Transcript Slide 1

IP Multimedia Subsystem (IMS)
Emergency Services
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Christian Militeau
Director, IEN Services Development
ESIF 16 - January 2006
Objectives
Highlight Current Standards Activity
Present an Overview of IMS Architecture
Define IMS Core Network Elements
Illustrate Registration and Call Flow
Present an Overview of IMS in the context of
Emergency Services
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Where does IMS come from?
In Wireline there has been a long term move towards a Voice
over Packet (VoIP) replacement for the PSTN
Drivers have always been to reduce OPEX in fixed line
networks by optimising bandwidth usage, and replacing
outdated TDM switching fabric
– Compressed speech into less than 64kbps channels (G Standards)
– Further optimisation using VAD, Silence Suppression, ATM AAL2 or IP
multiplexing yields significant reduction in core network bandwidth
requirements.
Drivers in 3GPP for Wireless are more service related
– IMS is born out of a need for ‘feature rich’ services
– Bandwidth requirements and their impact on capacity for the Radio interface
(GSM, GPRS, 3G).
IMS provides the final piece in the business case for the NGN
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IMS-Related Standards Initiatives
4
IMS Releases
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What is IMS?
An Industry Standard Service
Architecture (SA) and Core
Network (CN) architecture
Web Portal
Service Architecture
Applications/Services
Plane
Core Network
Session
Control Plane
Application
Servers
Session
Control
An IP Multimedia Services
Architecture
Defined with Open Standards
from 3GPP and ETSI
Centralized
Databases
Based on IETF Protocols
(SIP, RTP, RTSP, COPS,
DIAMETER, etc.)
HSS
CSCF
Access
Network
Media
Server
Media
Control &
Gateways
Access & Transport
Plane
CSCF – Call Session Control Function
HSS – Home Subscriber Server
Other
Networks
Designed for both Wireless
and Wireline Networks and
for Fixed and Mobile
Convergence (FMC)
A Solution for Service
Transparency
Capable of Interworking with
PSTN (i.e. legacy IN-based
services)
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IP Multimedia Subsystem (IMS) - Key Attributes
Open Industry Standard
Support for a Variety of
Applications:
Application
Layer
Common OAM&P Environment
• Ease integration into OSS/BSS/NMS
Web Portal
• Speed Applications to market
Common Session Control Element
to Provide Service Interworking
Application
Servers
Common
OAM&P,Billing,
etc.
Common Subscriber
Database with Open
Interfaces
• Predictable interactions between multiple
services
Session
Control
Layer
Session
Control
Centralized
Databases
Distributed Session Control
• IMS flexibility and scalability reduce OPEX
• Support mobility/portability
Access
Layer
Access
Network
Media
Server
Media
Control &
Gateways
Service Consistency Across Wireless,
Wireline and VoIP Endpoints:
• Retain ownership of the subscriber and their
services
Common support for
CoS, QoS, security,
scalability, reliability, and
performance
Other
Networks
Capable of
Interworking with the
PSTN (i.e. legacy INbased services)
• Ability to provide differentiated services
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IMS Access Network Independence
SIP Application
Servers
DSL/Cable Modem
HSS
SIP Application
Servers
IMS
CDMA 2000
I-CSCF
MRF
DSLAM/CMTS
P-CSCF
MGCF
S-CSCF
MGW
WLAN
MSC(Server)
RNC
SGSN
GGSN
BSC
UMTS/GPRS
Corporate
CN
MGW
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Applications
IMS Converged Communications Services Vision
Session
Control
Presence
Servers
Telephony
Servers
Unified
Messaging
HSS
Service Broker
Pres.
Data
MRFC
Transport
CSCF
Loc.
