Table of Content. Introduction Components Architectural Characteristics Concepts Protocols Service Examples Discussion. ToC

Transcription

1 Danar Barzanji Marcel K Steffen Roger Trösch Communication Systems IMS

2 Table of Content Introduction Components Architectural Characteristics Concepts Protocols Service Examples Discussion # 2 ToC

3 Definition of IMS IMS = IP Multimedia Subsystem Standardised (3GPP) Next Generation Network (NGN) It supports data, video, SIP-based VoIP and non- SIP packetised voice calls # 3 Introduction

4 3GPP 3rd Generation Partnership Project (3GPP) It co-operates with - ETSI (European Telecommunications Standards Institute Europe) - ARIB/TTC (Association of Radio Industries and Business / Telecommunication Technology Committee - Japan) - CCSA (China) - ATIS (Alliance for Telecommunications Industry Solutions - North America) - TTA (Telecommunication Technology Association South Korea) Frequently releases of standardization documents (current Release 7) # 4 Introduction

5 Evolution of Mobile Networks 1G First generation wireless telephone technology (analog) e.g.: NATEL C (1987) 2G Second generation wireless telephone technology (digital) e.g.: GSM 900/1800 (1992) 2.5G 2G with packet switched domain e.g.: GPRS 3G Third generation technology e.g.: UMTS # 5 Introduction

6 Components Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 6 Components

7 Call Session Control Function (CSCF) Proxy-CSCF - fist point of contact for user equipment - functions: security, verification, policy decisions Interrogating-CSCF - contact point within operator s network - functions: forwarding requests, response to S-CSCF, topology hidding of home network Serving-CSCF - central point of signalling - handles registration and service requests # 7 Components

8 Databases HSS & SLF Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 8 Components

9 Databases HSS & SLF Home Subscriber Server - central repository of all data of subscriptors - required for session establishing & providing services - contains: identification-, security-, location- and user profile information Subscription Locator Function - obtains queries about users addresses - provides requestor with all related information # 9 Components

10 Interworking Elements Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 10 Components

11 Interworking Elements Breakout Gateway Control Function (BGCF) - only used from IMS originated calls into a CS domain - can report account information and collect statistical information Media Gateway Control Function (MGCF) - protocol convertion and mapping of SIP between IMS and CS domain Signaling Gateway (SGW) Media Gateway (MGW) # 11 Components

12 Application Server Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 12 Components

13 Application Server The application servers offer multimedia services Three different AS categories: - SIP AS: SIP based multimedia applications - OSA-SCS (Open Service Access Service Capability Server): offers functionalities like call control, user interaction, user status etc - IM-SSF (IP Multimedia Service Switching Function): allows to use services that were designed for GSM # 13 Components

14 Media Resource Function Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 14 Components

15 Media Resource Function MRF provides home network with source of media Media Resource Function Controller (MRFC) - interprets SIP signalling from S-CSCF for creating and scheduling ad-hoc conference sessions and alter conference members Media Resource Function Protocol (MRFP) - enables manipulation in connectivity layer - performs mixing of incoming streams, media stream source and media stream processing # 15 Components

16 Support Entities Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 16 Components

17 Support Entities Policy Decision Function (PDF) - responsible for policy decisions - decisions based on session and media related infromation Topology Hiding Inter-network Gateway (THIG) - signalling-based hiding of configuration, capacity and topology of the network from the outside Security Gateway (SEG) - tunnels data in encapsulated security payloads (ESP) - is part of the network domain security # 17 Components

18 Access Entities Source: Cisco: Cisco Service Exchange Framework: Supporting the IP Multimedia Subsystem, Cisco, # 18 Components

19 Access Entities Possibilities to access an IMS: GRPS / UMTS access: using Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) WLAN access: using Wireless LAN Wireless Access Gateway (WLAN WAG) and Wireless LAN Packet Data Gateway (WLAN PDG) DSL access: using Digital Subscriber Line Access Mulitplexer (DSLAM) and Base Station (BAS) # 19 Components

20 Architectural Characteristics The basic requirements to achieve the fundamental IMS idea are: Support of IP Multimedia Sessions Support of Quality of Service (QoS) New charging arrangements Access independence Support of interworking and roaming # 20 Architecture

21 IP Multimedia Session IPv6 as the basic protocol IPv6 IPv4 interworking Example of an IMS access in case of roaming Source: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004 # 21 Architecture

22 Quality of Service Problem: Standard internet has delay and lost / disordered packets --> problem with voice / videocall Solution: Reservation of sufficient resources for each service / user. In the case of roaming: Service level-agreements (SLA) are required # 22 Architecture

