International Telecommunication Union
ITU-T
IMS based NGN
Architecture
and its application
Dick Knight
BT Group plc
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
Outline
ITU-T
o
IP Multimedia Subsystem
• Overview & Key Features
• Use in NGN
• Benefits
o
Support for PSTN/ISDN Replacement
• Simulation
• Emulation
o
Overall Architecture
• ITU-T SG13, ETSI TISPAN & BT 21CN
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
2
IP Multimedia Subsystem
ITU-T
o SIP-based control system to enable media-
agnostic service delivery in IP networks
• Secure registration
• Secure communications
• Location independence
• Separation from Service providing application
• Specified by 3GPP
o Control system for a flexible service delivery
platform
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
3
Key Elements
ITU-T
HSS
UE
P-CSCF
AS
S-CSCF
NACF & RACF
Transport Network
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
4
Key Elements Functionality 1
ITU-T
o UE – User Equipment
o P-CSCF
• Proxy Call Session
Control Function
• First contact point
• Forward SIP messages
from UE to S-CSCF and
vice-versa
• Generation of CDRs.
• Maintain security
association to UE
• Authorisation of
bearer resources
o HSS Home Subscriber
Server
• Mobility Management
• User security
• Service Provisioning &
authorisation support
• Call / Session
establishment support
• GUP Data Repository
• Identification handling
• Access authorisation
• Application Services
Support
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
5
Key Elements Functionality 2
ITU-T
o S-CSCF
• Serving Call Session
Control Function
• Control for registered
UE sessions
• May behave as Proxy
Server or User Agent
• Interaction with
Services Platforms
• Provide endpoints
with service event
related information
• Obtain Address of
entry point for
network serving the
destination user
• Modify the SIP request
according to HSS and
service control
interactions
• Perform preference
and capability
matching
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
6
IMS in NGN
ITU-T
o Performs Service Control Functions
• Within the service stratum
• Meets the requirements of Y.2001
o Flexible approach to services
• Service delivery using Internet applications,
services and protocols
o Provides inherent mobility support
o Already exists!
o BUT – specific to IP Connectivity Access
networks
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
7
IMS Adaptations in NGN
ITU-T
Specific adaptations to NGN – generic access
IMS
UE
NACF
RACF
Transport Network
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
8
IMS Adapted to NGN
ITU-T
o Control of IP Transport Networks (admission
o
o
o
o
control, QoS, authentication, etc.)
Co-ordination of multiple control
components to a single core transport
Interworking and interoperability with
legacy and other networks
Mutual de-coupling of applications from
session/call control and transport
Access technology independence of
session/call control and applications
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
9
Architecture of IMS for NGN
ITU-T
Figure 1 of draft ITU-T Recommendation Y.IFA
AS
Other IP Multimedia Networks
PSTN
BGCF
MGW
PSTN
Sh
ISC
Mm
HSS
(AAA+DB)
CSCF
Mk
Mj
BGCF
Mn
Cx
Mw
Dh
Mi
Mg
Mb
Mb
MGCF
MRFP
Dx
Mr
Mb
Mp
MRCF
Mw
P-CSCF
Gq
Mb
IP Connectivity Access Network
SLF
CSCF
Gm
UE
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
10
PSTN/ISDN Replacement
ITU-T
o
o
o
o
Simulation
Interactions between
AS and UE provide
“PSTN/ISDN-like”
services to NGN Users
IP “Terminals”
Includes terminal
adapters
Network and UE based
services
o Example use of IMS
Emulation
o PSTN/ISDN service
capabilities and
interfaces using
adaptation to an IP
infrastructure
o Legacy user equipment
and interfaces
unchanged
o Two approaches:
• Call Server
(Softswitch)
• IMS-based
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
11
IMS-Based Emulation
ITU-T
HSS
H.248
PSTN
ISDN
UE
Access
Media
G/W
AGCF
AS
(ISUP-aware)
S-CSCF
NACF & RACF
Transport Network
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
12
Advantages of IMS PES
ITU-T
o
o
o
o
Preserves common interface to RACS &
transport network
Common service control functions
Common Routing and configuration data
between emulated PSTN/ISDN Users and
NGN Users
Economy of scale
•
•
Consider effects of reducing numbers of
emulated users
Provision of advanced services
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
13
Service Control Architecture
ITU-T
Applications
Application
ANI
Based on
Y.FRA Fig. 3
Application
Support
Functions
& Service
Functions
Application
Support
Functions
Service
Support
& Support
Functions
(may include own Authentication, Authorization and Accounting)
User
User Profile
Media Res. Broker
Subscription
Subscription
Locator
Network Sig.
Interworking
I-CSCF
I/C Border
G/W Control
Multimedia
Service FE
P-CSCF
User
Signalling I/W
Authentication
& authorisation
Access
Gateway
Function
Breakout
G/W Control
S-CSCF
Media G/W
Control
Media Resource
Control
Other NGN
other IP MM
Network
(e.g. IMS)
Internet
NGN UNI
End-User
Functions
NACF
Access Packet
Transport Functions
RACF
Core Packet Transport
Function
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
PSTN/ISDN
14
ETSI TISPAN Architecture
ITU-T
(* apart from IMS-based PSTN Emulation)
Rf/Ro
Ut
Rf/Ro
Application Servers
Ut
Sh
UPSF
Rf/Ro
ISC
Dh
Cx
Dx
IMS /
Mw
PSTN
I/S-CSCF
Simulation
PSTN
Emulation (R2)
AGCF
SLF
P3
Mw/Mk/Mm
Mk
Mj
Mg
MRFC
Gq'
MGCF
Ie
SGF
Network
Attachment
Subsystem
Gm
SPDF Resource &
e4
MG
Re
Mp
Mn
Admission
Control
A-RACF
Ia
MRFP
SPDF
RACS
T-MGF
I-BGF
UE
RCEF
CNG
Gq'
PSTN/ISDN
P1
Gq'
Ic
Other IP Networks
Mr
P-CSCF
Iw
Mk
BGCF
Mw
Ib
IWF
IBCF
Mi
P2
e2
Charging
Functions
BGF
IP Transport (Access and Core)
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
15
BT 21CN Architecture
ITU-T
AE
SIP Application
Servers
Service Assembly
CAC
BWM
AGC
F
HSS
plus
ISC
ISC
Mw
P2
I-CSCF
M
S
A
N
e1
e2
Mw
Gq’
SPDF
Ia
Re
MSAN and Access
BRAS
Messaging
BCF
Mw
P- CSCF
Rq
IMS
S-CSCF
Other
IMS
SPDF
Mr
MRFC
Mp
Mg
MGCF
SGF
C7
Mn
Media
Server
PSTN
Backhaul
Presence
SCIM
Cx
A-RACF
SIP
OSA SCS
SIP Stack
Gm
H248
External
Application
s
OSA AS
OSA AS
Sh
e4
POTs
IAD
AS AS AS
Call
Application
Servers
SBR
(ENUM)
PSTN
Call Server
SIP Application Server
3rd Party
Applications
& Services
Border
Gateway
WiMax/WLAN
MPLS/IP
Network
Metro and Core
Media
Gateway
Other TDM
Networks
Border
Gateway
Other IP
Networks
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006
16
International Telecommunication Union
ITU-T
Thank You
ITU-T Workshop “NGN and its Transport Networks“
Kobe, 20-21 April 2006