ims - enabling services, wherever the customer and whatever the access duncan mills - vodafone...

IMS - enabling services, wherever the customer and whatever the access

Duncan Mills - Vodafone

Stuart Walker – Leapstone

Sponsored by

Copyright 2005: MultiService Forum

Agenda

• From NGN to Fixed Mobile Convergence• 3GPP and TISPAN overview• The IMS Architecture• Service Layer• MSF and IMS• Q&A


Where has NGN come from?

• In fixed line there has been a long term move towards a VoPacket replacement for PSTN

• Driver has always been to reduce Opex in fixed line networks by optimising bandwidth usage, whilst replacing outdated TDM switching fabric.

– Compressed speech into less than 64kbps channels– Further optimisation using VAD, Silence Suppression, AAL2 or IP multiplexing

yields significant reduction in core network bandwidth requirements.

• Drivers in 3GPP are more service related– IMS is borne out of a need for ‘feature rich’ service– Bandwidth requirements and their impact on capacity on the Radio interface

are actually worse than now.

• Now, IMS possibly provides the final piece in the business case for NGN that makes the decision to move justifiable…

FIXED MOBILE CONVERGENCE


Different drivers = same end goal?

• If fixed wants OpEx saving and fabric replacement, but mobile wants new services, how come the answer is the same architecture for both?– Both sides see the advantage to common, seamless services over any

access. – IMS is defined in 3GPP so it has all the requirements for mobile

operators built in.– SIP controlled voice is already available in fixed networks (particularly

for enterprise customers) so it extends existing technology.

• However, an IMS deployment supporting only voice does not make sense– Mobile has to go from no installed base to the full suite of available

service to be justifiable.– IMS delivering single services (voice, PoC etc) is too expensive and too

limiting in the service set it facilitates


Who gains from Fixed and Mobile convergence?

• Manufacturers– Single development stream reduces R&D costs– Next gen. networks = next gen. device = new revenue

streams – to deploy it, operators have to buy it!• Has to be priced to make initial CapEx recovery for the

operator a short term deliverable.

• Operators– Optimised ‘all IP’ network reduces OpEx– Opens the fixed market’s customers to mobile operators and

vice versa. – Next Gen Services = new revenue streams – to use it, the

customers have to buy it• Has to be the right service set, priced to make the

services attractive to the customer


Who gains from Fixed and Mobile convergence?

• End Users– Common service set available regardless of device they use,

the location they are in or the access medium they are using.

– New services available – location based, blended interfaces combining multiple inputs into a single presentation.

– Single sign on – one identity that goes everywhere with you.

BUTThe food chain runs from the End User upwards.

What services do they want? When will they buy them? At what price point?


3GPP IMS - Architecture

I-CSCF

AS

OSA-GW

IM-SSF

MGCFP-CSCF

GGSN

PDF

Gm

ShCx

Si

ISC

Mw

Mw

Mi

Mb

Mj

Mr

Mm

Mb

Multimedia Content

Mk

Legacy Bearer

ISUP or BICC

MRFC

UE

MRFP

Gm

HSS

BGCF

IM-MGW

Mg

SLFDx Dh

Gq

Go

Mp Mn

3GPP Profile SIP

Other Control Plane

Bearer

Legacy protocol

S-CSCF


TISPAN – Top Level ArchitectureTaken from TISPAN WI02007 (Overall Functional Architecture)

Oth

er netw

orks

Other subsystems

Core IMS

PSTN/ISDN Emulationsubsystem

Custom

er Prem

ises Equipm

ent

Service Layer

Transport Layer

Transfer Functions

Resource and Admission Control

Subsystem

Network Attachment Subsystem

Applications

Userprofiles


TISPAN – IMS Core Taken from TISPAN WI02029 (Functional Architecture IMS)

Oth

er IP

Ne

two

rks

IP Transport (Access and Core)