23 Charging (1/2) Two different charging methods: Online charging: realtime interaction with user s account Two different methods: Event charging & session charging Source: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004 # 23 Architecture

24 Charging (2/2) Offline charging: charging progress starts when a service has stopped # 24 Architecture Source: Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004

25 Access Independence Different possibility to access an IMS: GPRS UMTS CDMA2000 WLAN WiMAX DSL Cable Circuit-switched networks (PSTN, ISDN) # 25 Architecture

26 Interworking / Roaming IMS guarantees interworking between PSTN ISDN GSM Other technologies not developed by the 3GPP User can connect to their Home-IMS in visited networks # 26 Architecture

27 Concepts Registration IMS Entry Point Private/ Public Identity IMS Identity Module (ISIM) Security Connectivity to non-ims User # 27 Concepts

28 Registration Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004 # 28 Concepts

29 IMS Entry Point DHCP s Domain Name System (DNS) - DHCP query to IP connectivity access network - relay to DHCP server - returns either list of SIP server domain names or SIP server IPv6 addresses of P-CSCFs GPRS method - PDP context request to SGSN - relay to Gateway GPRS Support Node (GGSN) - returns IP address of entry point # 29 Concepts

30 Private/ Public Identity Private Identity: - defined by home network - unique network access identifier (NAI) - securely stored in IMS Identity Module (ISIM) - only used for registration, not for SIP messages Public Identity: - can be published - either form of SIP URI (e.g. [email protected]) or tel URI (e.g ) # 30 Concepts

31 IMS Identity Module (ISIM) Part of Universal Integrated Circuit Card (UICC) Contains six different submodules: ISIM Security keys Public user identity Access rule reference Private user identity Home NW domain name Administrative data UICC # 31 Concepts

32 Security Security Key (shared by ISIM & AUC) IP-based traffic using IP security (IPSec) Security Gateway (SEG) for transfer between two security domains with encapsulated security payload (ESP) SIP protected with transitiv trust domains # 32 Concepts

33 Connectivity to non-ims User MGCF performs mapping of SIP to the call controll in CS networks MGW translates the two different protocols Poikselkä, M.; IP Multimedia Concepts and Services in the Mobile Domain, John Wiley & Sons, 2004 # 33 Concepts

34 Protocols Protocol categories SIP (Session Initiation Protocol) Use of SDP in SIP Use of SIP in IMS IMS-Media Plane Protocols Authentication and security protocols # 34 Protocols

35 Protocol Categories Protocols can be classified in three categories: Signalling or session control protocols - SIP Media plane protocols - RTP and RTCP Authentication and security protocols - Diameter # 35 Protocols

36 SIP (Session Initiation Protocol) An application layer signalling protocol that defines initiation, modification and termination of interactive, multimedia communication sessions between users. (IETF RFC 2543 Session Initiation Protocol) Core protocol in IMS network # 36 Protocols

37 SIP Properties Text-based protocol Extensible protocol - Adding new headers Based on Request-response transaction model Session types: - One-to-one voice call - One-to-many multimedia conference Peer-to-peer protocol Messages use either UDP or TCP # 37 Protocols

38 SIP-Architecture and Components SIP Servers SIP User- Agents SIP Gateways Voice over IP IETF Standard SIP, Datus AG, 2004 # 38 Protocols

39 SIP User Agent An application that initiates, receives and terminates calls User Agent Clients (UAC) An entity that initiates a call User Agent Server (UAS) An entity that receives a call Both UAC and UAS can terminate a call # 39 Protocols

40 SIP Servers (1) Proxy Server: intermediate entity receives a SIP request, forwarding or responding to the request has access to a database two types: - Stateless Proxy (I-CSCF, no memory of any request or response) - Stateful Proxy (P-CSCF performs stateful proxy) # 40 Protocols

41 SIP Servers (2) Redirect Server - Redirects SIP requests to UA - Maps address into zero or more new addresses and return them to UA Registration Server - Accepts REGISTER requests - May support authentication - S-CSCF performs this functionality # 41 Protocols

42 SIP Gateways An application, that interfaces a SIP network to a network utilizing another signalling protocol # 42 Protocols

43 SIP Messages-Methods and Responses SIP Methods: INVITE Initiates a call by inviting user to participate in session. ACK - Confirms that the client has received a final response to an INVITE request. BYE - Indicates termination of the call. CANCEL - Cancels a pending request. REGISTER Registers the user agent. OPTIONS Used to query the capabilities of a server. SIP Responses; 1xx - Informational Messages. 2xx - Successful Responses. 3xx - Redirection Responses. 4xx - Request Failure Responses. 5xx - Server Failure Responses. 6xx - Global Failures Responses. # 43 Protocols

