International Telecommunication Union
ITU-T
Functional Architecture Model
of NGN
Naotaka MORITA
Senior Research Engineer, Supervisor
NTT Service Integration Labs.
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
Definition & Features of NGN
ITU-T
Definition
of NGN
(Rec.
Y.2001)
A NGN is a packet-based network able to provide telecommunication
services and able to make use of multiple broadband,
QoS-enabled transport technologies and in which service-related
functions are independent from underlying transport-related technologies.
It enables unfettered access for users to networks and
to competing service providers and/or services of their choice.
It supports generalized mobility which will allow consistent and
ubiquitous provision of services to users.
Target Standards Area
Generalized Mobility
Convergence btw. Fixed & Mobile
Unrestricted Access
Open Access I/F
Separation Services with Transport
Architecture and Open API
QoS-enabled Transport
Multiple-Broadband
Manageable Broadband
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
2
Characteristics of Next Generation Networks (NGN)
ITU-T
Service-related functions and transport functions are separated into two strata
• Transport functions assume packet-based integrated networks
— The currently widely used IP protocol is the core protocol.
• Service-related functions refer to basic and additional telephone connection functions and the
provision of functions inherent to services such as WWW and video distribution
— Initial studies focused on session control functions for the implementation of IP telephony,
video chat, and video-conferencing using the SIP protocol as the core protocol.
• The NGN separation model supports new independently developed technologies
and flexible system deployment and permits the formation of various
businesses
Video Services (TV, movies, etc.)
Data Services (WWW, e-mail, etc.)
(Any/All Applications
e.g., voice, data, video)
Telephone Services
NGN Service-Related Functions
Anything and Everything
Internet Protocol
(IP)
Everything
Scope
of the
Internet
“Service Stratum”
NGN Transport Functions
(Any and All Network Technologies)
“Transport Stratum”
ITU-T Workshop
onGeneral
“Next principles
Generation
Networks“
Reference: ITU-T Recommendation
Y.2011 —
and general
reference model for next generation networks
Hanoi, Vietnam, 15-16 May 2006
3
Y.NGN-FRA Figure 1. NGN architecture overview
ITU-T
Applications
ANI
Management Functions
Application Support Functions & Service Support Functions
Service Control
Functions
Service User
Profiles
Service stratum
Network Attachment
Control Functions
End-User
Functions
Transport User
Profiles
Resource and
Admission
Control Functions
Transport Control Functions
Other
Networks
Transport Functions
UNI
NNI
Transport stratum
Control
Media
Management
Note: UNI/NNI/ANI
are not meant to represent any specific interfaces.
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
(This type of note is written
in TR-FRA word file.)
4
What is IMS?
ITU-T
IMS
IMSis
isaasubsystem
subsystemproviding
providingcall
callprocessing
processingand
andaavariety
varietyof
ofmultimedia
multimedia
services
servicesin
inan
anIP-based
IP-basedpacket-switching
packet-switchingdomain.
domain.
—
—Provides
Providesvoice,
voice,video,
video,presence,
presence,messaging,
messaging,conferencing,
conferencing,and
andother
other
services
services
—
—Complies
Complieswith
withIETF
IETFstandardized
standardizedsession
sessioncontrol
control(SIP);
(SIP);profiling
profiling
—
—Independent
Independentof
ofthe
theaccess
accessnetwork
network
—
—The
Theapplication
applicationservice
serviceplatform
platformitself
itselfis
isoutside
outsidethe
thescope
scopeof
ofIMS
IMS
Application Service Platform
Other IP/IMS
Networks
IMS
Legacy/
PSTN
IP Transport Network (IP-CAN)
IP-CAN: IP Connectivity Access Network
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
5
NGNs Based on IMS (from Y.IFN)
• Architecture centers on SIP proxy-equivalent Call Session Control Functions (CSCFs).
ITU-T
• Employs a separation model that decouples media processing elements and their controlling
elements.
• Links to transmission systems through a Gq interface.
Rf/Ro
Ut
Charging
Functions
AS
Sh
Dh
SUP-FE
SAA-FE
ISC/Ma
Dx
Cx
Network
Attachement
Control
Function
NSIW-FE
Ib
Mw
Mx
I/S-CSCF
« Core IMS»
Mi
IBC-FE Ic
Mx
Mk
Mw
Gq'
Mj
P-CSCF
Mx
Mg
MRFC
MGCF
SG-FE
Ie
Mp
Mn
PSTN/ISDN
Gq'
Other IP Networks
BGCF
Mr
e2
Gm
Iw
Rf/Ro
SL-FE
AS:
BGCF:
CSCF:
HSS:
IP-CAN:
ISC:
MGCF:
MGW:
MRFC:
MRFP:
P-CSCF:
SLF:
Application Server
Breakout Gateway Control Function
Serving CSCF
Home Subscriber Server
IP-Connectivity Access Network
IMS Service Control Interface
Media Gateway Control Function
Media Gateway
Multimedia Resource Function Controller
Multimedia Resource Function Processor
Proxy CSCF
Subscription Locator Function
Resource and Admission Control Function
MRP-FE
TMG-FE
UE
IP Transport (Access and Core)
IBG-FE
Draft Recommendation Y-IFN: IMS for NGN
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
6
Roaming Implementation with Proxy CSCF
ITU-T
• In IMS nomenclature, the SIP proxy function is called the Call Session Control Function
(CSCF).