T-MGF

I-BGF

AS

UPSF

P-CSCF

I/S-CSCF

BGCF

SLF

ChargingFunctions

IWF

UE

« Core IMS»

Mw

Mw/Mk/Mm

Mr

Mg

Mj

Mi

Mp MnGm

Gq

ISC

Cx Dx

Dh

Sh

Ic

Rf/Ro

Rf/RoIb

Ia

Id

PS

TN

/ISD

N

SGFMRFC MGCF

MRFP

Resource and Admission Control Subsystem

Network Attachment Subsystem

If

Ie

Mw

IBCFMk

Mk


TISPAN NGN mapped on to 3GPP IMS +TISPAN add ons

I-CSCF

AS

OSA-GW

IM-SSF

MGCFP-CSCF

GGSN

PDF

ShCx

Si

ISC

Mw

Mw

Mi

Mb

Mj

Mr

MRFC

UE

MRFP

Gm

HSS

BGCF

IM-MGW

(T-MGF)

Mg

SLFDx Dh

Gq

Go

Mp Mn

S-CSCF

SGF

I-BCF

I-BGF

IWF

PSTN/ISDN

Other IP Networks

IMS Core

TransportNASS

Applications

RACS

CLF, UAAF, PDBF, UPSF

SPDF

A-RACF, SPDF

L2TF, RCEF, AMF

None of these functions are included in the 3GPP architecture

RACS


3GPP IMS applicability to NGN

• In R6, 3GPP IMS has been made ‘Access Independent’– the technology used to transport SIP messages to the edge of

the IMS network does not affect the functionality within the IMS network itself.

• This allows IMS to be applied to any form of Access technology that is capable of transporting SIP control messages to the P-CSCF– WLAN, DSL, Cable Modem, FTTx,

Satellite, Broadband Wireless all become irrelevant – all that matters is SIP presentation to the P-CSCF.

– Only aspect of Access that is relevant is User Equipment capability and QoS.

P-CSCF

I-CSCFMRF

MGW

MGCF

IMSIMS

S-CSCF

SIP ApplicationServersSIP Application

Servers

HSS


Access Independence of IMS

RNCMSC(Server)

SGSNGGSN

CNCNMGW

BSC

UMTS/GPRSUMTS/GPRS

WLANWLAN

CorporateCorporate

P-CSCF

I-CSCFMRF

MGW

MGCF

IMSIMS

S-CSCF

SIP ApplicationServersSIP Application

Servers

HSS

CDMA 2000CDMA 2000DSL/Cable ModemDSL/Cable Modem

DSLAM/CMTS


IMS as a common ‘middleware’ layer

MRF

IMS CoreIMS Core

RNCMSC(Server)

SGSNGGSN

CNCNMGW

BSC

UMTS/GPRSUMTS/GPRS

SIP ApplicationServers

P-CSCF

I-CSCFS-CSCF

HSS



IMS ApplicationsIMS Applications

MGCF

BGCF

MGW

VoIP Interworking

Elements

IP Bearer NetworkIP Bearer Network


IMS Nodes (1/2)

Database Elements– HSS (Home Subscriber Server)– SLF (Subscription Locator Function)

IMS Control Elements– CSCF (Call Session Control Function)– S-CSCF (Serving CSCF)– P-CSCF (Proxy CSCF)– I-CSCF (Interrogating CSCF)

Control Plane Interworking Elements– MGCF (Media Gateway Control Function)– BGCF (Breakout Gateway Control Function)– SGW (Signaling Gateway)

IM-SSF

I-CSCF

MRF

MGW

MGCF

HSS

CSE(SCP) SIP ApplicationServers

OSA-SCS

sgw

OSA ApplicationServer

S-CSCFP-CSCF

BGFC


IMS Nodes (2/2)

IM-SSF

I-CSCF

MRF

MGW

MGCF

HSS

CSE(SCP) SIP ApplicationServers

OSA-SCS

sgw

OSA ApplicationServer

S-CSCFP-CSCF

BGFC

IMS Service Elements

– AS (Application Server)

