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- 1. DIT Dar es Salaam institute of Technology (DIT) ETU 08102 Digital Networks Ally, J jumannea@gmail.com
- 2. DIT IP Multimedia Subsystem (IMS) Basics
- 3. Voice and Video over IP DIT
- 4. Voice and Video over IP After some early resistance, telecom companies have embraced VoIP The VoIP standards war is over The winner: Session Initiation Protocol (SIP) What if? An architecture was designed to support services and multiple networks The media is not just voice, but multi-media SIP signaling used throughout DIT
- 5. What is IMS? IMS is an architecture, it is not a protocol. Open-systems architecture that supports a range of IP-based services over both Private and Carrier networks, employing both wireless and fixed access technologies. IMS is defined by 3GPP.
- 6. DIT IMS Basic Concept IMS is an architecture that solves the continuing demands and frustrations of users and enterprises. The ultimate goal of the architecture is to define a model that separates the services offered by fixed-line (traditional telecom), mobile (traditional cellular), and converged service providers (cable companies and others who provide triple-play — voice, video, and data services) from the access networks used to receive those services. For instance, a classic example would be the ability of a mobile cellular phone to switch to WiFi VoIP (mid-call) when it discovers a valid network to use. In this scenario, your mobile phone would dynamically move your existing call over the cellular network to a valid WiFi network (for example, your home wireless network) when you came into range, saving your cellular airtime and providing additional bandwidth for data communications. IMS, when fully deployed, will enable you to choose a Service Provider (SP) not by the quality or ubiquity of their network, but by the services they offer. The “network,” or how you connect to those services, will become irrelevant.
- 7. Access Network Other Networks Web PortalWeb PortalWeb PortalWeb Portal ApplicationApplication ServersServers ApplicationApplication ServersServers SessionSession ControlControl SessionSession ControlControl CentralizedCentralized DatabasesDatabases CentralizedCentralized DatabasesDatabases MediaMedia Control &Control & GatewaysGateways MediaMedia Control &Control & GatewaysGateways MediaMedia ServerServer MediaMedia ServerServer Access Layer Session Control Layer Application Layer Open Industry Standard Support for a Variety of Applications: • Speed Applications to market Common Session Control Element to Provide Service Interworking • Predictable interactions between multiple services Common Subscriber Database with Open Interfaces Service Consistency Across Wireless, Wireline and VoIP Endpoints: •Retain ownership of the subscriber and their services •Ability to provide differentiated services Distributed Session Control • IMS flexibility and scalability reduce OPEX • Support mobility/portability Common support for CoS, QoS, security, scalability, reliability, and performance Common OAM&P Environment • Ease integration into OSS/BSS/NMS CommonCommon OAM&P,Billing,OAM&P,Billing, etc.etc. CommonCommon OAM&P,Billing,OAM&P,Billing, etc.etc. Capable of Interworking with the PSTN (i.e. legacy IN- based services) IP Multimedia Subsystem (IMS) - Key Attributes
- 8. RNC MSC(Server) SGSN GGSN CNCN MGW BSC UMTS/GPRSUMTS/GPRS WLANWLAN CorporateCorporate P-CSCF I-CSCF MRF MGW MGCF IMSIMS S-CSCF SIPApplication ServersSIPApplication Servers HSS CDMA 2000CDMA 2000 DSL/Cable ModemDSL/Cable Modem DSLAM/CMTS IMS Access Network Independence
