3GPP IMS Architecture Overview

D1 - 22/06/2004

3GPP IMS Architecture Overview

June 22nd 2004

Steve TSANG-KWONG-UOrange SA2 delegate

E-mail: [email protected]

D2 - 22/06/2004

Agenda

s Introduction of IMSIntroduction of IMS

s IMS Overview (Rel 5 items)

s IMS Rel 6 Items

s IMS Commonality and Interoperability

s Conclusion

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Introduction of IMS 1/3

s IMS introduced in 3GPP Rel5, and further enhanced in Rel6:QIP Multimedia domain for call control based on SIPQ3GPP specifies features to fullfill operator requirements, e.g.:

–QoS control–Charging–Security–Subscription profiles–Interworking with other networks (CS/PSTN)

s IMS provides building blocks allowing faster integration and deployment of IP multimedia services

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s IMS allows operators to have more control on the service level than with GPRS only:QService level awarenessQCorrelation between the SIP application layer and the transport in PS domainQAccess to services in correlation with a subscription profile (e.g. basic, silver, gold…)QBetter control on the packet resources used

s Releases:QRel 5: frozen since March 2003QRel 6: freezing in Sept 2004QRel 7: Starting. Stage 1 requirements currently being defined.

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User IdsUser profile

security roaming

Inter-WorkingCS/PSTN

QoS policycontrol

BasicCall

Control

Service logicAPIs

SIP

charging


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Agenda

s Introduction of IMS

s IMS Overview (Rel 5 items)IMS Overview (Rel 5 items)

s IMS Rel 6 Items


s Conclusion

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IMS Requirements – SA1

s Stage 0Q TR 22.941 (service examples)

s Stage 1Q TS 22.228 (SA1): Service requirements for the IP Multimedia

Core Network Subsystem

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IMS Architecture – SA2

s Stage 2/Stage 3 - Architecture, main principlesQ Architecture: Call control & Service logic, Interworking entities

(BGCF, MGCF, SGW…), Entities for specific functions (charging, QoS…)

Q Reference Points between entitiesQ Main functions: Call control, Security, QoS, Charging,

Interworking with other networks (CS/PSTN),…

Q TS 23.228: IMS architecture and IMS procedures

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IMS

UTRAN

SGSN GGSNUE

PS Domain

IMS ArchitectureI-CSCF

Go Gi

I-CSCF

P-CSCFS-CSCF

Mw

HSS

Cx

Cx

Other IP/IMS network

Mm

CSCFs are the IMS entities responsible of the call control: there are 3 types of CSCFs depending on their role:•P-CSCF (Proxy CSCF)•S-CSCF (Serving CSCF)•I-CSCF (Interrogating CSCF)

The PS domain provides the IP bearer to access to

the IMS, i.e. a PDP context.

The HSS holds the IMS service profile of the subscribers.

S-CSCF interconnects to external IP networks and other IMS networks.If THIG is used by the operator to hide its internal configuration, the connection to external networks goes through an I-CSCF.

Gi

Traffic Plane

Control Plane

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IMS

UTRAN

SGSN GGSNUE

PS Domain

IMS ArchitectureI-CSCF

Go Gi

I-CSCF

P-CSCFS-CSCF

Mw

HSS

Cx

Cx


Mm

SGWMGCF

BGCF

IMS-MGW

Legacy/PSTN

Mk

Mi

Mg

Mj

MnGi

MRF

Gi

Mr

PDF

Go

GqThose entities are

responsible for interworking

between IMS and CS domain/PSTN

In Release 6, the PDF can be separated from the P-CSCF. Those two entities are then connected through the Gq interface.

The MRF is used for multiparty

call control

Traffic Plane

Control Plane

D11 - 22/06/2004

IMS

IMS Architecture

UTRAN

SGSN GGSNUE

PS Domain

I-CSCF

I-CSCF

P-CSCFS-CSCF

HSS


SGWMGCF

BGCF

IMS-MGW

Legacy/PSTN

MRF

PDF

Traffic Plane

Control Plane

Rf

CCF

CGF

Ga

For offline Charging, CCF and CGF are responsible for collecting charging information from PS

domain and IMS entities.

