Broadband Telecommunications and Networks

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1 정보통신망의기초 12. IMS(IP Multimedia Subsystem) / Part Jeong-Gyu Lee

2 What is IMS? IP Multimedia Subsystem [IMS] is an architectural framework for delivering IP multimedia services to end users. IMS provides a network-independent, common service delivery environment for both wireless and fixed network users. IMS standards define common signaling and media interfaces that are open, vendor independent, and abstract the underlying network complexities. 2

IMS Overview - Standards 3GPP has developed IMS for delivering Internet Services over GPRS 3GPP2 is defining requirements for support of CDMA2000 TISPAN is defining the NGN network based on 3GPP IMS

3 IMS Overview - Standards 3GPP has developed IMS for delivering Internet Services over GPRS 3GPP2 is defining requirements for support of CDMA2000 TISPAN is defining the NGN network based on 3GPP IMS and adapting 3GPP IMS to fixed access networks OMA is defining services based on the 3GPP IMS service platform IETF standards such as SIP is fully utilized for IMS to ease the integration with the Internet 3GPP : 3 rd Generation Partnership Project TISPAN : Telecom & Internet converged Services & Protocols for Advanced Network OMA : Open Mobile Alliance 3

4 Convergence and IMS Drivers Convergence Fixed, mobile, broadband Convergence is a reality IMS motivations New services and revenue Fast time-to-market Harmonized (any terminal) Lower infrastructure cost IMS technology components IP (while keeping legacy) SIP Multimedia high compression/ quality and adaptation Any access and IMS arch support BROADBAND FIXED IMS MOBILE 4

5 Service Convergence Pre-IMS Communications (Service Islands) IMS Communications (Integrated Services) 5

6 User Connectivity Services Network Convergence (or Fixed-Mobile Convergence) Services Location/Auth IMS HSS Core FIXED MOBILE Access xdsl WiMAX WLAN GERAN WCDMA 6

7 IMS Evolution IMS evolved from early packet data over mobile wireless architectures called 3G.IP to provide internet services over mobile networks. IMS was incorporated into 3GPP standards efforts first appearing in Release 5. IMS was incorporated into 3GPP2 standards efforts as part of Multimedia Domain [MMD]. ETSI-TISPAN and ITU-T also incorporated IMS into their Next-Generation-Network [NGM] Wireline standards developments. Other consortia such as OMA are involved in specifying IMS services. 7

8 IMS Standards (1) Rel. 4.0 Rel. 5.0 IMS Rel. 6.0 IMS Rel. 7.0 IMS Rel. 0 MMD Rel. A MMD Rel. 1.0 NGN Rel. B MMD Rel. 2.0 NGN Rel. 1.0 NGN FG OMA Other * IP multimedia subsystem (IMS), multimedia domain (MMD), Next Generation Network (NGN) 8

9 IMS Standards (2) Rel. 7.0 Rel. 8.0 Rel. 2.0 Rel. 3.0 NGN NGN Rel. 2.0 NGN FG * IP multimedia subsystem (IMS), multimedia domain (MMD), Next Generation Network (NGN) 9

10 Release '99 3GPP: Standards Releases functionally frozen December Defines UTRA and many other initial features The basis for early 3G deployment Release 4 functionally frozen March Enhancements to Release '99 plus separation of control plane from user plane in core network First steps towards IP-based operation Also defines the low chip rate TDD mode (TD-SCDMA) Release 5 functionally frozen March/June This release introduces: IMS - IP-based Multimedia Services HSDPA - High Speed Downlink Packet Access Release 6 functionality frozen September/ December2004 Includes 2nd phase of IMS, High Speed Uplink, plus many other features designed to deliver the full 3G experience Release 7 Stage 1: Dec 2005; Stage 2: 2 nd half 2006; Stage 3: mid-2007 Enhanced uplink, other spectrum; multiple input multiple output antennas (MIMO), Advanced Global Navigation Satellite System concept, IMS emergency call handling, e-call, back-up algorithms (UEA2 and UIA2) 10

11 Services and Control What IMS Provides Adds call session control to the packet network Enables peer-to-peer real-time services - such as voice, video - over a packet-switched domain Mixed Multimedia Ability to pick and mix various multimedia flows in single or multiple sessions Can handle real-time voice, video, data Connectivity Independence Provides access to IP based services independent of the connectivity network: mobile (3GPP s UMTS, 3GPP2 s CDMA2000) and fixed networks (TISPAN s NGN) 11

