mobility Mobility– ServiceService Mobility Mobility– PersonalPersonal Mobility Mobility
Application Layer (SIP-Application Layer (SIP-based) Mobility (3/16)based) Mobility (3/16) Terminal MobilityTerminal Mobility
– Terminal Terminal altersalters the the attachment pointattachment point of of the network.the network.
– Two scenarios have to been concernedTwo scenarios have to been concerned Pre-callPre-call: Mobile host (MH) : Mobile host (MH) acquiresacquires a a newnew
addressaddress prior to receivingprior to receiving or or makingmaking a a callcall Mid-callMid-call: : MHMH is movingis moving and and sending sending
another another INVITE requestINVITE request to the to the correspondent host (CH)correspondent host (CH)
Application Layer (SIP-Application Layer (SIP-based) Mobility (4/16)based) Mobility (4/16) Pre-callPre-call
Application Layer (SIP-Application Layer (SIP-based) Mobility (5/17)based) Mobility (5/17) Pre-call MobilityPre-call Mobility
– The MH The MH simply re-registerssimply re-registers with its home with its home registrar each time it obtains a new IP registrar each time it obtains a new IP addressaddress
A A large amountlarge amount of the of the register signaling overheadregister signaling overhead WasteWaste of the of the network bandwidthnetwork bandwidth
– The only The only difficult partdifficult part there is the ability there is the ability to to detectdetect, at the , at the application layerapplication layer, when , when IPIP has has changedchanged..
The client simplyThe client simply polls polls the the OSOS every few seconds every few seconds Power consumptionPower consumption
Application Layer (SIP-Application Layer (SIP-based) Mobility (6/16)based) Mobility (6/16) PagingPaging, for , for MH power conservationMH power conservation, ,
can also be implemented in SIPcan also be implemented in SIP This work assumes that This work assumes that proxiesproxies are are
organized hierarchicallyorganized hierarchically E.g.E.g.
– With a proxy for each wireless network, With a proxy for each wireless network, region, cell cluster and base stationregion, cell cluster and base station
Application Layer (SIP-Application Layer (SIP-based) Mobility (7/16)based) Mobility (7/16) Mid-callMid-call
Application Layer (SIP-Application Layer (SIP-based) Mobility (8/16)based) Mobility (8/16) The The location updatelocation update takes takes one one-wayone one-way
delaydelay after the application in the MH after the application in the MH recognizes that it has acquired a new IP recognizes that it has acquired a new IP addressaddress
For For wideband accesswideband access, the , the delay is delay is probably equalprobably equal to to propagation delaypropagation delay plus a few millisecondsplus a few milliseconds
For For narrowband systemsnarrowband systems, it may impose , it may impose delays of several tens of millisecondsdelays of several tens of milliseconds
Application Layer (SIP-Application Layer (SIP-based) Mobility (9/16)based) Mobility (9/16) RTP translatorRTP translator interceptsintercepts the the
media packets and media packets and directsdirects them them toto the the current location of the MHcurrent location of the MH
Insertion of an RTP translator Insertion of an RTP translator reducesreduces handoff delayhandoff delay to the one- to the one-way between the MHway between the MH
Application Layer (SIP-Application Layer (SIP-based) Mobility (10/16)based) Mobility (10/16) Session MobilitySession Mobility It It allowsallows a a useuser to r to maintainmaintain a a media media
sessionsession even while changing terminals even while changing terminals For example,For example,
– A caller may want A caller may want continue a sessioncontinue a session begun on a begun on a mobile devicemobile device on the on the desktop desktop pcpc when when enterenter her her officeoffice
– A A user user may also want to may also want to move partsmove parts of a of a sessionsession, e.g., if he has specialized devices , e.g., if he has specialized devices for audio and video, such as a for audio and video, such as a video video projectorprojector, , video wallvideo wall or or speakerphonespeakerphone
Application Layer (SIP-Application Layer (SIP-based) Mobility (11/16)based) Mobility (11/16) Session mobility using SIP can be suSession mobility using SIP can be su
pported in at least three wayspported in at least three ways– In the simplest approach, In the simplest approach, using new INVusing new INV
ITE requestITE request..– One mechanism for such configuration One mechanism for such configuration
could be MGCP or could be MGCP or MegacoMegaco– Two better solutions, namely Two better solutions, namely third-partthird-part
y call controly call control or the or the REFER mechanismREFER mechanism
Application Layer (SIP-Application Layer (SIP-based) Mobility (12/16)based) Mobility (12/16) Third-party call controlThird-party call control
Application Layer (SIP-basApplication Layer (SIP-based) Mobility (13/16)ed) Mobility (13/16) REFER methodREFER method
Application Layer (SIP-basApplication Layer (SIP-based) Mobility (14/16)ed) Mobility (14/16) Personal MobilityPersonal Mobility It It allowsallows to to addressaddress a a single usersingle user
located located at different terminalsat different terminals by by the same logical addressthe same logical address
Both Both 1-to-n1-to-n (one address many (one address many potential terminal) and potential terminal) and m-to-1m-to-1 (many addresses reaching one (many addresses reaching one terminal) mapping are usefulterminal) mapping are useful
Application Layer (SIP-basApplication Layer (SIP-based) Mobility (15/16)ed) Mobility (15/16) Personal MobilityPersonal Mobility
Application Layer (SIP-basApplication Layer (SIP-based) Mobility (16/16)ed) Mobility (16/16) Service MobilityService Mobility It It allowsallows users to users to maintainmaintain accessaccess
to their to their servicesservices even while even while moving or changing devices and moving or changing devices and network service providersnetwork service providers
For instance, For instance, usersusers will likely will likely wantwant to to maintainmaintain include their include their speed speed dial listsdial lists, , address booksaddress books, and so , and so on on in Voice-over-IP environmentin Voice-over-IP environment..
ConclusionConclusion
Application-layer mobilityApplication-layer mobility can either can either partially replacepartially replace or or complement complement network-layer mobilitynetwork-layer mobility
SIP-based mobilitySIP-based mobility can be used to can be used to provide provide all all common common forms offorms of mobilitymobility, including , including terminalterminal, , personalpersonal, , serviceservice, and , and sessionsession mobilitymobility
Thank you for your Thank you for your attentionattention