Gz

D12 - 22/06/2004

IMS

IMS Architecture

UTRAN

SGSN GGSNUE

PS Domain

I-CSCF

I-CSCF

P-CSCFS-CSCF

HSS


SGWMGCF

BGCF

IMS-MGW

Legacy/PSTN

MRF

PDF

Traffic Plane

Control Plane

ISCSCF

ECF Ro

OnlineChargingSystem Gy

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IMS Architecture

Functional architecture for the provision of service in the IMS

S - CSCF S - CSCF

SIP Application Server

SIP Application Server

HSS HSS OSA service

capability server (SCS)

OSA service capability server

(SCS)

IM - SSF IM - SSF

Camel Service Environment

Camel Service Environment

OSA application

server

OSA application

server

ISC

Cx ISC

ISC

CAP

MAP

OSA API

SCIM

AS AS

Sh

Si

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IMS Security issues – SA3s Access Security for IMS

Q TS 33.203 “Access Security for IP-based Services”

s Integrity Protection

s Security of SIP signalling between network nodes :Q Stage 2 TS 33.210 “IP network layer security”.

s User authenticationQ Reuse AKA security mechanisms: IMS-AKA

s Lawful interceptionQ TS 33.108 “Handover interface for Lawful Interception (LI) ”

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IMS Codecs & Transport – SA4

s Default codecs for PS Conversational MM applications QTS 26.235 “Packet switched conversational multimedia applications; Default codecs”QDefines default codecs supported by the UE

s Transport Protocol for PS Conversational MM applications QTS 26.236 “Packet switched conversational multimedia applications; Transport protocols”QDefines transport parameters recommended for conversational services

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IMS Charging – SA5s Two separate charging architectures (Off-Line/On-line)

Q On-line : charging information can affect, in real-time, the service rendered

s Correlation within an application/session/media component

s Charging layersQ Access/Transport Layer - charging of usage of bearer resources (e.g. GPRS access services)

Q IP Multimedia/Session Layer - e.g. voice or video with a certain QoS, time based charging.

Q Application/Content Layer - charging of services provided (e.g. games / info).

s SpecificationsQ Stage 1 - TS 22.115 completed Q Stage 2 - TS 23.815 completed (including pre-paid), TS 23.125 (Flow-Based Charging)

on-going.Q Stage 3 - TS 32.225 "Charging Data Description for IMS“ (Rel 5);

TS 32.260 (Rel 6).Q Other related specifications

Q TS 32.240: "Charging management; Charging principles"

Q TS 32.215: "Charging management; Charging data description for the Packet Switched (PS) domain“

Q IETF Internet-Draft, "Diameter Base Protocol“, IETF Internet-Draft, "Diameter Credit Control Application".

D17 - 22/06/2004

IMS Call control – CN1s Stage 2 – Call model

Q CN1– TS 23.218 on call model: Functional requirements of S-CSCF, HSS (E.g. handling by the S-CSCF of mobile originating requests)

s Stage 3 – Information flows & protocol detailsQ CN1:

– TS 24.228 on information flows– TS 24.229 on protocol details– Enhancements and exceptions to IETF SIP specifications, particularly for registration, authentication and session policy.

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IMS QoS and SBLP – CN3 s Stage 2

QTS 23.107 & 23.207 End-to-End QoS concepts and architecture

s Stage 3QTS 29.207 & TS 29.208 (correlation between SIP layer and transport layer in the

PS domain)

s QoS policy control – QoS authorisationQMechanism to authorise or not a requested session depending on its QoS

characteristics

QDetermines the maximum authorized UMTS QoS in the PDP Context for the media

QIt is based on the parameters describing the media of the requested SIP session

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IMS Subscription data – CN4 s Stage 3

QTS 23.008 (Organization of Subscriber data in the HSS, e.g. IMS user profiles)

QTS 29.228 & TS 29.229 (Cx and Dx interface)

QTS 29.328 (Sh interface)

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Agenda


s IMS Overview (Rel 5 Items)

s IMS Rel 6 ItemsIMS Rel 6 Items


s Conclusion

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IMS Phase 2 – Rel 6

s Main Work Items for IMS Phase 2:Q IMS ConferencingQ IMS MessagingQ IMS Group ManagementQ Additional SIP capabilities (e.g. forking)Q Interworking with non IMS SIP networks (IETF SIP, IPV4)Q Interworking between IMS and CS networksQ Local Services

s Other WIs:Q Interworking and migration scenario for IPv4 based IMSQ QoS improvements (Gq)Q 3GPP enablers for services like PoCQ IMS Commonality and InteroperabilityQ Flow-Based Charging