- 9. ClientsClientsDevicesDevicesAccessAccessTransportTransportSessionSession ControlControl ApplicationsApplications Managed Core IP Network Media GW Signaling GW MRFCMRFCMRFCMRFCCSCFCSCFCSCFCSCF Service BrokerService BrokerService BrokerService Broker HSSHSSHSSHSS Pres. Data Loc. Data Subs Data Micro BillingMicro Billing IntegratedIntegrated Pre-paid &Pre-paid & PostpaidPostpaid Micro BillingMicro Billing IntegratedIntegrated Pre-paid &Pre-paid & PostpaidPostpaid AAA Group Lists Media Server Media Server POTS phone GGSN PDSN MSC Cellular Access Point WiFi/802.11x Local Loop VoIP handset Ckt-PBX IP-PBX IP-phones ISDN-phones IP-phones DSL/CableIP LAN Wireless Router Base Station 5ESS (IP-Centrex) Office/Hotel HotspotHome On the Road Home/Office Dual-mode WiFi phoneSoft-phones PSTN SS7 SIP Clients Ckt handset Multiple user interfaces with common look and feel Other Clients IMS Converged Communications Services Vision LucentLucent PresencePresence ServerServer ActiveActive PhonebookPhonebook ServerServer BroadSoftBroadSoft TelephonyTelephony ServerServer AnyPathAnyPath UnifiedUnified MessagingMessaging SvrSvr OtherOther App ServersApp Servers (PTT, IM etc.)(PTT, IM etc.) EBS Web PortalEBS Web Portal Parlay/OSAParlay/OSA MediationMediation Gateway (ISG)Gateway (ISG) Network Operations, Applications Mgt, Subscriber registration/ authorization PresencePresence ServersServers PresencePresence ServersServers TelephonyTelephony ServersServers TelephonyTelephony ServersServers UnifiedUnified MessagingMessaging UnifiedUnified MessagingMessaging
- 10. DIT Roles of Standards Bodies for IMS ServicesServices Open Mobile AllianceOpen Mobile Alliance Defining IMS services The Parlay GroupThe Parlay Group Integral to IMS architecture, define standard API frameworks MobileMobile ArchitectureArchitecture 3rd Generation3rd Generation Partnership ProjectPartnership Project Define IMS network elements and infrastructure ArchitectureArchitecture for Wirelinefor Wireline ETSI TISPAN - Merger ofETSI TISPAN - Merger of TIPHON (VoIP) and SPANTIPHON (VoIP) and SPAN (Fixed)(Fixed) Defines SIP, SDP and other protocols underlying IMS IMS is driving some of the work in IETF CornerstoneCornerstone Internet EngineeringInternet Engineering Task ForceTask Force Agreement on reuse of 3GPP IMS in comprehensive NGN plans
- 11. IMS Building Blocks 1. An all-IP Core Network (CN) 2. An all-IP Radio Access network (RAN) 3. Multimedia call control based on SIP 4. Quality of Service (QoS) support for IP
- 12. DIT 3GPP IMS Network Elements HSSHSSHSSHSS I-CSCFI-CSCFI-CSCFI-CSCF S-CSCFS-CSCFS-CSCFS-CSCF Visited Network Home Network SIP ASASASASASASASASASASASAS Home Subscriber Server • Centralized DB • HLR successor • User profile • Filter criteria (sent to S-CSCF) • Which applications • Which conditions Home Subscriber Server • Centralized DB • HLR successor • User profile • Filter criteria (sent to S-CSCF) • Which applications • Which conditions Application Servers • Push-to-talk • Instant messaging • Telephony AS • 3rd party or Lucent Application Servers • Push-to-talk • Instant messaging • Telephony AS • 3rd party or Lucent P-P- CSCFCSCF P-P- CSCFCSCF BackboneBackbone PacketPacket NetworkNetwork BackboneBackbone PacketPacket NetworkNetwork AccessAccessAccessAccess MGCFMGCFMGCFMGCF MGWMGWMGWMGW PSTNPSTNPSTNPSTN H.248 ISUP BGCFBGCFBGCFBGCF SIP SIP SIP SS7SS7SS7SS7 SIP SIP SIP SIP SIP SIP SIP Diameter RTP TDM RTP RTP Call Session Control Function • SIP registration • SIP session setup Call Session Control Function • SIP registration • SIP session setup MRFMRFMRFMRF Media Gateway Control Function • Interfaces to PSTN/PLMN by • Converting SIP <-> ISUP • Interworking RTP to circuit • H.248 control of MGW Media Gateway Control Function • Interfaces to PSTN/PLMN by • Converting SIP <-> ISUP • Interworking RTP to circuit • H.248 control of MGW Breakout Gateway Control Function • Selects network (MGCF or other BGCF) in which PSTN/ PLMN breakout is to occur Breakout Gateway Control Function • Selects network (MGCF or other BGCF) in which PSTN/ PLMN breakout is to occur Media Resource Function Pooling of Media servers Media Resource Function Pooling of Media servers Proxy CSCF • 1st contact point for UE • QoS • Routes to I-CSCF Proxy CSCF • 1st contact point for UE • QoS • Routes to I-CSCF Interrogating CSCF • Entry point for incoming calls • Determines S-CSCF for Subscribers • Hides network topology Interrogating CSCF • Entry point for incoming calls • Determines S-CSCF for Subscribers • Hides network topology Serving CSCF • Registrar • Session control • Application Interface Serving CSCF • Registrar • Session control • Application Interface
