IMS IP multimedia subsystem presentation

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IMS – IP Multimedia Subsystem

Architecture, Protocols and ServicesWaldir R Pires JrSiemens Manaus

2005.06.21

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Contents

IntroductionIMS OverviewIMS Applications/ServicesConclusionReferences

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Introduction

Shift towards an all IP system Reasons

Reduction of costs, creation of new revenue Increased competition and innovation demands Internet coverage Merge of fixed and mobile networks Services today are obsolete

Multimedia services not yet available to the mobile networks – a natural evolution

Common Infrastructure for services

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Stove pipearchitecture horizontal

architecture

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Why IMS?

Involved parties Operators, Users, Content

Providers, Legal Authorities, …

All-IP network Interactive Multimedia QoS guarantee Access transparency,

seamless handover AAA, Billing, Charging

Service Aggregation 3rd party Application Servers Services: No preferential

treatment of voice Voice (VoIP) is just one

service, positioned at same level like any other services

Communication security in IP networks Signaling and Media Access and Core Regulatory requirements

(lawful interception, …)

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Contents


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IMS Definition

The IMS is a standards-based architecture that provides: integrated Internet-based, multimedia, multi-session applications

to mobile users at the same time guaranteeing QoS across different access

network technologies and allowing operators to charge transparently through any medium

used. Defined by 3GPP, 3GPP2 and TISPAN

OMA (service interoperability), IETF (Internet standards)

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IMS Consequences

For users Person2person and

person2content communications in voice, text, pictures and video

Availability anywhere anytime through wireless and fixed networks

Access from different technologies (GSM, cdma2000, WLAN, etc)

For operators Definition of a

horizontal architecture reusability of common

functions in multiple applications (From stovepipe to horizontal services)

Interoperability and roaming

Bearer control, charging and security

Key enabler for fixed-mobile convergence

Secure migration to an all IP architecture

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IMS ArchitectureLegacy Service Control Points

Caller ID, Local number portability and 800 services.

Application ServersIMS ApplicationsOSA – GW (Open Service Access Gateway)

inter-working between SIP and APIs for communication services

It allows applications to access presence and call state information, application registration and resource management

in the network

Non-Telephony Servicesoutside the telephony call model, such as

Instant Messaging, Push To Talk and presence enabled

TAS (Telephony Application Server)back-to-back SIP user agent that maintains

the call stateprovides the basic call processing services including digit analysis, routing, call setup, call waiting, call forwarding, conferencing,

etc.

IM-SSF (IP Multimedia Services Switching Function)

Provides the interworking of the SIP message to the corresponding CAMEL, ANSI-41, INAP

or (TCAP) messages, services such as calling name, 800 services, etc.

HSS (Home Subscriber Services)A database that maintains the unique service profile

for each end user. This includes an end user’s current registration information (i.e., IP address), roaming information, telephony services (i.e., call

forwarding information), instant messaging service information (i.e., buddies list), voice mail box options

(i.e., greetings), etc. CSCF (Call Session Control Function)

It provides the registration of the endpoints and routing of the SIP signaling messages to the

appropriate application server. The CSCF interworks with the transport and endpoint layer to guarantee

QoS across all services. In some IMS proposals, the CSCF is divided into Serving, Proxy and Interrogating

CSCFs.

MRCF – Media Resource Control FunctionIt interworks the SIP signaling with the signaling used by the media servers. It also manages the distribution of sessions

across multiple media servers. It is considered to be the central unit for media processing (transcoding, conferencing, TTS,

etc.),

MGCF – Media Gateway Control FunctionIt interworks the SIP signaling with the signaling used by the

media gateway (i.e., H.248).

Media ServerResponsible for the processing and generation of multimedia

data, such as playing of announcements (audio/video), multimedia conferencing (e.g. mixing of audio), text to speech

conversation (TTS) and speech recognition and realtime transcoding of multimedia data (i.e. conversion between

different formats). Media Gateway

It terminates voice data from a switched network (PSTN) and media (RTP) streams from packet switched network (Internet).

It also acts as relays for multimedia streams i.o. end-2-end connections. Other functions include transcoding, echo

cancellation and packet loss handling

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IMS Architecture

CSCF - Call Session Control Function

Serving CSCFSIP server that maintains

session state for IMS services

Proxy CSCFthe first point of contact for the user entity and forward SIP messages to

the user’s home S-CSCF

Interrogating CSCFthe contact point for a network

when other networks need to be contacted

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IMS Protocols

Session Control SIP

Media RTP and RTCP

Security Diameter (AAA) GSM, GPRS and 3G

standards

IP

UDP TCP

SIP

RSVP RTP RTCP SAP SDP

Multimedia Applications

Audio Video Dados

Used for establishing, modifying and terminating

multimedia sessions. It relies on other protocols for

transport and QoS reservation.