D22 - 22/06/2004

IMS Phase 2

s IMS MessagingQSupport messaging services in the IMS:

–Immediate messaging: message delivered instantly to user

–Session-based messaging: users has to be connected to a messaging session to be able to exchange messages

s IMS Group ManagementQTo be able to manage group of usersQCan be used for different services such as Presence, Instant Messaging…

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IMS Phase 2

s IMS ConferencingQAllows multyparty callsQMRFC/AS entities

s Additional SIP capabilitiesQSIP Forking added in Release 6

s IMS Local ServicesQRoaming users can access local services in the visited network

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IMS Phase 2

s Interworking between IMS and and non IMS SIP networks:QSIP IETF networkQNetwork using IPv4

s Interworking with SIP IETF networksQIMS makes some options in SIP mandatory, e.g. usage of preconditions which might not be supported by IETF SIP terminals.QTS 29.962 “Interworking between IMS & IP networks”

–CN3 identified the procedures and modifications needed for IMS to be able to interwork with external IP networks

–End-to-End solutions endorsed by SA2 for Release 6

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s Interworking between IMS and CS Q Work moved from release 5 to release 6

–Architecture and basic aspects already available in R5–But BICC/SIP or ISUP/SIP mapping was still missing

s TS 29.163 Interworking between IMS and CS networks

Q This Work is based on the work made in ITU-T SG11 on the BICC/SIP and ISUP/SIP mapping (Q.1912)

IMS Phase 2

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IMS Phase 2

s Interworking with IPv4 networksQIPv6 was specified as the only IP version to be used in IMS (may 2000)

–concerns: UE, P-CSCF, S-CSCF, I-CSCFQMotivations for this decision

–IPv4 addressing shortage–Interworking between IMS clients

QSolutions proposed by IETF:–one solution documented in 23.228 using SIP-ALG and

NAT-PT

D27 - 22/06/2004

IMS Other WIs

s New WI considering Early IPv4 based IMS in Release 6QStarted in September 2003 and to be completed in June 2004QTR 23.981 brings recommendations and guidance for Interworking and migration scenarios with IPv4 based IMS.QCRs to 23.228 and 23.221 has been agreed to include possible usage of IPv4 for early deployments of IMS.

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IMS Other WIs

s 3GPP enablers for services like PoCQRelated to OMA work on PoCQOMA reuses IMS functionalitiesQ3GPP studies enhancements needed to IMS to support PoC

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IMS Other WIs

s Policy control EvolutionQDefinition of the Gq interface: separation of P-CSCF

and PDF

s Extension of Policy Control to non-IMS services.QPDF functionalities can be used by Generic

Application FunctionsQExample: Streaming server

D30 - 22/06/2004

Agenda



s IMS Rel 6 items

s IMS Commonality and InteroperabilityIMS Commonality and Interoperability

s Conclusion

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IMS Commonality and Interoperabilitys Commonality:

QCurrently the 3GPP R’5 IMS system is optimised for the 3GPP UMTS and GSM access networks. However, economies of scale (in terms of hardware, software and application development) should be improved by increasing the commonality of IMS for different “IP-connectivity networks” (including specifically the 3GPP, 3GPP2 and W-LAN IP-connectivity networks)

s Interoperability:QA customer using one (eg the 3GPP) IMS system needs to be able to “phone” (ie make a multimedia call with a speech component) users on another (e.g. 3GPP2) IMS system

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IMS Commonality and Interoperabilitys Use Generic terms not specific to GPRS:

QChanges have been done in Stage 2 and Stage 3 IMS specifications (23.228 and 24.229) to make them access independent. PDP context related aspects has been put in an annex.QTerms used: IP-Connectivity Access Network

s TR 23.864 “Commonality and Interoperability between IMSs”–Defines the boundary points in IMS–Requirements on IP-Connectivity Access Network to support IMS

functionalities (SBLP…)

s For information, TS 23.234 on WLAN interworking–General Interworking with 3GPP Packet network–IMS is one of the targeted services.