- 13. DIT Brief Explanation IMS Network Elements The Call Session Control Function (CSCF) is a SIP server which processes the IMS signaling traffic in order to control multimedia sessions. There are three types of CSCF: Proxy CSCF (P-CSCF): The initial point of contact for signaling traffic in to the IMS. Serving CSCF (S-CSCF): Provides the service coordination logic to invoke the application servers needed to deliver the requested service. Interrogating CSCF (I-CSCF): A SIP proxy that provides a gateway to other domains, such as other service provider networks. The Home Subscriber Server (HSS) is a centralized database storing the subscriber profile information.
- 14. DIT Brief Explanation IMS Network Elements (2) An Application Server (AS) hosts and executes services and can run in a number of classical SIP operational modes. The application servers mentioned above are attached to the S-CSCFs to host and serve IMS services. The Media Resource Function (MRF) comprises two nodes: the Controller and Processor. The MRFC (controller) is situated in the signaling plane as a SIP User Agent; and the MRFP (processor) is situated in the media plane and provides media related functions, such as serving voice announcements, voice mixing (for conferencing) and video conferencing. A Border Gateway Control Function (BGCF) identifies if a session terminates on the PSTN and determines which MGCF should handle it. The Media Gateway (MGW)/Media Gateway Control Function (MGCF) collectively represent equipment that provides interworking with the legacy PSTN.
- 15. DIT IMS Protocol Session Initiation Protocol (SIP): An application layer protocol for establishing, terminating and modifying multimedia sessions within an IP network. SIP has been embraced as the specified protocol in support of session control protocol for IMS which follows a client server model. Session Description Protocol (SDP): is a text based protocol which describes the multimedia session. For example, when initiating a session the caller and callee indicate and exchange their media capabilities as well as receive address and port number. Real-Time Protocol (RTP): provides a mechanism to transport real-time multimedia traffic including video and audio over unreliable transport mediums such as User Datagram Protocol (UDP). Diameter: The Diameter protocol was chosen for use with IMS as the AAA (Authentication, Authorization and Accounting) protocol.
- 16. DIT SIP Protocol IMS builds on the Session Initiation Protocol (SIP), which has emerged as the crucial technology for controlling communications in IP -Based Next-Generation Networks (NGNs). The advantages for adopting the SIP as control layer protocol: Advantages in convergence and interworking of voice and data services Supports the development of IN network towards the application and terminal sides Supports mobility function at the application layer Simple protocol with recognized potential for extension.
- 17. A Typical Example of an IMS Call User B DSL/Cable ModemDSL/Cable Modem DSLAM/CMTS RNC GGSN NetworkZ (UMTS/GPRS)NetworkZ (UMTS/GPRS) NetworkXNetworkX User A SGSN NetworkYNetworkY GRXGRX P-CSCF P-CSCF I-CSCF I-CSCF S-CSCF S-CSCF HSS HSS AS AS
- 18. 18 Imagine starting a voice call on you home phone and transferring it seamlessly to your mobile as you drive to work. Imagine sending a multimedia message from your car that later appears on your TV screen. Imagine watching a movie on that same TV, pausing it in mid- show and then watching it on a wireless PDA as you relax in the garden. Imagine having a cell phone conversation with two or three friends and simultaneously sharing a video of the football match you are attending. Imagine that all of the above can be done with a single account, on a single log-in with multiple devices over any number of access networks These are only a few examples of seamless multimedia services that IMS will allow users to access “anywhere” at “anytime” Why all of the excitement?