• IMS defines a mobile-destination (roaming-destination) SIP server (proxy CSCF) in addition
to the subscribing SIP server (serving CSCF) to allow authentication and QoS control by the
mobile-destination network.
• IMS presumes that the serving CSCF cannot be accessed directly (a walled garden).
B’s Home Network
(New York)
A’s Home Network
(London)
Serving
Serving
CSCF
CSCF
HSS-1
HSS-2
Serving
Serving
CSCF
CSCF
A’s Present Location
(Hong Kong)
Control signal
Voice, images,
or other media
B’s Present
Location
(Tokyo)
Proxy
Proxy
Proxy
CSCF
CSCF
Proxy
CSCF
CSCF
B
A
IP Backbone
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
7
Dynamic Assignment of SIP Proxies with Interrogating
CSCF
ITU-T
• In IMS, a CSCF is assigned to a user each time the user is registered (at power up). (This
accounts for CSCF expansion, loading distribution, and risk distribution.)
• SIP signals from another network are first sent to the interrogating CSCF and then forwarded
to the assigned CSCF.
• The interrogating CSCF has a topology hiding inter-network gateway function that can be
deployed on the exit side as well.
• Fixed-network NGN discussions are permitting the deployment of a border gateway control
function, which is different type of SIP proxy from an interrogating CSCF.
HSS
I-CSCF: Interrogating CSCF
HSS
HSS
Serving
Serving
CSCF
CSCF
Assignment Function
Topology Hiding
Assignment
Function
Serving
(SLF)
Serving
(SLF)
By Encryption
CSCF
CSCF
Serving
Interrogating
Serving
Interrogating
CSCF
CSCF
CSCF
CSCF
Interrogating
Serving
Interrogating
Serving
CSCF
CSCF
CSCF
CSCF
Border
BorderGateway
Gateway
Control
Function
Control Function Topology Hiding By
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
Message Modification
8
IMS and Applications
ITU-T
• Implementation of new service functions
(Examples: call-waiting, conferencing calls, ring-back music, IP centrex, calendar coordination)
• Three types of application servers that connect to SIP servers (S-CSCF):
— OSA (Open Service Architecture Server)
— SIP (SIP Application Server)
— CAMEL (Camel Service Environment)
• Additional studies are looking at the construction of a Service Delivery Platform (SDP) in the
application layer
SDP (Service Delivery Platform)
Application
Layer
Web-type Communication-type
IN-type
APL
APL
APL
Camel
OSA AS
SIP AS
Service
Environment
APL of
ASP
AS for
third
parties
Separate Network
Service
Control
Layer
IMS
HSS
SIP Server
(S-CSCF)
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
9
Y.NGN-FRA Figure 7. Application/Service support
functions
ITU-T
Applications
Application Support
Functions and Service
Support Functions
ANI
A-1: AS-FE*
A-2: APL-GWFE*
A-U1
A-4: SS-FE
A-3: APL-SCMFE*
A-S1 A-S2 A-S3
A-S5
S-6: SAA-FE
UNI
S-15: MLT-FE
End User
Functions
S-1: S-CSCFE
S-13: MRC-FE
A-S6
A-T1
S-5: SUP-FE
S-4: SL-FE
Transport
Processing
Functions
T-9: SG-FE
Service
Control
Functions
S-14: MRB-FE
A-S4
Note: * may include Authentication, Authorization, and Accounting
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
10
*
Application Support Functions & Service Support Functions
(may include own Authentication, Authorization and Accounting)
Service control
S-4:
Subscription
Locator FE
Legacy
Terminal
RGW
Custome
r
Network
Legacy
Terminal
T-13: T. Location
management FE
S-10: Breakout
Gateway Control
FE
S-9: Media
GW
Control FE
T-16: Policy Decision FE
Other NGN
other IP MM
Network
(e.g. IMS)
T-16: Policy Decision FE
T-17: Transport
Resource Control FE
T-17: Transport
Resource Control FE
T-10:
Network Access
Configuration FE
Core transport
T-8:
Media
Resource
Processing
FE
Access transport
T-4: Access
Relay FE
T-1: Access
Media
Gateway
FE
S-12: Network
Signaling
Interworking FE
S-7:
Interconnection
Border Gateway
Control FE
RACF
T-14: Access Management FE
T-2: Access
Node FE
NGN
Terminal
S-13: Media
Resource
Control FE
RACF
T-15: Home GateWay
Configuration FE
T-11:
T. Authentication
&Authorization
FE
S-1: Serving Call Session Control FE
S-8: Access GW
Control FE
NACF
EndUser
Function
S-3: Interrogating Call
Session Control FE
S15:Multimedia
Service FE
S-2: Proxy Call Session
Control FE
T-12: T.