Real Time Protocol: transport of real time media

using UDP

Real Time Control Protocol: control of the real

time media being transported, QoS statistics,

synchronization (audio/video) of packets.

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Contents


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IMS Services/Application Architecture

Architecture Proposals On the operator’s network

Horizontal architecture

On the mobile device

Client-server Three-layer

From the mobile terminal down to the content providers/application developers

Mobile Terminal

Radio Access Network

IMS

SIP Applications

3rd Party Content Providers

Application Developers

Packet Switch Domain Circuit Switch Domain

Internet PSTN

Mobile Terminal

Radio Access Network

IMS

SIP Applications

3rd Party Content Providers

Application Developers

Packet Switch Domain Circuit Switch Domain

Internet PSTN

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IMS Horizontal Architecture

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On the mobile device Client Server Architecture

Mobile terminal and the A/S Three-layer application architecture

User interface, application logic and the protocol layer

Provide maximum portability and flexibility between different vendors = Componentry

Performance problems for multimedia applications in Java

Efficient Java/Native connectivity for multimedia applications

Various application domains

Access IndependencePush-to-talk Over CellularPresenceUnified MessagingInteractive Voice ResponseEnhanced Voice MailInstant MessagingWeb/Audio/Video ConferencingVideo TelephonyMulti-user Gaming

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IMS Summary

IMS provides AAA (authentication, authorization and accounting) of both

mobile and fixed SIP clients Control over sessions

person-to-person, person-to-group and content-to-person multimedia communication

Charging functionality flexibility for the operator apply time-based, event-based or volume-based charging to

subscribers QoS for the IP services being used in the communications

session Functionality to connect roaming users to the home domain for

IP multimedia services Access network domain security functions

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IMS Summary

Enabler to a true 3G IP convergence

Horizontalarchitecture to servicesand applications

Common services and roaming discovery

Interoperability, charging, roaming control for the operator

Combination of voice, video and data

Access convergence GPRS, cdma2000, WLAN, fixed network, etc.

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Conclusion

Issues/Challenges Costs of conversion to IMS Competition and market divergence Performance Security

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Contents


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References

[1] V. Koukoulidis and M. Shah, The IP Multimedia Domain in Wireless Networks: Concepts, Architecture, Protocols and Applications, Siemens Information and Communication Mobile, Boca Raton, Fl, Proceedings of the IEEE Sixth International Symposium on Multimedia Software Engineering (ISMSE’04), IEEE, 2004.

[2] P. Polvora, C. Öström, Plan Your IP-Competence Strategically, Ericsson Seminar, http://www.ericsson.com/learning, April 2005, Ericsson AB 2005.

[3] 3GPP Homepage, http://www.3gpp.org/specs/specs.htm

[4] Open Mobile Alliance (OMA) Homepage, http://www.openmobilealliance.org

[5] Session Initiation Protocol Charter Homepage, http://www.ietf.org/html.charters/sip-charter.html

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References

[6] IP Multimedia Subsystem (IMS): Service Architecture, Lucent Technologies, February, 2005,

[7] IMS – IP Multimedia Subsystem: The value of using the IMS architecture, White Paper, Ericsson, October 2004,

[8] Motorola IP Multimedia System White Paper, February, 2004,

[9] IP Multimedia: a New Era in Communications, Nokia White Paper,

[10] The Protocol Dictionary Homepage, http://www.javvin.com/protocolH245.html

[11] P. Howard, 3GPP Security and Authentication, September 13, 2001, http://www.ietf.org/proceedings/01aug/slides/sipping-7/index.htm

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References

[12] Open IMS Homepage, http://www.fokus.gmd.de/bereichsseiten/testbeds/ims_playground/playground/hss.php?lang=de

[13] 3GPP TS 23.228: "IP Multimedia Subsystem (IMS)"

[14] IETF RFC 3261: "SIP: Session Initiation Protocol"

[15] 3GPP TS 23.218: "IP Multimedia (IM) session handling, IM call model"

[16] 3GPP TS 29.228:" IP Multimedia (IM) Subsystem Cx Interface; Signalling flows and message contents"

[17] The Parlay Group homepage, http://www.parlay.org/

[18] H. Montes, G Gomez, H Cuny, Nokia Networks, J. Paris, Deployment of IP Multimedia Streaming Services in Third Generation Mobile Networks, IEEE Wireless Communications, October 2002

[19] Siemens IP Multimedia Subsystem (IMS): The Domain for Services, Whitepaper

IMS IP multimedia subsystem presentation

Technology

real time media

ip multimedia subsystem

ip multimedia

multimedia data

telephony services

media gateway

multimedia applications

sip signaling