IP Multimedia Subsystem
Presenter : InamUllah KhosaHead of Product Development, Turnotech Pakistan
Cornet Research Lab , Muhammad Ali Jinnah University
Presentation Plan
Background - Evolution of 2G, 2.5G and 3G
What is IMS
Standardization Bodies
Functions of IMS
IMS Architecture – The Big Picture
IMS Components and Interfaces
IMS Services Control Model
IMS Protocols
Conclusion
Setting the Stage.
Revisiting the Past !(Network Evolution)
2G
Digital Network
Initially was merely designed for voice communication
Logically divided into Access Network and Core Network
Access Network is composed number of BTS and BSCs
Core Network composed of MSC , GMSC , EIR, HLR, VLR,AUC
Latter 2.5 Enhancements added PS Domain for Packet Data Support
The PS Domain was composed of SGSN and GGSN
GPRS Services support data rate of 56Kbps to 114Kbs
Background ( 2G)
2.5 G
3rd Generation Networks
W-CDMA (UMTS) HSPA
HSDPA HSUPA HSPA+
UMTS-TDD TD-CDMA TD-SCDMA
FOMA Super-Charged Offer users a wider range of more advanced services WAN voice telephony, video calls, and broadband wireless data
3 & 3.5 G
4G
3GPP LTE
improving spectral efficiency
lowering costs
improving services
LTE air interface is a completely new system based on
OFDMA in the downlink
SC-FDMA (DFTS-FDMA) in the uplink
Flash-OFDM
adaptation to severe channel conditions
Robust against narrow-band co-channel interference
High spectral efficiency
Low sensitivity to time synchronization errors
The Birth of IMS (the New Kid)
New Kid –IMS Block Perspective
What is IMS ?
IP Multimedia Subsystem
Architectural Framework
Overlay Network (PS and CS Networks)
Support for IP-Based Interactive Multimedia (QoS)
Mandatory Support for IPV6
Signaling based on IETF Protocol SIP , DIAMETER and COPS
Core and Access
Integration with PSTN
Access Independent
Wireless ( UMTS , WLAN, WiMAX)
Wired ( DSL)
Overlay Network to PS and CS
IMS Standardization
Worldwide Interoperability
3rd Generation Party Project (3GPP)
Groups of Telecommunications Associations
ITU , ETSI, ARIB/TTC, China Communications Standards Association,
Alliance for Telecommunications Industry Solutions(North-America),
Telecommunications Technology Association (South Korea)
Internet Engineering Task Force (IETF)
Technical Specifications TSpecs.
3GPP Releases
3GPP and 3GPP2
3GPP standardization is based on IMT-2000 which uses
W-CDMA as air interface
3GPP2 standardization is based on IS-95 which uses
CDMA2000 as air interface
High Level Requirements Provisioning for the QoS Negotiation at the start of
session and during End to End Quality of Service for Voice Sessions Roaming
Inter-operator QoS negotiations Services provided by Home Network and Visiting Network
Mandatory default set of media types to ensure interop ( audio:AMR, video: H.263)
Access independence (GPRS, fixed, LAN) Support for session-oriented non-3GPP Internet apps
Can’t we Live without it ? Surely We Can But what about the Operators and Service
Providers? Involved parties
Operators, Users, Content Providers, Legal Authorities, … All-IP network
Interactive Multimedia QoS guarantee Access transparency, seamless handover AAA Billing, Charging
Continued… Services and Service Aggregation
3rd party Application Servers Services: No preferential treatment of voice Voice (VoIP) is just one service, positioned at
same level like any other services
Communication security in IP networks Signaling and Media Access and Core Regulatory requirements (lawful interception)
Key Functions of IMS network
Session Control/Management
Subscription/Registrations Management
Service Control
Charging and Billing
Operations, Administration, Maintenance and
Provisioning (OAM&P/OSS)
Interworking with PSTN
IMS Components Call State Control Functions
P-CSCF, I-CSCF and S-CSCF Home Subscriber Server(HSS) Media Resource Functions
MRFC, MRFP Interworking Functions
BGCF, MGCF, IMS-MGW, WAG/PDG, IMS-IWF, IETF-3GPP IWG
Charging Functions Online Charging System ( OCS) Offline Charging System ( CCF/CDF)
OAM&P Entities
The Big Picture !
IMS Protocols Interfaces
IMS Service Control
Value Added Services are Provided by AS in IMS
Application Servers are defined as a part of Service
Profile
Service Profiles are defined as a Part of User Profile
Each Service Profile contains Initial Filter Criteria
Initial Filter Criterion defines a user’s subscribed service
Sample Initial Filter CriteriaMethod =”INVITE” Session Case =”2”
<? Xml version=”1.0” encoding=”UTF-8”?>
<IMSSubscription>
<PrivateID>sip:[email protected] </PrivateID>
<ServiceProfile>
<PublicIdentity> <Identity>sip:[email protected]</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:[email protected] </ServerName>
<DefaultHandling>1</DefaultHandling>
</ApplicationServer>
</ServiceProfile>
</IMSSubscription>
Initial Filter Criteria Continued…. Each iFC contains Priority, Trigger Point and Application Server, Default Handling and
These iFCs are evaluated on the initial requests
INVITE ,MESSAGE , OPTIONS, SUBSCRIBE
S-CSCF checks filter criteria
Once the AS has been identified
S-CSCF creates Route header to forward message to AS
Additionally, the S-CSCF places itself to the Route header to get back the message
afterwards
In the user part of the SIP URI of this own Route entry
the S-CSCF may enter some state information to understand, that it already received and
processed this message (other ways of providing state are possible)
Continued..
On registration the S-CSCF receives user profile from HSS
Filter criteria determine the services that are applicable to the
collection of Public User Identities of the profile
S-CSCF assesses the criteria in the order of their priority
Filter criteria contain trigger points, which are Boolean
conditions
If the trigger point fires the request goes to the corresponding AS
After receiving back the request the next criteria is checked
Protocols Used in IMS Networks Session Initiation Protocol (SIP)
Registration , Authentication Call Control/Session Establishment Interworking Functions
DIAMETER Next Generation AAA Model Pull/Push Registrations Data User Profiles Service Provisioning/Service Control IMS Charging
Common Open Policy Service ( COPS) QoS Parameters Negotiations
User Identification in IMS
Public User Identities ( IMPU) IMS user has one or more Public User Identity Either a SIP URI or a TEL URI sip:[email protected];user=phone tel:+92-42-664-832356 TEL URIs are required to make calls between IMS/PSTN- Envision: at least one TEL URI and one SIP URI Per
Subscriber
Private User Identity Private User Identities(IMPI)
IMS user has one Private User Identity Have the format of a Network Access Identifier (NAI, RFC
2486) [email protected] Not used for routing SIP messages Used only for subscription identification and authentication Similar function for IMS as the IMSI (International Mobile Subscriber Identification) for GSM Stored on UICC
Home Network Domain Home Network Domain
SIP URI that contains the home network domain name Used to find the address of the home network during registration procedure Only one home network domain
Playgrounds for IMS IMSZONE ( http:imszone.org)
Diameter Stack Home Subscriber Server (Cx,Sh) Online Charging System Offline Charging System Media Server ( MRFC & MRFP) OAM&P Manager and OAM&P Agent
OpenIMSCore – http://openimscore.org FHoSS: Home Subscriber Server SERIMS: P-CSCF,I-CSCF, and S-CSCF OpenIMS Lite: IMS Client
End of this Episode
Thank You !