IMS
TPC
EPC
IP Multimedia System: general aspects and migration perspectives
Dr. Leo Lehmann Federal Office of Communication, Switzerland
ITU Workshop on “Developments regarding telecommunication network architectures and services”, Kampala 2 April 2012 Content IMS definition & features IMS history IMS basic architecture IMS & UMTS/ LTE networks IMS registration and session setup IMS Billing IMS centralized services IMS & NGN IMS migration scenarios Further information
IMS definition & features
The IP Multimedia Subsystem is an architectural framework for delivering Internet Protocol (IP) multimedia services
Do we really need the IMS? Not just for enabling IP services in mobile networks B U T for
Combination session establishment with QoS/ security provision (enjoy rather than suffer)
Means for appropriate charge of multimedia sessions (e.g. flat rate, time/volume based, QoS based)
combination & integration of different type of (multimedia) services (own, 3rd party) by standard interfaces
Inhering services like VoIP, Video, IM
IMS definition & features cont.
Overlay for fixed and mobile IP based networks; merging the cellular world with the internet Abstraction from underlying network Multimedia Services Fix/ mobile convergence
Interoperability with CS mobile IMS networks (MAP)
Roaming/ location awareness (IP domain) Packet Data Networks Common control platform GW SIP service enabler CS NW Based on SIP (IETF), Diameter (IETF), H.248 (ITU-T) IMS history (some highlights)
3GPP Release 5: Introduction of SIP based IMS Mobile Multimedia over IP (new applications) End 2 end QoS Voice over MSC server/MGW
3GPP Release 6 IMS phase 2 (realization access independence IPCAN) IPCAN: IP conncetivity access network Voice over IMS 3GPP Release 7 IMS TISPAN NGN Extensions eCall via IMS ICS Charging and QoS Optimizations
IMS history (cont)
3GPP Release 7 IMS centralized services Charging and QoS Optimizations
3GPP Release 8 Common IMS IMS Extensions for packetized switched streaming MM broadcast/multicast services Session mobility support
3GPP Release 9/10 home node B M2M IMS basic architecture (3GPP 23.002)
Databases Databases Application HSS/SLF AS
MGCF P-CSCF I-CSCF S-CSCF MRF
BGCFMGCF
MGCF IMS Core MGCF
MGCF MGCF MGW SGW
IP Core CS mobile, PSTN IMS basic architecture (cont) IMS & UMTS/ LTE – EPC networks
IMS PSTN AS MGW CSCF
PDN GMSC GGSN HSS GW 3G Core MSC/ SGSN MME Serving VLR GW
RNC
NodeB eNB
UTRAN E-UTRAN IMS & UMTS/ LTE – EPC networks (cont)
EPC Components Mobility Management Entity IMS + Internet Serving Gateway Home Subscriber Server Packet Data Network Gateway PDN HSS Functions GW AAA Mobility Management MME Serving IP over LTE GW QoS, Charging
eNB
E-UTRAN IMS registration & session setup
Public Presence Presence
Internet Databases Converged Converged Services Platforms and
xDSL AAA DHCP
MMS MMS SMS IP Network PDG/PDG HSS DNS SMS
WAG
PDG/PDG Conversational -
WAG -
IMS WiFi PDF S-CSCF I- CSCF PDG/PDG P- CSCF WAG Service Provider
PDN
SSF Data Network
BGCF Streaming
MGCF
PS Backbone
SGSN Network GGSN
CSCF: Call Session Control Function RNC HSS: Home Subscriber Server (includes HLR) MGW: Media Gate Way MGCF: Media Gateway Control Function MGW SGW 3G RAN PDG: Packet Data Gateway PDN: Packet Data Network RAN: Radio Access Network RNC, BSC: Radio Network Controller (3G), Base Station Controller (2G) IMS IP Multimedia Subsystem PSTN BSC SGSN: Serving GPRS Support Node PLMN GGSN: Gateway GPRS Support Node AS (provider, 2G RAN 3rd Party) access network Core network IMS registration
Registration in 2G/ 3G access UE SGSN/GGSN IMS Network (location update) through SGSN/ HLR
1. Bearer Level Registration: GPRS Attach
IP address assignment by GGSN 2. PDP Context Activation (Packet Data Protocol Context)
3. P- CSCF Discovery P-CSCF address determination through GGSN or DHCP server 4. IMS Registration
Request via P-CSCF I-CSCF to Home network. AAA and S-CSCF Assignment by home network IMS registration (cont)
IMSI/ UID
Auth. Info
Adr. S-CSCF
HSS U-Profile core nw
U_Reg Query Adr(SCSCF) (Home) UID
Adr. UE Forward (REGISTER) I-CSCF S-CSCF Adr. PCSCF
OK
UID
access nw Adr. UE Forward (REGISTER) Adr.ICSCF= f(UI) (home, visited) Adr. ICSCF
Adr. SCSCF
Adr. GGSN P-CSCF
OK
IMSI/ UID OK SGSN GGSN PDP Adr. (UE) REGISTER TEID (UI) Adr. PCSCF
Adr. SGSN PSTN voice call
HSS
6 2 3
S_CSCF 4 MGCF
ISUP 5 SIP 1
7 P-CSCF
8 5 8 PSTN/ISDN 5
8 SGSN GGSN MGW TDM
VoIP
1. Incomming PSTN call 3. S-CSCF addree, UID 6. Ressource reservation confirmation 2. Protocol transformation & 4. INVITE Session 7. MGW activation localisation 5. Forward (INVITE) 8. IP PDU transformation & transport IP media session establishment
1. Session initiation (URI HSS callee)
2. 2. HSS request for callee localization (IP domain)
3. CSCF 2 CSCF 1 3. Forward session initiation
4. Caller notification, 4. 1. Bearer establishment 4. 1.
UMTS/ 4. 1. UMTS/ SGSN GGSN GGSN SGSN 5. IP PDU streaming GPRS GPRS 5. 5. 5. 5. 5.
