This document provides an overview of the IMS service control model. It discusses why operators are offering more services like IP telephony, presence, and video on demand. It then introduces the IMS as a flexible, standard platform that simplifies developing and deploying new services. The IMS provides a common service infrastructure and increases control and profitability through a unified service environment. Key components of the IMS service control model are also summarized, including service invocation using SIP application servers and initial filter criteria.

1. IMS Service Control
Model
Inam Ullah
Director Product Development
EMI Networks

2. Why More Services?
• Satisfying the Customer’s Communications
Customer’s Needs Wants?
• Customer Loyalty ?
• Filling the data Pipes ?
• Increasing Revenues ?

3. Exemplary IMS Service
• IP Telephony/VoIP
• Presence
• Conferencing
• Media Servers i.e.
• Voice Mail & IVR
• Gaming
• Video on Demand, IPTV
• 3G Doctors

4. IMS Services
Figure Source: Nokia-Siemens Networks

5. Problem for Multiple Services
Provisions?
• The need for a flexible and standard platform to
simplify the development and deployment of
new services

6. Why IMS ? …to avoid the complex
communication network

7. IMS Motivation, Drivers and Opportunities
Increase control and profitability through a common IMS based Service Infrastructure:


The IMS is an open Service Infrastructure providing Service Support Functions that
assist the development/control/integration of services.
IMS is not just a simple SIP-Proxy.
Figure Source: Nokia-Siemens Networks

8. One IMS based Service Infrastructure for
 Fixed Market,
 Mobile Market,
 Hosted
 Enterprise Market

9. Service Invocation
• Serving Proxies receives the request and applies
the filter criteria and routes it to the SIP AS
• The SIP as can act as User Agent(UA) , Back2BACK
User Agent, Proxy Server
• The CSCF may like to remain in the Path of the
Transaction

10. Service Proxy Function
• The Serving-CSCF (S-CSCF) provides a common protocol to SIP-based
application services running on platforms such as SIP Application Server,
and legacy services running on Intelligent Network (IN) and Open
System Architecture (OSA) platforms.
• Filter criteria, which are based on SPTs and described in XML, are
downloaded to the S-CSCF from the Home Subscriber Server (HSS),
thereby defining which service platform or platforms are used; and in
which order, based on information received by the S-CSCF
• Based on the ISC interface, there are several ways in which the IMS
Application Server might interact with the CSCF:
–
–
–
–
–
Act as a terminating user agent (UA)
Act as an originating user agent to originate traffic on behalf of a user
Receive requests
Serve as a proxy function
Act as a third party call control applet

11. Application Server Selection
Service 1
AS1
AS2
AS3
AS4
Service 2
AS1
Representative AS
AS2
AS3
AS4
Representative AS
Ut
Service 3
AS1
AS2
AS3
AS4
Representative AS
UE
Sh:
(for storage of
selected AS)
HSS
ISC
Cx
S-CSCF

12. AS Selection IFC Triggers
Sh
Cx
AS 1
SIP
Interface
ISC
Incoming Call leg
1
S
P
I
2
Sh
HSS
SIP
Interface
Service Logic
3
AS 2
SIP message possibly
with modification by AS1
4.a
INVITE Match Initial Filter Criteria
ISC
Service Logic
5a
SIP message possibly
with modification by AS2
Outgoing Call leg
S-CSCF
Filter Criteria XAS1
Filter Criteria YAS2
4.b
SIP message forwarded by
S-CSCF
6a
SIP message forwarded by
S-CSCF

13. IMS Service Control Model

14. IMS ISC Interface
• An Interface between CSCF and AS that is used
for the control signaling and is a Bi-Directional
Interface
• Based on SIP (RFC 3261)
• Purpose:
– Service Invocation
– Presenting SIP Parameters to the Applications
– Interaction with Service Proxy for Service Provisioning

15. Initial Filter Criteria
• Initial Filter Criteria represents user’s subscribed IMS value
added service
• The iFCs are stored in HSS as a part of user service profile.
• The iFCs are downloaded during the UE registration in IMS
network
• Each iFC consists of
– Trigger Point Which contains set of Service Point Triggers
(SPTs) that are evaluated to Boolean value
• The SPTs are evaluated by Conjunctive Normal Form (CNF)
or by Disjunctive Normal Form(DNF)
• CNF is an AND of ORed. SPTs
• DNF is an OR of AND SPTs

16. XML Schema For iFC
Method =”INVITE” Session Case =”2”
<? Xml version=”1.0” encoding=”UTF-8”?>
<IMSSubscription>
<PrivateID>sip:inam@mediaroutes.com </PrivateID>
<ServiceProfile>
<PublicIdentity> <Identity>sip:inam@advcomm.net</Identity> </PublicIdentity>
<PublicIdentity> <Identity>tel: +923335251992</Identity></PublicIdentity>
<InitialFilterCriteria>
<TriggerPoint>
<SPT>
<ConditionNegated>0</ConditionNegated>
<Method>INVITE</Method>
<Group>0</Group>
</SPT>
<SPT>
<ConditionNegated>0</ConditionNegated>
<SessionCase>2</SessionCase>
<Group>0</Group>
</SPT>
</TriggerPoint>
</InitialFilterCriteria>
<ApplicationServer>
<ServerName>sip:server@mediaroutes.com </ServerName>
<DefaultHandling>1</DefaultHandling>
</ApplicationServer>
</ServiceProfile>
</IMSSubscription>

17. Service Profiles

18. Thanks