IMS Architecture: Past, Present and
Future
By Dhananjay Shukla and Vinay Rao
Centillium Communications Inc.
IMS Architecture: Past, Present and Future
• Introduction
–
–
–
–
–
–
What is IMS?
Convergence and IMS Drivers
IMS Evolution
IMS Origins
Who is involved?
ITU IMT-2000 Framework
• 3GPP
– About 3GPP
– Standards Releases
– IMS Reference Architecture
• 3GPP2
– About 3GPP2
– Standards Releases
– MMD Architecture
3
IMS Architecture: Past, Present and Future
• 3GPP/3GPP2
– Differences
– Harmonized Architecture
• Evolution from Wireless to Wireline
• NGN TISPAN
– About TISPAN
– Standards
– Architecture
4
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.
5
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
6
FIXED
IMS
BROADBAND
MOBILE
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
IMS Origins
2002
2001
Rel. 4.0
2003
2004
2005
Rel. 5.0
Rel. 6.0
Rel. 7.0
IMS
IMS
IMS
Rel. 0
Rel. A
Rel. B
MMD
MMD
MMD
Rel. 1.0
Rel. 2.0
NGN
NGN
2006
Rel. 1.0
NGN FG
Other
OMA
8
* IP multimedia subsystem (IMS), multimedia domain (MMD), Next Generation Network (NGN)
Who is involved?
9
Standards Organization
or Consortium
Scope or Focus
Standards Contribution
Internet Engineering Task
Force (IETF)
All IP networks
SIP, SDP, RTP,
DIAMETER, etc
Third-Generation
Partnership Project
(3GPP)
UTRA, GSM, GPRS,
EDGE, UMTS, W-CDMA,
etc
IP Multimedia Subsystem
[IMS]
Third-Generation
Partnership Project 2
(3GPP2)
CDMA2000, etc
Multimedia Domain [MMD]
European Telecom
Standards Institute (ETSI)
Next-generation wireline
networks
NGN effort by TISPAN
International
Telecommunication Union
(ITU-T)
IMT-2000 and
Next-generation wireline
networks
Framework for 3G efforts,
FG-NGN effort by
ITU-T SG13 NGN, etc
Open Mobile Alliance
Mobile Services and
Applications
Instant Messaging, OMAPOC, Presence, etc
CableLabs®
Cable IP Networks
PacketCable™ 2.0 project
ITU IMT-2000 Framework
The 5 IMT 2000 terrestrial interfaces agreed by ITU-R
UMTS
Direct
sequence
Time Code
Single
Carrier
Multi-Carrier
Frequency
Time
DS
TC
SC
MC
FT
UTRA FDD
UTRA TDD
High & low
chip rates
UWC 136
CDMA2000
DECT™
TR45
10
3GPP2
3GPP: About 3GPP
• The 3rd Generation Partnership Project (3GPP) Collaboration agreement formalized in December 1998
by signing of “The 3rd Generation Partnership Project
Agreement”.
– Collaboration agreement brings together as “Organizational
Partners”, a number of telecommunications standards bodies
from around the world, namely ETSI (Europe), ARIB/TTC
(Japan), CCSA (China), ATIS (North America) and TTA (South
Korea).
• 3GPP scope is to specify a global (3G) mobile phone
system under ITU's IMT-2000 framework.
• 3GPP specs are based on evolved GSM specs.
• 3GPP standardization encompasses Radio, Core
Network and Service architectures.
11
3GPP: Standards Releases
• Release '99
– functionally frozen December 1999. Defines UTRA and many other initial
features
• The basis for early 3G deployment
• Release 4
– functionally frozen March 2001. 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 2002. 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: 2nd 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)
12
3GPP: IMS Reference Architecture
IP Multimedia Networks
Legacy mobile
signalling Networks
CS Network
Mm
Mb
Mb
CS
BGCF
I-CSCF
AS
Mm
CS
Mk
Mk
ISC
Mw
Mj
Sh
Cx
C, D,
Gc, Gr
BGCF
Mi
Cx
IMMGW
MGCF
Mc
MRFP
MRFC
Mp
Mb
Mb
Mg
Mr
Mb
Mb
HSS
S-CSCF
Dx
SLF
Mw
Dx
P-CSCF
UE
Gm
Ut
IMS Subsystem
3GPP TS 23.228 V7.2.0 (2005-12)
13
IMS Reference Architecture
• IMS reference architecture is based on multi-standard and multiindustry architecture.
• IMS reference architecture is being defined by all major wireless
and wireline standards bodies including, 3GPP, 3GPP2, ETSITISPAN, IETF, WiMAX Forum, OAM and others.
• IMS reference architecture unifies next-generation services
across the user applications, user devices, access networks,
and core network.
• IMS provides an infrastructure for multimedia services such as
telephony, video, multimedia messaging and games – for one-toone or one-to-many multimedia communications.
