IP Multimedia Subsystems Overview - My Training on IMS


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IP Multimedia Subsystems Overview - My Training on IMS

  1. 1. IP Multimedia SubsystemPresenter : InamUllah KhosaHead of Product Development, Turnotech PakistanCornet Research Lab , Muhammad Ali Jinnah University
  2. 2. Presentation Plan  Background - Evolution of 2G, 2.5G and 3G  What is IMS  Standardization Bodies  Functions of IMS  IMS Architecture – The Big Picture  IMS Components and Interfaces  IMS Services Control Model  IMS Protocols  Conclusion
  3. 3. Setting the Stage. Revisiting the Past ! (Network Evolution)
  4. 4. 2G Digital Network Initially was merely designed for voice communication Logically divided into Access Network and Core Network Access Network is composed number of BTS and BSCs Core Network composed of MSC , GMSC , EIR, HLR, VLR,AUC Latter 2.5 Enhancements added PS Domain for Packet Data Support The PS Domain was composed of SGSN and GGSN GPRS Services support data rate of 56Kbps to 114Kbs
  5. 5. Background ( 2G)
  6. 6. 2.5 G
  7. 7. 3rd Generation Networks W-CDMA (UMTS) HSPA  HSDPA  HSUPA  HSPA+ UMTS-TDD  TD-CDMA  TD-SCDMA FOMA Super-Charged Offer users a wider range of more advanced services WAN voice telephony, video calls, and broadband wireless data
  8. 8. 3 & 3.5 G
  9. 9. 4G 3GPP LTE  improving spectral efficiency  lowering costs  improving services  LTE air interface is a completely new system based on  OFDMA in the downlink  SC-FDMA (DFTS-FDMA) in the uplink Flash-OFDM  adaptation to severe channel conditions  Robust against narrow-band co-channel interference  High spectral efficiency  Low sensitivity to time synchronization errors
  10. 10. The Birth of IMS (the New Kid)
  11. 11. New Kid –IMS Block Perspective
  12. 12. What is IMS ? IP Multimedia Subsystem Architectural Framework Overlay Network (PS and CS Networks)  Support for IP-Based Interactive Multimedia (QoS)  Mandatory Support for IPV6  Signaling based on IETF Protocol SIP , DIAMETER and COPS  Core and Access  Integration with PSTN Access Independent  Wireless ( UMTS , WLAN, WiMAX)  Wired ( DSL)
  13. 13. Overlay Network to PS and CS
  14. 14. IMS Standardization Worldwide Interoperability 3rd Generation Party Project (3GPP)  Groups of Telecommunications Associations  ITU , ETSI, ARIB/TTC, China Communications Standards Association, Alliance for Telecommunications Industry Solutions(North-America), Telecommunications Technology Association (South Korea)  Internet Engineering Task Force (IETF)  Technical Specifications TSpecs.  3GPP Releases
  15. 15. 3GPP and 3GPP2 3GPP standardization is based on IMT-2000 which uses W-CDMA as air interface 3GPP2 standardization is based on IS-95 which uses CDMA2000 as air interface
  16. 16. High Level Requirements Provisioning for the QoS Negotiation at the start of session and during End to End Quality of Service for Voice Sessions Roaming  Inter-operator QoS negotiations  Services provided by Home Network and Visiting Network Mandatory default set of media types to ensure interop ( audio:AMR, video: H.263) Access independence (GPRS, fixed, LAN) Support for session-oriented non-3GPP Internet apps
  17. 17. Can’t we Live without it ? Surely We Can But what about the Operators and Service Providers? Involved parties  Operators, Users, Content Providers, Legal Authorities, … All-IP network  Interactive Multimedia  QoS guarantee  Access transparency, seamless handover  AAA  Billing, Charging
  18. 18. Continued… Services and Service Aggregation  3rd party Application Servers  Services: No preferential treatment of voice  Voice (VoIP) is just one service, positioned at same level like  any other services Communication security in IP networks  Signaling and Media  Access and Core  Regulatory requirements (lawful interception)
  19. 19. Key Functions of IMS network Session Control/Management Subscription/Registrations Management Service Control Charging and Billing Operations, Administration, Maintenance and Provisioning (OAM&P/OSS) Interworking with PSTN
  20. 20. IMS Components Call State Control Functions  P-CSCF, I-CSCF and S-CSCF Home Subscriber Server(HSS) Media Resource Functions  MRFC, MRFP Interworking Functions  BGCF, MGCF, IMS-MGW, WAG/PDG, IMS-IWF, IETF-3GPP IWG Charging Functions  Online Charging System ( OCS)  Offline Charging System ( CCF/CDF) OAM&P Entities
  21. 21. The Big Picture !