44 SIP Headers SIP borrows much of the syntax and semantics from HTTP A SIP messages looks like an HTTP message message formatting,header and MIME support SIP Header INVITE sip:5120@ SIP/2.0 Via: SIP/2.0/UDP :5060 From: sip:5121@ To: <sip:5120@ > Call-ID: c e0563-2a1ce-2e323931@ CSeq: 100 INVITE Accept: application/sdp Contact: sip:5121@ :5060 Content-Type: application/sdp # 44 Protocols

45 SIP Addressing The SIP address is identified by a SIP URL in the format: user@host Examples of SIP URLs: - sip:[email protected] - sip:hostname@ sip: @vovida.org # 45 Protocols

46 Use of SDP in SIP SDP (Session Description protocol) - Describes the media content of session - Content contains: IP Address Port number Media type Media encoding schema Default message type in SIP is application/sdp # 46 Protocols

47 Use of SIP in IMS (1) - new parameters IMS defines extensions to headers and parameters to address specific needs - Auth-param for WWW-authenticate - Tokenized-by for carrying encrypt/decrypt string - icn-charging-info for P-Charging-Vector header - New parameter defined for P-Access-Network- Info # 47 Protocols

48 Use of SIP in IMS (2) P-Headers IMS introduced several Private Headers (P-Headers) into IETF to meet telephony needs. P-Headers are optional extensions to SIP. - P-Asserted-Identity - P-Called-Party-ID - P-Access-Network-Info - P-Visited-Network-ID - P-Associated-URI - P-Charging-Function-Addresses - P-Charging-Vector # 48 Protocols

49 IMS - Media Plane Protocols (1) RTP (Real-time Transport Protocol) - defines a standardized packet format for delivering audio and video over the Internet - Layer four, or application layer - Uses UDP for transport over IP RTCP (RTP Control Protocol) - Generates Quality of Service (QoS) statistic - performs the mapping between the RTP timestamps and a reference a clock important in video conferencing application COPS (Common Open Policy Service Protocol) - To Ensure # 49 Protocols

50 IMS - Media Plane Protocols (2) COPS Common Open Policy Service Protocol - to ensure QoS - enables the communication of QoS and other traffic policy information between a policy server and clients - used in Go reference point # 50 Protocols

51 Authentication and security protocols Diameter is an authentication, authorization and accounting (AAA) protocol developed by the Internet Engineering Task Force - lets IMS devices access the HSS and then provide the necessary authentication, authorization - provides billable communications accounting services # 51 Protocols

52 Service Examples Video Call / Conferencing Push-to-Talk Instant-/ Voice Messaging Real-time Video Sharing telematicstech.com Interactive Applications # 52 Service Examples

53 Video Call / Conferencing Call: point-to-point service Conference: multi-point service - ad-hoc with SIP - scheduled with conference policy control protocol (CPCP) nokia.com # 53 Service Examples

54 Push-to-Talk Standard: PoC Standardised by OMA Like walkie-talkie Half-duplex service Voice packets transmitted by RTP 3C.co.uk # 54 Service Examples

55 Instant-/ Voice Messaging Instant Messaging: - pager-mode (Release 5) - session-based (Release 6) Voice Messaging - content is an audio file - faster for user - more personal microsoft.com # 55 Service Examples

56 Real-time Video Sharing SIP-based multimedia streaming Peer-to-Peer service Both circuit- and packetswitched connection spontaneous sharing of experiences, sourroundings and information fotojive.com # 56 Service Examples

57 Interactive Applications Interactive gaming (over IP multimedia core) Sharing of personal data (e.g. calendar information, contact details, etc.) 3gamericas.com # 57 Service Examples

58 Conclusion Advantages: - Combining the latest in technologies - Creating a commoin platform to develop diverse multimedia - Boost margin due to extra usage of packet-switched networks New benefits and services: - Quality of Service (QoS) - Different charging models - IP based technology - Access independence, Interworking # 58 Conclusion

59 # 59

60 Discussion 1 Architecture Why using a new architecture for services that are already offered by the internet. # 60 Discussion

61 Discussion 2 Architecture IMS integrates different networks... Why not building a new network based on a single technology? # 61 Discussion

62 Discussion 3 Video calling Do we need video calling? What are the advantages and possible disadvantages? # 62 Discussion

63 Discussion 4 Services/ Applications What kind of services/ applications can you imagine to use? # 63 Discussion

64 Discussion 5 PC vs. Mobile Are you willing to game against/ or make a video call to a mobile user while you are sitting in front of your PC? # 64 Discussion

65 Thanks For Your Attention! Danar Barzanji Marcel K Steffen Roger Trösch Communication Systems IMS