12 PoC service IMS Application Examples PoC (Push-to-Talk over Cellular) A walkie-talkie type service that provided over a cellular phone network Half duplex communications while one person speaks, the other(s) listen Immediate and instant communication Video and text as well as voice Open standard-based (OMA) 12

13 IMS Application Examples Video Sharing Video Sharing Sharing one-way live video or video clips in real time during a normal voice call Enhances a voice call with the ability to share video among users New opportunity for mobile operators to gain additional revenue from voice calls Prolonged voice call duration Open standard based (GSMA) 13

14 IMS Application Examples Video Sharing (From Nokia s WP) 14

15 IMS Application Examples VCC(Voice Call Continuity) Voice Call Continuity Seamless Handover between Wi-Fi and CDMA/GSM IMS Application Server 3GPP VCC AS 3GPP2 TS TS X.P0042 Handover Wi-Fi Access VCC AS IMS Core IP Core Network MGCF MGW Anchoring and Switching at VCC AS WiBro 1x OEP OEP (other end point) CDMA 1x MSC Dual-Band Handset Device 15

16 IMS Architecture - Overall 16

17 IMS Architecture - Simplified 17

18 Access Network 접근방식분류 Components (1) Fixed access: DSL, cable modem, Ethernet Mobile access: W-CDMA, CDMA2000, GSM, GPRS Wireless access: WLAN, WiFi, WiMAX IMS 단말들은다른지역이나국가 (visited network) 에서 roaming 중일때도 IMS 망을사용할수있음 기존의 analog 전화서비스, H.323, 비 IMS VoIP 와같은시스템들도 gateway 를통해 IMS 에접근가능 18

19 Core network Components (2) Home Subscriber Server (HSS) User Profile Server Function (UPSF) 라고도함 IMS 망에서직접 call handling을하는 entity들에게가입자정보를제공하는 DB 가입자인증, 권한부여기능수행, 가입자의물리적인현재위치정보제공 기존이동통신망의 Home Location Register (HLR) 나 Authentication Centre (AuC) 역할 가입자확인 일반적인 3GPP 망은다음과같은방법을사용 International Mobile Subscriber Identity (IMSI): SIM에저장되는 unique phone identity Temporary Mobile Subscriber Identity (TMSI): privacy 보장을위해지리적위치에따라생성됨 International Mobile Equipment Identity (IMEI): 단말에부여된 unique device identity Mobile Subscriber ISDN Number (MSISDN): 가입자의일반전화번호 IMS에는 IP Multimedia Private Identity (IMPI) 와 IP Multimedia Public Identity (IMPU) 가추가됨 전화번호나숫자의나열이아닌 URI로되어있음 숫자형태나 (tel-uri, e.g. tel: ) 문자형태를 (sip-uri, e.g. 가질수있음 하나의 IMPI에여러개의 IMPU가있을수있음 하나의 IMPU를여러단말이공유가능 (e.g. 가족전화번호 ) HSS는 IMPU, IMPI, IMSI, MSISDN, 기타정보를저장하고있음 19

20 Core network Subscriber Location Function (SLF) Components (3) 여러개의 HSS가사용중일때가입자 address mapping 수행 HSS와는 DIAMETER protocol을사용하여통신 Call/session control SIP server나 proxy의역할을 Call Session Control Function (CSCF) 에서가지고있으며 IMS의 SIP signalling packet을처리 Call/session control 기능을 P-CSCF, S-CSCF, I-CSCF에서나누어처리 Proxy CSCF (P-CSCF) IMS 단말이가장먼저접속하게되는 SIP proxy 단말이현재속해있는망이 IMS 망이면현재망의 P-CSCF 에접속하고, 그렇지않으면 home network 의 P-CSCF 에접속 단말이 IMS 망에 registration 할때할당되며 unregister 될때까지바뀌지않음 모든 signalling message 가거쳐가게되면이들을모두감시할수있음 가입자인증을수행하고단말과 IPsec 을사용하여연결됨 Spoofing 이나 replay 공격으로부터안전하고가입자의 privacy 가보장됨 다른 node 들은 P-CSCF 를믿고특별한가입자인증을다시수행하지않음 과금기록생성 Policy control, 대역폭관리등을수행하는 Policy Decision Function (PDF) 을포함하기도함 20