External Service and Service

Interworking Elements

– OSA Elements - SCS (OSA Service Capability Server, OSA Framework, OSA Application Server

– CAMEL elements - IM-SSF (IP Multimedia Switching Service Function), CSE (CAMEL Service Environment)

Resource Elements

– Media Resources Function (MRF)

Media Interworking Elements

– MGW (Media Gateway)


Benefits of a SIP control plane

• SIP is an end-to-end signalling protocol used to establish, modify and tear down IP sessions

• The IMS nodes can remain in this SIP signalling path throughout a session, ensuring that the network is always aware of the service:– Allowing the network to control the QoS of the bearer– Allowing the network to invoke rich services on behalf of

the user– Allowing for traditional and new charging models (e.g.

duration-based, A-party pays, A-party pays for the voice, B-party pays for the video etc)


“So what ?”- says the subscriber

Infrastructure with no clear application….. this wouldn’t be the first time


Service Co-ordination

Service Orchestration

Service Brokerage

Service Control

IN with the benefit of hindsight


SIP based service orchestration – Service Velocity and Service Agility

Penetration(number of subscribers using service)

Du

rati

on

(act

ive

se

rvic

e l

ifet

ime)

TraditionalTelcoServices

Short LivedServices

Niche MarketServices

Service Velocity – new applications and services to market quicker to address the short lived service market

Service Agility – flexibly bundle applications into customer products to address niche subscriber marketsNew market – economically

realizable through faster and more flexible service layer


IMS Service Orchestration Model

S- CSCF

Parlay AppgsmSCF

I SCI SC

I SCCAMEL OSA API

OSA SCSI M- SSF

SI P ApplicationServer

Mw

P/ I CSCF

HSS

Cx

Sh

Si

MAP

Session Control


Service Logic

Service I nteraction Management

S-CSCF - Subscriber service profile pulled from HSS at Registration time.

Multiple profiles per subscriber (profile per alias)

Profile is a list of priority ordered services point triggers SPT.

SPT = boolean expression using

SIP Method

SIP Headers and Contents

Session Case

SDP contents

Service Interactions handled through a SCIM function, depicted as part of the SIP AS although not really defined.

Service profile updates pushed to S-CSCF from HSS.


MSF R2 Service Orchestration Model

Call Agent

Service Broker

Parlay App

IF 9IF 9

I F 9 I F 11

Parlay / Parlay XGateway

Service LogicGateway

SIP ApplicationServer

I F 7

Session Control


Service Logic

Service I nteraction Management

ParlayX App

IF 12

Other ApplicationEnvironments

Call Agent Invokes Service Broker on originating and or terminating side of call. Call Agent can apply embedded service logic before and after invocation of Service Broker.

Service Broker engaged set of priority ordered applications on seven ‘trigger’ conditions (oCallAttempt, oBusy, oNoAnswer, oHangup, tCallAttempt, tBusy, tNoAnswer)

Conflict resolution / Interaction handling implied but not defined.

Permit multiple applications per link in SIP chain for efficiency.


Shared Service Data

DiameterSh

DiameterSh Diameter

Sh

HSS

Shared NetworkDatabase

Buddy ListsAddress Books

Prepaid Balanceetc

ApplicationServers

HSS provides a shared network data repository allowing applications to share subscriber data.

In multi-HSS deployments, Dh interface to SLF is used to locate correct HSS for subscriber.