IMS Billing (3GPP 32.240)
OCF charging
account information
IMS GWF charging information online
P-CSCF S-CSCF AS MGCF BGCF
CTF CTF CTF CTF CTF
charging Events
CDF
CDR Billing System charging
CDR CGF offline
CDF Charging Data Function CGF Charging Gateway Function OCF Online Charging Function CTF Charging Trigger Function IMS centralized services (3GPP 23.292)
Enables IMS services when using CS devices (CS access)
Enables CS access to transport IMS voice/video services where PS access is not available for VoIP/ IP-Video (no full duplex speech/video component by PS)
IMS centralized services (cont) Service Centralization and Continuity Application Server (SCC AS): SCC AS is a home network based IMS Application that provides functionality required to enable IMS Centralized Services Acts as ICS User Agent (IUA) and provides SIP UA behavior on behalf of the UE for setup and control of for IMS sessions using CS bearers processes as CAA (CS Access Adaptation) the service control signaling received via the CS access for interworking with other IMS functional elements Directs an incoming session to an ICS User ICS provision in UE Communicates with the SCC AS for service control signaling. Establishes the Bearer Control Signaling Path to setup the media through the CS domain ICS provision in MSC Server: MSC Server processes the user-network signaling received over the CS access for interworking with IMS SIP and vice versa. It controls the MGW functions described to enable the interworking between CS access and RTP bearers. It performs the interworking to support multimedia call in ICS.
Multimedia session continuity (3GPP TR 23.893 )
Media component transfer
Different network access
Different UE
Continuation of ongoing media session
IMS & NGN (ITU-T Y.2021)
Application Platform
IMS
NGN Service Stratum
NGN Transport Stratum
The 3GPP IMS is the central service control component in NGN IMS & NGN (cont)
Applications
Service Stratum Application SupportApplication Functions andFunctions Service Support Functions
Service S. User Other NGN Control Profile Service Components Functions Functions IPTV Service Component
PSTN / ISDN Emulation Other Networks Other Service Component Networks Other IP MultimediaIP Multimedia Component &PSTN/ISDNService Component Simulation GW Legacy Terminals
Network AccessAttachment Resource and Admission
T. UserUser GW ProfileProfile Control Functions Control Functions Legacy Attachment Functions FunctionsFunctions (NACF) (RACF) Terminals
Customer Networks Core Transport Access TransportNetwork Core transport FunctionsFunctions Edge FunctionsFunctions NGN Functions Terminals End- U ser Transport Stratum Functions ETSI TISPAN IMS & NGN (cont)
The 3GPP IMS is the central service control component in NGN
3GPP functional entities NGN functional entities S-CSCF S-CSC-FE
P-CSCF P-CSC-FE
I-CSCF I-CSC-FE
MGCF MGC-FE
MRFC MRC-FE
BGCF BGC-FE Relationship EPC/ NGN-FE’s
Access network Core network ITU-T 3GPP entity Functions performed Y.2018 entity HSS responsible
NAS signalling NACF NAS signalling security NACF hPCRF AS security control NACF Rx S6a Home Gx Inter CN node signalling for mobility between 3GPP NACF S9 access networks SGi Idle mode UE reachability (including control and TBD* PDN Operator's execution of paging retransmission) gateway IP services (IMS, etc.) Tracking area list management (for UE in idle and TBD (Note 1) active mode) S10 PDN GW and serving GW selection TBD (Note 2) Mobility management entity (MME) MME selection for handovers with MME change NACF MME S8 vPCRF S1-MME SGSN selection for handovers to 2G or 3G 3GPP NACF access networks S3 S11 Gxc Roaming NACF (TAA- FE) S1-U Serving E-UTRAN gateway Authentication NACF (TAA- FE) S4 Visited Bearer management functions including dedicated HDC-FE bearer establishment 2G/3G Support for ETWS message transmission NACF SGSN Y2018(09)_FIII.2 The local mobility anchor point for inter-eNB L2HE-FE handover Mobility anchoring for inter-3GPP mobility L2HE-FE E-UTRAN idle mode downlink packet buffering and L2HE-FE initiation of network triggered service request procedure
Lawful interception EN-FE Packet routing and forwarding EN-FE Serving gateway Transport level packet marking in the uplink and the EN-FE downlink Accounting on user and QCI granularity for inter- EN-FE operator charging UL and DL charging per UE, PDN, and QCI EN-FE Originator of PMIP signalling. Proxy point for PMIP MLM-FE(P) signalling (chained PMIP) tunnel end point L3HEF IMS migration scenarios
Not at all
network without IMS
time From the beginning (Greenfield)
IMS based network
time IMS migration scenarios (cont)
Full introduction
network without IMS IMS based network
time Stepwise migration
IMS Introduction together with new broadbad services network without IMS ICS to cover CS
time Summary
IMS has left the trial stage and has become an adequate System to enhance IP sessions in mobile networks with QoS/ security provision and appropriate billing capabilities
IMS enables fix-mobile convergence and is the 3GPP-TISPAN implementation of the service control in the NGN service stratum (e.g. VoIP services via DSL and mobile access)
Large IMS deployment is feasible in the next years based on PSTN migration from CS to IP by big incumbents as well as the deployment of LTE. The IMS benefits and the practical application have been understood and identified by the operators
IMS expectations
Source: Hype Cycle according Gartner Inc. Thank You !