IP Multimedia Subsystems Overview - My Training on IMS

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: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>

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:+92-1111111@ufone.net;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) inam@mobilink.com 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 !