Sh interface (Diameter) - operations

Sh-Pull (read data)

Sh-Update (modify data)

Sh-Subs-Notify (request notification of data change)

Sh-Notify (notification of change)

Defined Data Sets

Repository Data – opaque data, network defined

IMS Public Identity

IMS User State

S-CSCF Name

Initial Filter Criteria

Location Information

User State

Charging Information

MSISDN


Parlay and ParlayX

Parlay X API’s

CommonThird Party CallCall NotificationShort MessageMultimedia MessagingPaymentAccount ManagementTerminal StatusTerminal LocationCall HandlingAudio CallMultimedia ConferenceAddress List ManagementPresence

Parlay API’s

Framework Call Control

GenericMulti-partyMulti-MediaConference

Content Based Charging Terminal Capabilities Presence and Availability Policy Management Data Session Control Account Management User Interaction Mobility Management Generic MessagingMultimedia MessagingAddress List ManagementPresence

Network Elements

Parlay Gateway

Parlay X Web Services

Parlay Applications

Parlay XApplications

Network Protocols(e.g. SIP, INAP, etc)

Parlay API’s

Parlay X APIs


SIP ASMultiple mechanisms exist for creating SIP applications.

SIP-CPL – Call Processing Language. An XML based scripting language for controlling call services. Designed to be implemented on either network servers or user agent servers via a lightweight CPL interpreter. Limited but safe, no variables, no loops, no ability to run external programs.

SIP-CGI – Common Gateway Interface. Like HTTP CGI, the script resides in a network server and passes message parameters through environment variables and sends instructions back via the standard output. CGI scripts can be written in most programming languages.

SIP Servlet – Servlets are similar to GCI but rather than a separate process messages are passed to class that runs in the JVM on the server. As they are Java based SIP servlets should be portable between server platforms.

JAIN SIP – A low level API that maps directly to the SIP RFC.

JAIN SIP Lite – A high level API; uses a greater degree of protocol abstraction and acts as a high level wrapper around the SIP protocol. Requires much less knowledge of the SIP protocol on the part of the developer than JAIN SIP.


Legacy Service Access via IMS-SSF

SSF function

SIP Proxy or B2BUA

SIP

INAP / TCAP

SIP

IM-SSF function allows access to legacy IN services from the SIP service network.

Acts as a proxy in the SIP domain and as an SSP in the IN domain.

Effectively peers SIP to ISUP and applies the SSP functions. Only works in one direction, i.e. IN services on a SIP network.

Realistically some legacy services may require SIP-I to be delivered to the IM-SSF in order to prevent information loss.

IM-SSF products are commercially available.


Other Service ModelsService Delivery Platforms SDPNo consensus to date on what architectural elements constitute an

SDP Some vendors use the term SDP for their application servers or content delivery solutions, whereas other vendors and service providers tend to include a whole portfolio of products and components such as CRM systems or rating engines in their SDP offering.

In general, an SDP should be seen as a commercial bundle of different products, possibly offered by different vendors.

Some comment elements of SDPs are :-

• Service Execution Platform (e.g. Application Server)- a core element of an SDP providing the deployment andexecution environment for broad range of voice and dataapplications.

• Network Abstraction Layer (e.g. Parlay GW )- a core element of an SDP providing standardized interfaces tocore network elements and services.

• Service Exposure Layer (e.g. Parlay X GW)- an optional element exposing service capabilities (usually viaWeb Services) to 3rd party service providers and enterprises.

• Content Delivery Platform- an optional element usually present in mobile SDPs for theprovisioning of multimedia content to mobile devices.

Network Elements

Web Services

Service ExposureLayer

Network AbstractionLayer

Service ExecutionPlatform

ContentDeliveryPlatform


OSE (OMA Service Environment)

Main components

Application – either in house or third party

Policy Enforcer – applies policies (authorization, authentication, ..) to the interaction between the Application and the Enabler or between Enablers.

Enabler – Intrinsic functions providing access to the underlying network resources. OMA only define interfaces not individual methods for the enabler.

Execution Environment – provides Life Cycle, Load Balancing and other OA&M functions.


Service Orchestration – tricky stuff


Media Specific Applications - SDP Modification

Insulate Applications from the full media awareness – present to them only the media parameters appropriate to their function.