14
IMS Architecture: Simplified view
• Simplified View – Three Layers
AS
Service Layer
MRF
HSS
CSCF
Control Layer
15
Access Layer
MFCF/
MGC
IP
PSTN/PLMN
IMS Architecture: Session Control Layer
• Session Control Layer
– consists of network control servers for managing calls,
establishing sessions and making modifications.
– two main elements: the call session control function (CSCF)
and the home subscriber server (HSS).
– the call session control function (CSCF) handles end-point
registration and inspect/routing the SIP signaling messages
to the application server. The CSCF is also responsible for
interoperating with the access layers.
16
– the home subscriber server (HSS) maintains the end user’s
service profile. The service profile includes date such as
registration information, roaming and end user’s
preferences.
IMS Architecture: Service Layer
• Service/Application Layer
– provides value-added services using application and content
servers.
– two main elements: the Application Server (AS) and the
Media Resource Function (MRF).
– the application server (AS) is responsible for call flows,
database accesses and user interface interactions.
– the MRF provides the media processing capability for the
application layer. It has two componenets: media resource
function controller (MRFC) and media resource function
processor (MRFP).
– the MRFC is a signaling plane node (SIP user agent to the
S-CSCF) and the MRFP is a media plane node (provides all
media-related functions).
17
3GPP2: About 3GPP2
• The Third Generation Partnership Project 2 (3GPP2)
is a collaboration of North American and Asian
interests also under the framework of ITU’s IMT-2000.
– Collaboration brings together as “Organizational Partners”,
Five Standards Development Organizations, namely, ARIB
(Japan); CCSA (China);TIA (North America); TTA (Korea)
and TTC (Japan) with market representation by CDMA
development group, IPv6 forum, International 450
association.
• 3GPP2 specs are based on evolving ANSI/TIA/EIA41 specs commonly known as CDMA2000
• Four Technical Specifications Groups
–
–
–
–
18
TSG-A (Access Network Interfaces)
TSG-C (cdma2000®)
TSG-S (Services and Systems Aspects)
TSG-X (Core Networks)
3GPP2: MMD Architecture
19
3GPP/3GPP2: Differences
3GPP
• Mandates IPv6
• Special GPRS procedure is
used for Address.
• GGSN and P-CSCF need to
be located in the same
network.
20
• 3GPP uses GPRS packet
services
• Smart cards are mandatory
• 3GPP doesn’t allow HTTP
digest authentication
• IP Multimedia Subsystem
[IMS]
•
•
•
•
•
•
•
3GPP2
Allows both IPv4 and IPv6
DHCP or P-CSCF address on
MS/R-UIM for IP Address.
PDSN and P-CSCF allowed
to be located in different
networks (e.g., PDSN in
visiting network and P-CSCF
in home network.)
3GPP2 uses packet data
service and Mobile IP
Smart Cards are optional
3GPP2 allows HTTP digest
authentication.
Multimedia Domain [MMD]
= IMS + CDMA Packet Data
3GPP/3GPP2: Harmonized Architecture
IP
MULTIMEDIA
SUBSYSTEM
IP
MULTIMEDIA
SUBSYSTEM
P-CSCF
S-CSCF
P-CSCF
S-CSCF
I-CSCF
APP SRV
I-CSCF
APP SRV
3GPP
3GPP2
GPRS Core
Network
Packet Data
Subsystem
SGSN
PDSN
GGSN
MIP HA
CORE NETWORK
RADIO ACCESS NETWORK
(RAN)
3GPP
RAN
21
RNC
NODE-B
3GPP2
RAN
BSC
BTS
Evolution from Wireless to Wireline
22
Source: Cisco Paper - Supporting the IP Multimedia Subsystem for Mobile, Wireline, and Cable Providers.
TISPAN: About TISPAN
• Telecoms and Internet converged Services and
Protocols for Advanced Networks [TISPAN]
• ETSI core competence centre for fixed networks and for
migration from switched circuit networks to packet-based
networks with an architecture that can serve in both.
• Responsible for all aspects of standardisation for present
and future converged networks including the NGN (Next
Generation Network) and including, service aspects,
architectural aspects, protocol aspects, QoS studies,
security related studies, mobility aspects within fixed
networks, using existing and emerging technologies.
23
TISPAN: 3GPP Collaboration
• Building upon the work already done by 3GPP in
creating the SIP-based IMS (IP Multimedia
Subsystem), TISPAN and 3GPP are now working
together to define a harmonized IMS-centric core for
both wireless and wireline networks.
• This harmonized “All IP” network has the potential to
provide a completely new telecom business model for
both fixed and mobile network operators.
• Access independent IMS will be a key enabler for
fixed/mobile convergence, reducing network
installation and maintenance costs, and allowing new
services to be rapidly developed and deployed to
satisfy new market demands.