21 Serving CSCF (S-CSCF) Components (4) Session control 을수행하며 signalling plane 의중심이되는 node 항상 home network 에위치 가입자정보는저장하고있지않으며필요한경우 DIAMETER protocol 을사용하여 HSS 와 interface 하여 up/download SIP registration 을관장하여가입자의 IP 주소와같은실제위치와 SIP 주소를연결 모든 signalling message 가거쳐가게되면이들을모두감시할수있음 가입자가사용하고자하는서비스를제공받도록하기위해서어느 application server 로 SIP message 를전달할것인지결정 Electronic Numbering (ENUM) 검색을사용하여 routing service 제공 부하분산, 안정성등의문제로하나의망에여러개의 S-CSCF 가있을수있으며, 이런경우가입자가어느 S-CSCF 를사용할것인지는 HSS 가결정 21

22 Interrogating CSCF (I-CSCF) Components (5) 관리 domain 의가장자리에위치하는 SIP function 다른 server들이찾을수있도록자신의 IP 주소를해당 domain의 DNS에등록 Server들은 I-CSCF를해당 domain으로 SIP packet을보내기위한 forwarding point로사용 I-CSCF는가입자의위치를알아내기위해 HSS와 DIAMETER protocol을사용하여통신 어느 HSS 와 interface 해야하는지알기위해 SLF 와통신 가입자에대한정보를알아내면이후에수신되는그가입자와관련된 SIP message들을해당 S-CSCF로전달 IMS release 6까지는외부로부터망내부를감추는역할을수행 Topology Hiding Inter-network Gateway (THIG) 라고불림 Release 7부터는이런 entry point 기능이 Interconnection Border control Function (IBCF) 로분리 IBCF 는외부망으로의 gateway 역할을하며 NAT, firewall 기능을제공 22

23 Application servers (AS) Components (6) SIP를사용하여 S-CSCF와통신하면서 service를제공 제공하는 service에따라 AS는 SIP proxy mode, SIP User Agent (UA) mode, Back-to-Back User Agent (B2BUA) mode로동작 AS의위치는 Home network일수도있고외부의 3rd party network일수도있음 Home network에있는 AS는 DIAMETER protocol을사용하거나 (SIP-AS) Mobile Application Part (MAP) 을사용하여 (IM-SSF) HSS에직접접근 SIP-AS: native IMS application server IM-SSF: IP Multimedia Service Switching Function Customised Application for Mobile networks Enhanced Logic (CAMEL) AS 와통신 기존지능망과연동을위한기능 23

24 Media servers Components (7) Media Resource Function (MRF) Voice stream mixing과같은 media 조작이나 tone, announcement 송출등의기능을제공 Media Resource Function Controller (MRFC) 와 Media Resource Function Processor (MRFP) 로나눌수있음 MRFC: S-CSCF와연동하여 SIP UA로동작하는 signalling plane node이며 H.248 protocol을사용하여 MRFP를제어 MRFP: 모든 media 관련기능을수행하는 media plane node Media resources IMS core function 의제어를받으며 media plane 에서동작 Media Server (MS) 나 Media Gateway (MGW) 와같은것들이있음 Breakout Gateway Breakout Gateway Control Function (BGCF) 전화번호를기반으로한 routing service를제공하는 SIP server IMS로부터 PSTN 과같은 CS 망으로전화를거는경우에만사용 24

25 PSTN gateways Components (8) PSTN과같은 CS 망과 IMS 간의차이 Signalling CS 망 : ISUP or BICC over MTP IMS: SIP over IP Media CS 망 : Pulse Code Modulation (PCM) IMS: Real-time Transport Protocol (RTP) Signalling Gateway (SGW) CS 망의 signalling plane과 interface Stream Control Transmission Protocol (SCTP, IP protocol) 과 Message Transfer Part (MTP, SS7 protocol) 사이의변환을수행하여 MGCP로부터받은 ISUP message를 CS 망으로전달 Media Gateway Controller Function (MGCF) SIP와 ISUP 사이의 call control protocol conversion을수행하고 SCTP를사용하여 SGW와 interface H.248 protocol을사용하여 media gateway를제어 Media Gateway (MGW) CS 망의 media plane과 interface하여 RTP와 PCM사이의변환을수행 양쪽의 codec이서로맞지않으면 transcode 수행 25

26 IMS Architecture REGISTER Flows 26

27 IMS Architecture Session Setup Flows (1) 27

28 IMS Architecture Session Setup Flows (2) 28

29 IMS Architecture Session Setup Flows (3) RTP 29

歯I-3_무선통신기반차세대망-조동호.PDF

歯I-3_무선통신기반차세대망-조동호.PDF KAIST 00-03-03 / #1 1. NGN 2. NGN 3. NGN 4. 5. 00-03-03 / #2 1. NGN 00-03-03 / #3 1.1 NGN, packet,, IP 00-03-03 / #4 Now: separate networks for separate services Low transmission delay Consistent availability