Data
Group
Lists
Access
Micro Billing
Integrated
Pre-paid &
Postpaid
AAA
Media GW
Signaling GW
PSTN
IP LAN
DSL/Cable
WiFi/802.11x
Office/Hotel
Home
Hotspot
Wireless
Router
IP-PBX
Devices
Subs
Data
Managed Core IP Network
Media
Server
GGSN
PDSN
Cellular
MSC
On the Road
SS7
5ESS
Local Loop
Home/Office
Base
Station
Access
Point
Ckt-PBX
IP-phones
(IP-Centrex)
IP-phones
Clients
Network Operations, Applications
Mgt, Subscriber registration/
authorization
Soft-phones
Dual-mode
WiFi phone
VoIP
handset
Ckt
handset
POTS
phone
ISDN-phones
Multiple user interfaces with common look and feel
SIP Clients
Other Clients
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IMS Functional Elements
Session Management (SIP)
Routing
Databases
Network Interoperability Elements
Services and Support Components
Charging Components
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IMS Functional Elements
Application Server (AS)
Breakout Gateway Control Function (BGCF)
Call Session Control Function (CSCF)
Home Subscriber Server (HSS)
Media Gateway Function (MGW)
Media Gateway Control Function (MGCF)
Multimedia Resource Function Controller (MRFC)
Multimedia Resource Function Processor (MRFP)
Security Gateway (SEG)
Serving/Gateway GPRS Support Node (SGSN/GGSN)
Signaling Gateway (SGW)
Subscription Locator Function (SLF)
Service Capability Interaction Manager (SCIM)
Policy Decision Function (PDF) – “Bandwidth Manager” (CoS & QoS)
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IMS Home Network - Functional Elements
Home Subscriber Server
Domain Name Server
• Centralized DB
• HLR successor
• User profile
• Filter criteria (sent to S-CSCF)
• Which applications
• Which conditions
Application Servers
• Push-to-talk
• Instant messaging
• Telephony AS
• 3rd party or IMS Vendor
Media Resource Function Controller
• Pooling of Media servers (e.g. conference)
Home Network
DNS
ENUM
AS
AS
AS
HSS
P-CSCF
Media Gateway
Control Function
Diameter
SIP
P-CSCF
UA/UE
I-CSCF
SIP
S-CSCF
SIP
SIP
MRFC
MS
SIP
SIP
UA/UE
SIP
MS
• Interfaces to PSTN/PLMN by
• Converting SIP <-> ISUP
• Interworking RTP to circuit
• H.248 control of MGW
SIP
BGCF
SIP
MGCF
ISUP
SIP
Call Session
Control Function
• SIP registration
• SIP session setup
RTP
MGW
SS7
TDM
PSTN
Serving CSCF
Proxy CSCF
•
contact point for UA
• QoS
• Routes to S-CSCF
1st
H.248
Visited
Network
• Registrar
• Session control
• Application Interface
Interrogating CSCF
• Entry point for incoming calls
• Determines S-CSCF for Subscribers
• Hides network topology
Breakout Gateway Control Function
• Selects network (MGCF or other BGCF)
in which PSTN/ PLMN breakout is to occur
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IMS Network-to-Network Connectivity
SIP
UA/UE
Access
DNS
ENUM
RTP
RTP
Visited
Network
HSS
Diameter
SIP
Backbone
Packet
Network
AS
AS
AS
SIP
P/S-CSCF
SIP
I-CSCF
SIP
S-CSCF
P-CSCF
SIP
SIP
SIP
MRFC
MS
SIP
SIP
MS
SIP
BGCF
SIP
MGCF
ISUP
RTP
Home
Network
H.248
MGW
SS7
TDM
PSTN
Proxy/Serving CSCF
•Manages call origination
•Selects destination network
• Routes to I-CSCF
Interrogating CSCF
• Entry point for incoming calls
• Determines S-CSCF for Subscribers
• Hides network topology
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IMS UE Registration
Register
MAR/MAA
Register
Unauth
HSS
MAR/MAA
S-CSCF
Register
Unauth
P-CSCF
Register
UA/UE
•The UA/UE Registers with the S-CSCF
•The S-CSCF consults HSS for Authentication
•The S-CSCF Challenges the UA/UE
•The UA/UE Registers with Credentials to the S-CSCF
•S-CSCF Authenticates with HSS and Downloads User Profile
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IMS Subscription to UE State Changes
Subscribe
Notify
HSS
S-CSCF
Subscribe
Notify
P-CSCF
Subscribe
Notify
UA/UE
• The P-CSCF Subscribes to the UA/UE Registration State
• S-CSCF Notifies the P-CSCF of Registration State
• The UA/UE Subscribes to its Registration State
• S-CSCF Notifies the UA/UE of Registration State
Now the Elements can Inform Each Other of Registration State Changes
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A Typical Example of an IMS Call
Network Y
Network X
AS
AS
S-CSCF
S-CSCF
HSS
HSS
I-CSCF
I-CSCF
P-CSCF
P-CSCF
SGSN
DSL/Cable Modem
GRX
Network Z (UMTS/GPRS)
GGSN
DSLAM/CMTS
RNC
User A
User B
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IMS (3G) Emergency Services Architecture
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3GPP IMS R7 Emergency Sessions
Connectivity to Network
Capable of Delivering
Call to IP PSAP
• 3GPP View of Emergency Sessions
IP Access Network
Initiates Emergency
Call
IMS Core Network
IP Connectivity
Access Network (ICAN)
DNS
ENUM
AS
AS
AS
HSS
SIP
IP PSAP
Diameter
SIP
SIP
P-CSCF
IP-PBX
SIP
S-CSCF
SIP
MRFC
MS
MS
SIP
BGCF
SIP
MGCF
ISUP
IP-phones
PSAP Selection
Left to Implementation
(IP-Centrex,
DSL, Cable)
MGW
IP-phones
SS7
H.248
TDM
Selective
Router
CAMA
E-MF
RTP
Connectivity to