- 19. Who needs IMS? Fixed Network Users want Multimedia conferencing: With PC or SIP phone user can participate in a video conference with mobile or WLAN users. Voice over IP: Cable providers will become phone providers. Streaming Services: Video on demand, wake-up call with music video or latest news. Mobile Network Users want Push-to-X: PTtalk, PTVideo. Location Based Services: Which of my friends is nearby? Mobile Gaming: Gaming on your mobile, while you chat with a friend you play against. Network Providers want Fixed Mobile Convergence. A service needs to be implemented only once for all kind of access networks. New business models by offering my services to users from other access networks. DIT
- 20. DIT Why do we need IMS? Challenges in services Difficulty and slowly delivery of new services Single services experience Challenges from Internet Internet has been competitor of legacy operator Legacy operator must learn from Internet Challenges in OPEX/CAPEX More network technologies and more network deployment Duplicated development and deployment leads to higher CAPEX and OPEX Challenges in Average Revenue Per User (ARPU) Voice ARPU is decreasing Difficulty for legacy networks to introduce abundant services and charge for content and service
- 21. DIT Characteristic of IMS - More Convergence Network resource sharing greatly reduces CAPEXOPEX Reduce customer churn and improve loyalty Unified services deliver any application to any terminal Multimedia experience Single user profile, single sign on FixedNetwork MobileNetwork MobileData Internet Multi-Service Traditional Network Converged Network Convergence Terminal IP Connectivity GSM/UMTS Broadband WLAN Services & Content Session Control
- 22. DIT User-Centric Network User-centric network: One network for all services Single Sign-On IMS Service-centric network: Services provided by different network. Sign-On for each service; Services Address book Profile Bill My rings Profile Address book Bill User identity, profile, address book and bill are different by each service; Services can’t be customized, or difficult to be customized. One user identity, one profile, one address book and one bill for all services Customized services
- 23. Benefits of IMS User experience in mobility and multimedia Richer services Abundant and attractive services will boost ARPU Sustained service revenue Telecom Operators will generate much more revenue by operators always be on top of IP service value chain Common shared subscriber data Better investment protection Common IMS Core infrastructure and service Enablers will remain unchanged when new services and access types are introduced. Initial network investment on IMS Core will be protected during later stages of network deployment DIT
- 24. DIT Subscribers want access to communications services from many places… Home, office, or on-the-go: mobility isn’t just wireless voice anymore! from several devices… Telephones, PCs, mobile phones, PDAs without needing separate accounts Single sign-on, common contacts, and “access-aware” information delivery Home Office Moving Travel Convergence Networks Fixed Networks Mobile Networks Benefit of IMS-User Experience: Wider Mobility
- 25. DIT Benefit of IMS-User Experience: Multimedia Today Limited video introduced Yesterday voice leading Tomorrow User-centric multimedia experience 1.Hi, I am Robert Let us have a talk about our next film 2.Hi, I am Richard Rich voice, VoD, internet applications, etc Still can not flexibly add/drop multiple media types, or switch between them within single session
- 26. DIT IP Backbone IMS Core Presence Chat Media Push Game CALL WHITEBOARD Rich Call Push To Talk 6 Video Music Voice Enterprise AD Cartoon Greeting Play Your True Color Multimedia RBT Benefit of IMS - Richer Services
- 27. DIT Benefits of IMS - Sustained Service Revenue RAN SGSNSGSN GGSNGGSN RAN SGSNSGSN GGSNGGSN ApplicationsApplications HSSHSS CSCFCSCF RAN SGSNSGSN GGSNGGSN Internet ApplicationsApplications Domain Controlled by Operator Operator risks itself to be a bit pipe IMS PS only Domain Controlled by Operator End-to-End service control
- 28. DIT Benefits of IMS - Common Shared Subscriber Data Replicated Data HSSHSSHSSHSS Now IMS SESSION CONTROL Application 1Application 1 Application 2Application 2 Application XApplication X Application 1Application 1 Application 2Application 2 Application XApplication X
- 29. DIT NAT controlAuth SigComp Routing Charging New EnablerMessaging Conference Presence Group Mngt Common Functions Service Enablers QOS Control Service Trigger Broadband WLANGSM/UMTS CDMA2000 Application1 Application2 Application3 More Apps Benefits of IMS - Better Investment Protection