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IMS Commonality and Interoperabilitys Boundary Points: entities that performs both IMS and

non IMS fonctionalitiesQHSS (contains subscriber profile for usage of IMS and subscriber profile for access to the IP Connectivity Network)QPDF (used for SBLP)QUE (contains IMS SIP application, IMS specific functions related to the IP connectivity network, and IP Connectivity Network generic functions)

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IMS Commonality and Interoperabilitys Requirements on the IP Connectivity Network for Support

of Service Based Local Policy:QInform the IMS when a resource reservation is requested and is removedQEnforce and revoke resource authorisations coming from the IMSQProvide correlation information for charging for the resources usedQProvide Diffserv Edge Functions and Correlation Information for individual IP-Flows

s Three modes available:QAuthorisation onlyQCharging Correlation onlyQAuthorisation and Charging Correlation (as in R5 IMS)

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IMS Commonality and Interoperabilitys SBLP correlates access resource usage and

application level session instance

s Network control of resource usage

s PEF needed in IP Connectivity Network

s On-going discussionon Relationship betweenSBLP and Flow-BasedCharging in SA2

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IMS Commonality and Interoperabilitys Codecs:

QDefault codecs defined for 3GPP IMS terminals are also recommended for non 3GPP terminals.

s SIP Compression:QMandatory only for cellular access: UTRAN, GERAN, CDMA2000

s WLAN:QThe Packet Data Gateway is identified as the gateway to access IMS

D37 - 22/06/2004

IMS Commonality and Interoperabilitys Aspects not handled in TR 23.864 because of lack of

requirements:QUE, ISIM/USIM aspectsQIP version issues: impact of IPv6 only for IMSQSecurity: Rel5 IMS security mechanisms (AKA), security enhancements needed ?QChargingQUser profile and HSS related concepts

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Agenda



s IMS Rel 6 items


s ConclusionConclusion

D39 - 22/06/2004

Conclusions IMS Releases

QRelease 5 specifies the bases of IMSQRelease 6 is a more complete solution: more service enablers available (Interworking with CS, IP networks…)QRelease 7 is under definition (All IP,…)

s IMS CommonalityQGeneral concepts of what should be supported in the IP-connectivity network

D40 - 22/06/2004

ReferencesTS 23.228 Archi IP Multimedia Subsystem (IMS); Stage 2 S2

TS 33.203 Security Access Security (& integrity protection) for IP-based Services”, Stage 2 S3

TS 33.210 Security Netw. domain sec.; IP network layer security (sec of SIP signalling between network nodes) S3

TS 23.218 Call Control IP Multimedia (IM) session handling; IM call model; Stage 2 N1

TS 24.228 Call Control Signalling flows for the IMS Call Control based on SIP and SDP; Stage 3 N1

TS 24.229 Call Control IP Multimedia Call Control Protocol based on SIP and SDP; Stage 3 N1

TS 26.235 User plane Packet Switched Conversational Multimedia Applications; Default codecs S4

TS 26.236 User plane Packet Switched Conversational Multimedia Applications; Transport protocols S4

TS 29.162 Interworking Interworking between the IM CN subsystem and IP networks N3

TS 29.163 Interworking Interworking between the IM CN subsystem and CS networks N3

TS 23.278 Service Logic CAMEL - IP Multimedia System (IMS) interworking; Stage 2 N2

TS 29.278 Service Logic CAMEL Application Part (CAP) specification for IP Multimedia Subsystems (IMS) N2

TS 29.228 User data & interfaces IP Multimedia (IM) Subsystem Cx and Dx Interfaces; Signalling flows and message contents N4

TS 29.229 User data & interfaces Cx and Dx interfaces (based on Diameter) Protocol details N4

TS 29.328 User data & interfaces IP Multimedia Subsystem (IMS) Sh interface signalling flows and message contents N4

TS 29.329 User data & interfaces Sh interface based on the Diameter protocol N4

TS 22.115 Charging Charging & Billing, Stage 1 S5

TS 23.815 Charging Charging implications of IMS architecture S2/S5

TS 32.225 Charging Charging data description for the IMS - Rel 5 S5

TS 32.260 Charging IMS Charging - Rel 6

Documents

3GPP IMS Architecture Overview