Legacy Emergency
Services Network
Legacy PSAP
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Potential Long Term
IMS Emergency Services Network
Call Delivered to
IP PSAP with
Location
Location is Used to
Determine PSAP
SIP
Access
DNS
ENUM
RTP
RTP
Customer
Home
Network
HSS
Diameter
SIP
Backbone
Packet
Network
PSAP
Selection
AS
AS
AS
SIP
SIP
P/SCSCF
SIP
I-CSCF
SIP
S-CSCF
P-CSCF
IP PSAP
SIP
SIP
MRFC
MS
SIP
SIP
MS
SIP
BGCF
SIP
MGCF
ISUP
RTP
IMS Emergency
Services Network
H.248
SS7
MGW
Call Enters IMS ESNet
With Location
TDM
CAMA
E-MF
OR
Call Delivered to Legacy
Network Without Location
(Query for Location Needed)
Selective Router
CAMA
E-MF
Legacy PSAP
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Emergency Call Delivery
VoIP to IP PSAP
SIP Application
Servers
VSP VoIP Network
HSS
PIDF-LO
SIP Application
Servers
PIDF-LO
IMS ES Network
I-CSCF
P-CSCF
IP PSAP
MRF
S-CSCF
MGCF
PSTN
ANI
STP
Legacy
EO
MGW
ANI
Legacy ESNet/PSAP
• Call Originates with Location
• Location used for PSAP Selection
• Call Delivered with Location
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Emergency Call Delivery
VoIP to Legacy PSAP
SIP Application
Servers
VSP VoIP Network
HSS
PIDF-LO
SIP Application
Servers
PIDF-LO
IMS ES Network
I-CSCF
P-CSCF
IP PSAP
MRF
S-CSCF
MGCF
PSTN
ANI
STP
Legacy
EO
MGW
ANI
Legacy ESNet/PSAP
• Call Originates with Location
• Location Could be used for PSAP Selection
• Call Delivered only w/Callback (ANI)
• Query Mechanism Needed for Location
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Emergency Call Delivery
Legacy PSTN to IP PSAP
SIP Application
Servers
VSP VoIP Network
HSS
PIDF-LO
SIP Application
Servers
PIDF-LO
IMS ES Network
I-CSCF
P-CSCF
IP PSAP
MRF
S-CSCF
MGCF
PSTN
ANI
STP
Legacy
EO
MGW
ANI
Legacy ESNet/PSAP
• Call Originates with only Callback (ANI)
• Mechanism to Provide Location and
PSAP Selection Required
• Call Delivered with Location
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Emergency Call Delivery
Legacy PSTN to Legacy PSAP
SIP Application
Servers
VSP VoIP Network
HSS
PIDF-LO
SIP Application
Servers
PIDF-LO
IMS ES Network
I-CSCF
P-CSCF
IP PSAP
MRF
S-CSCF
MGCF
PSTN
ANI
STP
Legacy
EO
MGW
ANI
Legacy ESNet/PSAP
• Call Originates with only Callback (ANI)
• Mechanism to Provide Location and
PSAP Selection Required
• Call Delivered only w/Callback (ANI)
• Query Mechanism Needed for Location
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Emergency Services - Additional Topics
Bridge/Transfer
– Including Location, if Feasible
Alternate Routing
Default Routing
Wireless Phase 2 Updates
TTY/TDD
3rd Party Call Centers
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BACKUP SLIDES
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FUNCTIONAL ELEMENTS DESCRIPTIONS
Home Subscriber Server (HSS)
Application Server (AS)
Call Session Control Function (CSCF)
Breakout Gateway Control Function (BGCF)
Media Gateway Function (MGW)
Media Gateway Control Function (MGCF)
Multimedia Resource Function Controller (MRFC)
Multimedia Resource Function Processor (MRFP)
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Home Subscriber Server (HSS)
HSS
Diameter
Presence, Location and Profile
End-User Identity
Private and Public End-User Information
Registration Information
Service Initiation Information
Subscriber Service Profile (SSP)
– Downloaded to CSCF at Registration
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Application Server (AS)
AS
AS
AS
Diameter
SIP
Contains Call Related Application Logic
Facilitates a Service Creation Environment
Queried by S-CSCF in Real Time to Execute Logic
Generally Specialized for Each Service
May Provide Gateway to Legacy Applications (e.g.
AIN)
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Call/Session Control Function (CSCF)
Diameter
P-CSCF
I-CSCF
SIP
S-CSCF
SIP
SIP
SIP
SIP
CSCF – Processes SIP Signaling
P-CSCF
–
–
–
First Point of User Contact
Authenticates user
May Include Policy Functions
C-CSCF
–
–
–
–
Central Node of Control Plane
Acts as Registar for User (Downloads SSP from HSS)
Invokes Application Servers
Performs Primary Routing Function
I-CSCF
–
–
–
Located at Edge of Administrative Domain
Is the Ingress Network Point Defined in DNS
Shields Network Topology from External Networks
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PSTN (Circuit Switched) Gateway
SGW
ISUP
SIP
BGCF
SIP
SIP
MGCF
H.248
MGW
TDM
BGCF – Routes to Gateway Based Upon Telephone
Number
MGCF – Controlling Function for SGW and MGW
SGW – Provides Signaling Conversion Between SIP
and ISUP
MGW – Provides Conversion between RTP and
TDM
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Multimedia Resource Function (MRF)
SIP
MRFC
MS
MS
Offers Services Such as Conferencing
MRFC – SIP User Interface toward S-CSCF
MRFP – Controls the Media Server (MS)
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