24
TISPAN: NGN Standards
• NGN Release 1 was launched by TISPAN in December 2005,
providing the robust and open standards that industry can use as
a reliable basis for the development and implementation of the
first generation of NGN systems.
– Terminology, Strategy, QoS, Security, NNA & Identification, ENUM
– Requirements, General architecture, Early services and protocols
– Detailed architecture, Base services/protocols, 3GPP
endorsements
– Operations Support Systems, Congestion control, NGN user data,
PSTN/ISDN emulation
• TISPAN is now working on NGN Release 2 (due sometime this
year), with a focus on enhanced mobility, new services and
content delivery with improved security and network
management.
25
– Content delivery: Streaming, IP-TV, VoD
– Optimized resource usage
– Corporate users specific requirements
TISPAN: NGN Architecture
Applications
Based on
3GPP IMS
IP Connectivity
Access Network
And related functionality
Data
Base
Other Multimedia
Components …
ICF
IP Multimedia
Component (Core IMS)
(SIP-based)
PSTN / ISDN Emulation
(SIP-I based)
“Go”
interface
Legacy
Terminals
Network Attachment
Functionality
NASS
GW
GW
Legacy
Terminals
NGN
Terminals
Customer
Networks
Resource and Admission
Control Functionality
RACS
“Go”
interface
IP
Access Transport
Network
PSTN / ISDN
Legacy
Terminals
Other Networks
Streaming Services
(RTSP-based)
TGW
MBG
Core Transport
Network
NGN
Terminals
3GPP IP-CAN
3GPP Terminals
* Diagram from ETSI TISPAN Ref.
26
TISPAN: New 3G-NGN MGW Function
TISPAN NGN functional architecture Rel. 1.
• Media Gateway Function (MGF)*
– The residential MGF (R-MGF) is located on customer
premises.
– The access MGF (A-MGF) resides on the network operator’s
premises (IP access network or core network).
– The trunking MGF (T-MGF)** resides in the boundary
between an IP core network and the PSTN/ISDN.
* From Rel 1. Doc
** Same as IMS-MGW in 3GPP
27
TISPAN: New 3G-NGN MRFP Function
TISPAN NGN functional architecture Rel. 1.
• Media Resource Function Processor (MRFP)
– Specialized resource processing functions beyond those
available in media gateway functions
– Multimedia conferences
– Multimedia announcements
– IVR capabilities
– Media content analysis
28
IMS Common Platform FMC MGW/MRFP Vision
•
Common HW/SW IMS MGW/MRFP
–
–
–
•
Safeguards future network deployments
Accelerates delivery of real-time
multimedia services
Enables fixed mobile convergence today!
PSTN/
PLMN
MTA
BB Access
Single, all-in-one, common software
–
–
–
–
–
–
PSTN
NGN-VoIP
GSM/W-CDMA/3GPP
CDMA2000/3GPP2
Next-gen session boarder controller
(SBC) with media functions.
Media services
•
•
•
•
29
IP
Announcements/rec
Rich conf.
Rich and programmable tones
Video and other (roadmap)
IMS-MGW
MGF
MGCF
Other
Blocks
MRFP
MRFC
IMS
Bearer
3GPP (WCDMA)
(& TD-SCDMA China)
3GPP2 (CDMA Evolution)
Control
What’s in store?
2005
2007
2006
Rel. 7.0
2008
2009
Rel. 8.0
Rel. 2.0
Rel. 3.0
NGN
NGN
Rel. 2.0
NGN FG
30
* IP multimedia subsystem (IMS), multimedia domain (MMD), Next Generation Network (NGN)
Standard updates in the works -1
• 3GPP
– Rel 7.0 Stage 3 Mid-2007
• IMS Emergency Call handling, eCall, Backup algorithms, etc.
– Rel. 8.0
• Security related updates: Multimedia Priority Service, Voice
Group Call Service [VGCS] enhancements for public safety and
public warning,
• Emergency Calling Data transfer, etc;
• IMS updates for Packet Cable,
• 3GPP2
– IMS Bridge
– IMS/MMD Superstructure
31
Standard updates in the works -2
• ETSI – TISPAN NGN Release 3.0 based on 3GPP
Rel. 7.0
–
–
–
–
Inter-network domain nomadicity
User-controlled roaming
Higher bandwidth access
Fully nomadic (WiMAX, VDSL..)
• ITU NGN FG Release 2.0
32
Glossary of Terms
33
•
•
•
•
•
•
•
•
•
•
•
•
CSCF = Call Session Control Function
P-CSCF = Proxy Call Session Control Function
I-CSCF = Interrogating Call Session Control Function
S-CSCF = Serving Call Session Control Function
GPRS = General Packet Radio Service
GGSN = Gateway GPRS Support Node
SGSN = Serving GPRS Support Node
PDSN = Packet Data Serving Node
MIP HA = Mobile IP Home Agent
RNC = Radio Network Controller
BTS = Base Transceiver Subsystem
BSC = Base Station Controller