Kỹ thuật IMS part 16

IMS – IP Multimedia Subsystem Introduction Evolution of architectures for telecom services Intelligence embedded in switches Switching system software PSTN, ISDN Intelligence in a separate service node IN SCP & CSE INAP, CAMEL Intelligence of cooperating components 3G, NGN, IMS SIP, OSA/PARLAY, JAIN Ewolution of service implementation model Traditional model closed Services and applications New model - open Services & applications + management API Call control and switching Multimedia session control API Physical transport Service interface Network interface Physical transport Opening of the control infrastructure and service architecture using standard APIs - Parlay OSA API i JAIN API Breaking of the classic value chain Separation of service development, deployment and operation VNO and MVNO models Private networks Fixed networks Mobile networks Change of model: „Spaghetti” -> „Lasagna” Application and content Common service capabilities Transport and access „spaghetti” type networks Vertical model „lasagna” type networks Horizontal model „Convergence”- a buzzword … Overloaded concept – many flavours of „convergence” Voice - data Common transport network FMC ETSI TISPAN NGN Terminal convergence GSM/UMTS + WLAN Session continuity Single address (ENUM) Application convergence Context and presence embedded in applicatiions Click-to-call Convergence – key factors Telecommunications – A mix of solutions, technical and legal aspects Presence and context Broadband access Mobility Wireless access Convergence Computer science and Internet – Content, media, networked IT services Web 2.0/3.0 Security and privacy Multimedia Open source + CopyLeft Areas of convergence Convergence planes Network Services and applications Terminals Charging Contents Everybody can (almost) offer everything … TV TV TV TV Mobile Mobile Mobile Mobile Fixed Fixed Fixed Fixed Internet Internet Internet Internet Market liberalization (LLU, BSA, ) + business models (MVNO/MVNE, networked IT services…) + resource sharing (fibers, lambdas, ducts, masts, servers, …) IP Multimedia (IM) Domain Implementation of multimedia services Integration of PS and CS domains and services IM Domain - IMS GSM BSS PS Domain Home Domain ME PDN (IP) Core network CS Domain UMTS RNS (UTRAN) PSTN 10 Parlay OSA application servers – third parties Service Delivery Platform (Application server) Parlay X App Parlay X App Parlay App Parlay App Parlay App HSS Parlay X GW Parlay API (MPCC, MMM, Presence, Charging Service Platform Trigger Points Sh = Diameter Cx = Diameter SIP Interface ISC S-CSCF SIP-Server SIP S SPT P T Diameter Inne sieci dostępowe Ro + Rf = Diameter Online &Offline Charging (ECF, CCF) Filter criteria Source: T Magedanz (TU Berlin / Fraunhofer FOKUS) 46 IMS components Visited network Home network Sh HSS AS Cx P-CSCF I-CSCF Mw S-CSCF ISC MRF Mi Gm BGCF UE MGCF Mj 47 Home Subscription Server (HSS) HSS (Home Subscriber Server) Technically, an evolution of the HLR Central repository for user-related information location information security information (authentication and authorization) user profile information (the services that the user is subscribed to) S-CSCF allocated to the user SLF (Subscriber Location Function) Simple database that maps users’ addresses to HSSs 48 HSS – Home Subscriber Server Sh SLF HSS AS Diameter MAP GPRS access Mw SIP ISC Dx Cx Cx SIP Diameter I-CSCF Mw S-CSCF SIP 49 The first registration Visited network UA Home network P-CSCF Register S-CSCF HSS I-CSCF Register UAR UAA Selection of r S-CSCF Register MAR Authentication vector selection 10 401 Unauthorised RAND||AUTN 11 Register RES 401 Unauthorised RAND||AUTN 12 Register RES MAA RAND||AUTN||XRES||CK||IK 401 Unauthorised RAND||AUTN UAR: User-Authorization-Request UAA: User-Authorization-Answer MAR: Multimedia-Authentication-Request MAA: Multimedia-Authentication-Answer SAR: Server-Assignment-Request SAA: Server-Assignment-Answer RAND: Random challenge AUTN: Network Authorization Token CK: Ciphering Key IK: Integrity Key 13 UAR 14 UAA 15 Register RES Authentication 18 SAR 19 SAA 22 OK 21 OK CK||IK 20 OK CK||IK 50 Example: registration Home Network of Mobile A Home network of Mobile B HSS - A HSS - B 5 I-CSCF - A S-CSCF - A S-CSCF - B I-CSCF - B P-CSCF - A P-CSCF - B Call Control Mobile A Mobile B Network Visited by Mobile A Network Visited by Mobile B 51 IMS users session SIP INVITE Retrieving user’s profile Retrieving user’s profile Execution of a service scenario Execution of a service scenario INVITE forwarding to User B Resolution of User B home network address and INVITE forwarding SDP session negotiation / Reservation of resources 10 Ringing / Alerting Identification of Registrar for user B and INVITE forwarding 11 Answer / call active Control Home network of calling user Bearer Home network of called user DNS HSS Diameter HSS Diameter AS SIP Diameter S-CSCF I-CSCF S-CSCF AS SIP SIP SIP Visited network of caller P-CSCF P-CSCF Visited network of callee 11 10 SIP UE Access Packet Core RTP Packet Core SIP UE Access 52 Example – mobile call Home Network of Mobile A HSS - A Home network of Mobile B HSS - B I-CSCF - A S-CSCF - A S-CSCF - B I-CSCF - B P-CSCF - A P-CSCF - B Call Control Mobile A Network Visited by Mobile A Network Visited by Mobile B Mobile B 53 IMS to PSTN call SIP INVITE ISUP IAM Retrieving user’s profile Ringing / Alerting Execution of a service scenario Selection of access to PSTN and selection of MGCF Answer / Connect Seizing of a link/trunk and determination of MGW capabilities Control SDP session negotiation / Reservation of resources Bearer Network wizyty by the caller Home network of the caller SIP Access P-CSCF MGCF SIP H.248 BGCF SIP RTP stream MGW PCM SIP Diameter ISUP Packet Core BGCF S-CSCF HSS SIP AS PSTN 54 Call to PSTN (CS domain) Home Network of Mobile A HSS - A User Profile BGCF - A PSTN MGCF - B User Profile I-CSCF - A S-CSCF - A Gateway Control Mobile A P-CSCF - A MGW - B Network Visited by Mobile A 55 IMS Session Setup and Control Happens after user registration (and authentication!) Why we need the IMS session setup? Capability negotiation (e.g codecs, port numbers, addresses) Network resource reservation and the support of QoS preconditions Additional functions performed by the IMS during the IMS Session Setup: Routing to the terminating IMS (= the IMS of the B-Party) Routing / Breakout to the PSTN / CS-Domain when the B-Party is not in the IMS, but in the PSTN / CS-Domain Service Control / Invocation of Application Servers to trigger the execution of Originating- and/or Terminating IMS Services Integrity/Confidentiality Protection of SIP Messages QoS/Media Authorization SIP Signaling Compression 56 IMS Session Setup and Control 1/4 Source: T Magedanz (TU Berlin / Fraunhofer FOKUS) 57 IMS Session Setup and Control 2/4 Source: T Magedanz (TU Berlin / Fraunhofer FOKUS) 58 IMS Session Setup and Control 3/4 Source: T Magedanz (TU Berlin / Fraunhofer FOKUS) 59 IMS Session Setup and Control 4/4 Source: IMS Tutorial -T Magedanz (TU Berlin / Fraunhofer FOKUS) 60