- 30. DIT V2 CC - Seamless Multimedia communication Single Number for both GSM/UMTS and WLAN/WiMAX Bi-directional smooth handover: less than 200ms, no interruption Excellent voice quality: better than GSM Multi-media service enabled Application & ServiceApplication & Service IMS VCC IMS core network Public/Private WiFi/WiMAX newtwork Cellular Network Indoors Outdoors Voice Call Continuity VCC Application Server
- 32. DIT
Notes de l'éditeur
- Media Gateways are the interface between IMS and the legacy PSTN world. This allows calling between the richly featured multimedia IMS environment to the existing voice networks. The interworking between legacy endpoints and the IMS network allow those endpoints to access the features and functions that IMS can provide. Of course, this functionality may be limited by the capabilities of the endpoint. For example, network based features may be available to the legacy endpoint, but not multimedia. IMS defines common support for Classes of Service, Quality of Service, security and other attributes. However, standards are still evolving in many of these areas. Since IMS is built upon IP, it supports the flexibility and scalability to support mobility, portability, service creation, etc. All of these together may provide operational and financial improvements beyond existing networks. IMS defines how to develop subscriber databases which include User Profiles that enumerate identity, services, security levels, etc. IMS defines common session control that applies to any media. So the way a voice call is set up is identical to how a video call is set up. Based upon the class of service, different resources may be allocated in the network. IMS specifies common OAM&P environment that allows the evolution of operation support systems. IMS, in its self, does not define services. However, it defines how services are accessed. These services may be inherent in the IMS network or can provide gateways to existing service platforms.
- IMS is designed to be applicable to the evolution of all types of networks. The major wireless carriers have committed to IMS as their next generations network. All of the U.S. major wireline carriers have embraced IMS in their evolution path. Cable network companies have not embraced IMS as of yet since Cable Labs has just defined IP-based network topology that was pre-IMS. It is thought that as cable networks evolve, they too will embrace IMS. One major advantage of IMS’s commonality is that carriers from each discipline can purchase equipment based upon the same standards, thereby potentially decreasing the cost to provide duplicate networks for different media services.
- IMS is being defined as the convergence vehicle for all types of access connectivity. IMS allows typical Centrex customers to migrate to IP-based Centrex services and provides direct connectivity from the myriad of IP PBXs that are being deployed. IMS provides a natural evolution as LECs deploy their broadband access to the home as well as providing cable providers a standardized approach for network evolution. This theme extends to the introduction of WiFi or WiMax technologies that are inherently IP based. It is recognized that not all end points will be SIP enabled. Therefore, legacy systems can take advantage of the IMS services by entering the network through signaling and media gateways. As shown in the wireless cloud, a network can evolve such that it can take advantage of existing access techniques while evolving to IP connectivity that can natively interconnect to the IMS core.
- UE sends SIP INVITE, which is tunneled through the RAN and BPN, to the P-CSCF. P-CSCF queries DNS for the address of a CSCF in the home network. P-CSCF forwards SIP INVITE to the I-CSCF in the Home Network I-CSCF retrieves the information needed to select the S-CSCF. I-CSCF forwards SIP INVITE to the S-CSCF in the Home Network. S-CSCF retrieves authentication vectors from the HSS, and selects one of the vectors. A “SIP 401 unauthorized” is sent back to the UE with authentication data. This message rejects the initial REGISTER. UE sends a new INVITE, with authentication data calculated by the UE, to the S-CSCF. The message flow is similar to steps 1 through 5. The S-CSCF performs authentication. If authentication is successful, the name of the S-CSCF is stored in the HSS. S-CSCF retrieves profile information and filter criteria from the HSS over the Cx interface. S-CSCF sends SUBSCRIBE message to the P-CSCF.