AuthenticationApp

VoiceApp

VideoApp

WhiteboardApp

Service OrchestrationFunctionINVITE

m=audiom=video

m=application

INVITEm=audiom=video

m=application


m=application

INVITEm=audio

INVITEm=audio

INVITEm=video

INVITEm=video

INVITEm=application

INVITEm=application


m=application

Audio

Video

Application

SDP

Audio

Video

Application

SDP

Audio

Video

Application

SDP

Audio

Video

Application

SDP

Audio

Video

Application

SDP

STOREEXTRACT

EXTRACT STORESTORE STORE STORE

EXTRACTEXTRACT

EXTRACT

Treat as a single service chain, SDP ‘components’ updated as the chain progresses. Parallel invocation could reduce latency but needs potentially complex rules to re-combine multiple SIP INVITEs to the destination.


Partial Media Terminating Applications

Applications may terminate the media session (directly or via a shared media server). In such cases there is no onward signalling from the application.

However, the application may have only terminated a single media type; in such cases the Service Orchestration Function should ‘fork’ the INVITE and continue with session establishment and service invocation for the remaining media types.

AuthenticationApp

VoiceApp

VideoApp

WhiteboardApp

Service OrchestrationFunction


m=application


m=application


m=application

INVITEm=audio

INVITEm=audio

INVITEm=video

INVITEm=video

INVITEm=application

INVITEm=application

INVITEm=video

m=application

Audio

Video

Application

SDP

Video

Application

SDP

Video

Application

SDP

Video

Application

SDP

Audio

Video

Application

SDP

STOREEXTRACT

EXTRACT STOREREMOVE STORE STORE

EXTRACTEXTRACT

EXTRACT

AudioMCU

INVITE (conf=xxx)m=audio


MSF Release 2+ (IMSF) - Objectives

Import IMS functions into the R2 architecture in order to :-

• Support nomadicity (roaming) of terminals and users.

• Support inter working between core IMS and MSF R2+– Roaming of IMS subscriber to R2+ network– Roaming of R2+ subscriber to IMS network


MSF Release 2+ (IMSF) – Architectural Snapshot

AG TG SG SBG-NE

DCASCA

RCA

SB

G-N

C

SB

BM

MS

HSS

AS PGWSLG

PA PXA AG = Access Gateway

TG = Trunking Gateway

SG = Signalling Gateway

SCA = Static Call Agent

DCA = Dynamic Call Agent

RCA = Routing Call Agent

MS = Media Server

SBG = Session Border Gateway

BM = Bandwidth Manager

SB = Service Broker

HSS = Home Subscriber Server

AS = Application Server

PGW = Parlay(x) Gateway

SLG = Service Logic Gateway

PA = Parlay Application

PXA = Parlay X Application

P-CSCF

S-CSCFI-CSCF

SCIM

OSEIM-SSF

SDPOSA SCS

1st Gen VoIP End Points IMS End Points


A typical example of a rich voice call

• A has a subscription with fixed operator X• B has a subscription with mobile operator Y• B is roaming to mobile network Z• A calls B – voice call

– A has originating services, B has terminating services

• B adds in video– A has terminating services

• A adds in white-boarding– A has originating services


A typical example of a rich voice call

User

B

DSL/Cable ModemDSL/Cable Modem

DSLAM/CMTS

RNC

GGSN

Network Z UMTS/GPRSNetwork Z UMTS/GPRS

Network X MSF R2+Network X MSF R2+

User

A

SGSN

Network Y IMSNetwork Y IMS

GRXGRXSBG-NEP-CSCF

P-CSCF

RCAI-CSCF

I-CSCF

S-CSCF

DCAS-CSCF

HSS

HSS

ASAS


Summary

• IMS offers the ability to rapidly define and implement services that interact with each other seamlessly, regardless of the access technology and location of the end user.

• Subscribers have their services available to them on multiple types of end user device and with common presentation and identification.

• The access technology no longer governs the service presentation to the end user, and so a vast new range of services is conceivable.


Q & A

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