  22. 22. IMS Protocols Interfaces
  23. 23. IMS Service Control Value Added Services are Provided by AS in IMS Application Servers are defined as a part of Service Profile Service Profiles are defined as a Part of User Profile Each Service Profile contains Initial Filter Criteria Initial Filter Criterion defines a user’s subscribed service
  24. 24. Sample Initial Filter CriteriaMethod =”INVITE” Session Case =”2”<? Xml version=”1.0” encoding=”UTF-8”?><IMSSubscription><PrivateID>sip:inam@mediaroutes.com </PrivateID><ServiceProfile> <PublicIdentity> <Identity>sip:inam@advcomm.net</Identity> </PublicIdentity> <PublicIdentity> <Identity>tel: +923335251992</Identity></PublicIdentity> <InitialFilterCriteria> <TriggerPoint> <SPT> <ConditionNegated>0</ConditionNegated> <Method>INVITE</Method> <Group>0</Group> </SPT> <SPT> <ConditionNegated>0</ConditionNegated> <SessionCase>2</SessionCase> <Group>0</Group> </SPT> </TriggerPoint> </InitialFilterCriteria> <ApplicationServer> <ServerName>sip:server@mediaroutes.com </ServerName> <DefaultHandling>1</DefaultHandling> </ApplicationServer></ServiceProfile></IMSSubscription>
  25. 25. Initial Filter Criteria Continued…. Each iFC contains Priority, Trigger Point and Application Server, Default Handling and These iFCs are evaluated on the initial requests  INVITE ,MESSAGE , OPTIONS, SUBSCRIBE S-CSCF checks filter criteria Once the AS has been identified S-CSCF creates Route header to forward message to AS Additionally, the S-CSCF places itself to the Route header to get back the message afterwards In the user part of the SIP URI of this own Route entry the S-CSCF may enter some state information to understand, that it already received and processed this message (other ways of providing state are possible)
  26. 26. Continued.. On registration the S-CSCF receives user profile from HSS Filter criteria determine the services that are applicable to the collection of Public User Identities of the profile S-CSCF assesses the criteria in the order of their priority Filter criteria contain trigger points, which are Boolean conditions If the trigger point fires the request goes to the corresponding AS After receiving back the request the next criteria is checked
  27. 27. Protocols Used in IMS Networks Session Initiation Protocol (SIP)  Registration , Authentication  Call Control/Session Establishment  Interworking Functions DIAMETER  Next Generation AAA Model  Pull/Push Registrations Data  User Profiles  Service Provisioning/Service Control  IMS Charging Common Open Policy Service ( COPS)  QoS Parameters Negotiations
  28. 28. User Identification in IMS Public User Identities ( IMPU)  IMS user has one or more Public User Identity  Either a SIP URI or a TEL URI  sip:+92-1111111@ufone.net;user=phone  tel:+92-42-664-832356  TEL URIs are required to make calls between IMS/PSTN - Envision: at least one TEL URI and one SIP URI Per Subscriber
  29. 29. Private User Identity Private User Identities(IMPI)  IMS user has one Private User Identity  Have the format of a Network Access Identifier (NAI, RFC 2486)  inam@mobilink.com  Not used for routing SIP messages  Used only for subscription identification and authentication  Similar function for IMS as the IMSI  (International Mobile Subscriber Identification) for GSM  Stored on UICC
  30. 30. Home Network Domain Home Network Domain  SIP URI that contains the home network domain name  Used to find the address of the home network during  registration procedure  Only one home network domain
  31. 31. Playgrounds for IMS IMSZONE ( http:imszone.org)  Diameter Stack  Home Subscriber Server (Cx,Sh)  Online Charging System  Offline Charging System  Media Server ( MRFC & MRFP)  OAM&P Manager and OAM&P Agent OpenIMSCore – http://openimscore.org  FHoSS: Home Subscriber Server  SERIMS: P-CSCF,I-CSCF, and S-CSCF  OpenIMS Lite: IMS Client
  32. 32. End of this Episode Thank You !