- This example illustrates how IMS multimedia calls may be coordinated between parties. The first is a voice call originated by User A. The second is a video call originated by User B and the third is a data call originated by User A. The voice call originates from user A and enters the IMS network X at the P-CSCF The P-CSCF passes the call to the S-CSCF The S-CSCF interrogates the Application Server for originating services The S-CSCF forwards the call to the I-CSCF of network Y. The I-CSCF interrogates the HSS to determine the S-CSCF and passes the call to it. The S-CSCF interrogates the Application Server for terminating services. The S-CSCF passes the call to the P-CSCF assigned for the user and the voice call is completed. Now a video call is set up from User B to User A and the signaling path is reversed. Finally, User A sets up a data call to User B using the same signaling path.
- Complex and Close Service Environment Too complex Service Creation Environment The 3rd AS can’t be introduced Operator have to upgrade the network nodes to support new services Separated Networks Different network for different services Common service enablers can’t be shared Simple services, simple experience - IP over everything Everything over IP - Much lower cost With wider bandwidth, it can support some real-time service Client-to-Server mode Fast provide abundant services Simplify network Multimedia user’s experience
- The legacy services are provides by different networks. Each service has its different profile, and user shall sign on to each services. IMS focus on user only have one identification, one profile, one address book, and single sing-on. What more, use can customize every service. Such as ring back tone, call ID, smart routing etc. One fundamental assumption is that the business landscape in coming years will contain a wide variety of person-to-person and person-to-content applications, sometimes handled and managed individually by the end user, but probably normally bundled and provided by the operator or operator federations. Obviously, the end users expect convenience and ease of use; one major element here is the ability to provide Single Sign On functionality
- 用户体验：多种终端应用开发
- PS only：管道命运
- SIP Modularity IMS is based on SIP. SIP is very modular. Many different functions supported by SIP are separate, modular, orthogonal components, which over time can be swapped in and out of IMS. This is especially important when mechanisms for accomplishing these functions will evolve over time. The QOS The authentication Signaling Compression A key feature of SIP is its ability to separate the notion of a session from the protocol used to invite a user to a session. SIP just issues invitations; it does not know anything about the session itself. The Benefit： IMS is a future-proof architecture. Network Capability Extension very easy. The core network is not changed when new services and new mechanisms are introduced. Common Function IMS core network provide common function by defining how service requests are routed, how charging is performed, how QOS is assured and how service composition is enabled. The CSCF don’t support service logic. The CSCF can route SIP messages very effectively. Benefit Provide a Unified routing mechanism, service interoperability is supported. Enable the service can be decomposed. Enables operators eliminate the costly and complex traditional network structure of overlapping functionality for charging, routing and provisioning. Service Enabler Service enabler: A service in the IMS service framework that can be used as basic building block functionalities giving support to other Application Server in order to create more complex services. IMS facilitates the creation and delivery of multimedia services based on service enabler. Presence Group List Management Messaging Server Benefit: Service enablers: Write once, use many The enablers developed for successful applications can become ’global enablers’ that are automatically included in new applications and services.
- GSM/UMTS and WiFi multi-mode terminal can make telephony calls with VoIP via WLAN access, or with CS voice via GSM/UMTS access, in order to achieve cheaper tariff and better coverage; Solution compliant with 3GPP Rel7 VCC specification standard, with IMS domain HOAS as the anchoring point; Same MSISDN number can be shared for WiFi and Cellular coverage for the same subscriber; Bi-directional in-call handover between CS and IMS with excellent performance supported; Multimedia and IP Centrex services can be enjoyed by end users over WiFi access;