User Profile
FE
S-6: S.
Authentication &
Authorization FE
S-14: Media
Resource Broker
FE
S-5: S. User
Profile FE
S-11: User Signaling
Interworking FE
NGN
UNI
ANI
Application
ITU-T
Management functions
Applications
T-3: Edge
Node FE
T-5:
Access
Border
Gateway
FE
Access Packet Transport Functions
Core Packet Transport Functions
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
Scope of NGN
T-9:
Signallin
g
Gateway
FE
T-6:
Interconnection
Border
Gateway FE
T-7:
Trunk
Media
Gatew
ay
FE
PSTN/ISDN
11
ITU-T
Y.NGN-FRA Figure 8 - Transport and service configuration of
the NGN
Applications
Service Stratum
Application Support
Functions Functions
and Service Support Functions
Application
Service
S. User
Profile
Functions
IP Multimedia
Component
IP Multimedia
&PSTN/ISDN Simulation
Legacy
Terminals
Legacy
Terminals
Customer
Networks
NGN
Terminals
End-User
Functions
Service Component
GW
GW
Network Access
T.User
User Network Attachment
Control Functions
ProfileAttachment
Profile
Functions
(NACF)
Functions
Functions
Access
Network
Access Transport
Functions
Functions
Edge
Functions
Resource and Admission
Control Functions
(RACF)
Other Networks
Other Multimedia Service
Control
Components …
Functions
Streaming Service
Component
PSTN / ISDN Emulation
Service Component
Coretransport
Transport
Core
Functions
Functions
Transport Stratum
* Note: Gateway (GW) may exist in either Transport
ITU-T Workshop on “Next Generation Networks“
Stratum
or End-User
Functions.
Hanoi,
Vietnam,
15-16 May
2006
12
Y.NGN-FRA Appendix I Figure I.5: NGN example of
service domains
ITU-T
Internet
Services
2
Operator A
3
1
Laptop
IP Connectivity
Access Network
IMS
Services
Core Transport
Network
Internet
Services
Internet
Non-SIP
Services
Operator B
Core Network
Access
Network
1 ： IMS services
2 ： Non SIP service
3 ： Internet service
Core Network
Firewall
Transit
Network
Transit
Network
IMS
Services
Core Transport
Network
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
Access
Network
IP Connectivity
Access Network
13
Y.NGN-FRA Figure 2: Charging and Billing Functions
ITU-T
Billing Domain and Backend
Systems
Account
Management
Function
Charging
Collection
Function
Rating
Function
Online
Charging
Function
Charging
Trigger
Function
Offline Charging
Online Charging
NGN
Functional Entity
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
14
Y.NGN-FRA Appendix II Figure II.1 – Multi-Layered Transport
Stratum
ITU-T
Service
Layer
Application protocols (e.g. SIP)
App
App
AAA
Transport IP-C
Layer
IP-B
Mobile IP (using co
- located CoA)
AAA
IPSEC tunnel
AAA
IP-A
IP-C
IP-C
IP
IP-A
IP-B
IP-B
IP-A
IP
Network-C
Host-2
WLAN
Host-1
Node-1
IP
WLAN AccessNetwork-A
Controller
Node-3
Node-2
IP
IPSEC GW Network-B Home Agent
Legend:
Nodes connected with a long
- dashed line (red) are adjacent at the application layer
(e.g. client/server or peer-to- peer application entities)
Nodes connected with a solid line (blue) are Layer
-3 adjacent
Nodes connected with a short
- dashed line (black) are Layer
-2 adjacent
Solid arrow (green) indicates AAA & DHCP flows
Represents a routed IP network
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
15
Y.NGN-FRA Appendix III Figure III.1: Locations of
S/BC functions
ITU-T
Application
Provider
Network
Logical
CCSP MP
Interfaces
Service
Provider C
Logical
Interfaces
CCSP MP
CCSP MP
CCSP MP
Logical
Interfaces
CCSP
Service
Provider
A
MP
CCSP
CCSP
Service
Provider
B
MP
MP
CCSP MP
Enterprise
CCSP Network
Or
Access CCSP
Network
Or
MP
Transit
MP Network
CCSP
MP
Enterprise
Or Home Network
CCSP MP
CCSP MP
Logical
Interfaces
CCSP MP
CCSP MP
CCSP MP
Enterprise
Or Home Network
Application
Provider Network
CCSP: Call Control Signalling Path
MP: Media Path
ITU-T Workshop on “Next Generation Networks“
Hanoi, Vietnam, 15-16 May 2006
16