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A snaphost on an IMS-based PSTN/ISDN Emulation subsystem3GPP – ETSI TISPAN Workshop

22 – 23 June 2004

B.Chatras

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IMS and PSTN/ISDN Emulation

s A lot of similaritiesQTwo session-based control subsystems:

–For supporting multimedia services and PSTN/ISDN services simulation (IMS)–For supporting PSTN/ISDN services emulation

QAbove a managed IP networkQSupporting operators’ requirements

–Quality of service, Security, Charging capabilities, Regulatory constraints....

s Clear BenefitsQEnables the deployment of common control planes/platforms

–Towards a unique infrastructure for supporting multimedia services and TDM- switches replacement

QEnables service convergence –new voice services available to all types of subscribers

QEnables the scope of nomadism to be extended to legacy access lines

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Technical context

s RequirementsQAll PSTN/ISDN services shall remain available and identical (i.e. with the same ergonomics); such that end users are unaware that they are not connected to a TDM-based PSTN/ISDN.QEnd to End ISDN feature transparency shall be ensured for call transiting through the PSTN/ISDN Emulation subsystem.

s Impact on IMSQRequires new entities (residential/access gateways, access gateway controller) with H.248 interfaces.QRequires SIP with encapsulated ISUP.QMost IMS entities re-used unchanged (transparent to the ISUP bodies) or with minor changes (e.g. removal of ISUP body, based on destination).QISDN/PSTN service logic / call model shifted to application servers.

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A candidate IMS-like functional architecture ?

PSTN/ISDN Specificlogic/data

Reference pointsDxx : DIAMETERSxx : SIP or SIP-IHxx : H.248Ixx : TISPAN specific

Oth

er IP N

etw

orks

IP Transport (Access and Core)

T-MGF

I-BGF

MG

Application Servers

Other applications

PSTN/ISDN supplementaryservices and IN services logic) HSS

IBCF

S1S1

S2S2

H1H1

D8D8 H3H3 H2H2

IcIc

D5D5

D6D6

D3D3 D4D4

D1D1

IdId

A-BGF

S-CSCF

BGCF

I-CSCFSLF

S3S3 S4S4

S5S5

S7S7

S9S9

S8S8

D2D2

S6S6

PS

TN

/ISD

N

SGW

ChargingFunctions

IgIg

IgIg

D10D10

MRFC MGCF

MRFP

IWFIbIb

ZZ

AGCF

D9D9

Resource and Admission Control Subsystem

IaIa

Ie

Network Attachment Subsystem

If

S/TS/T

SIP-I

H.248

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Flexible deployment optionsIMS like

PSTN/ISDNEmulation

“TISPAN” IMS

Unified control plane

Functional View Point

Physical View Point

IMS-likePSTN/ISDNEmulation

“TISPAN” IMS

Functional View Point

Physical View Point

PSTN/ISDNEmulation

Control Plane“TISPAN“ IMS

IMS-like PSTN/ISDNEmulation

“TISPAN” IMS

Functional View Point

Physical View Point

PSTN/ISDNEmulation

Infrastructure

“TISPAN” IMSInfrastructure

Common platforms

Enables various degrees of convergence and a wide range of implementation

options

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Options for physical scenarios

s A unique infrastructureQIdentical or similar functional entities from both functional planes are merged in the physical plane into a single plateform.

s Two distinct infrastructuresQVarious physical configurations (incuding a basic softswitch-like approach) can be envisioned for the PSTN/ISDN emulation subsystem, based on different strategies for grouping functional entities into physical platforms.

s Hybrid scenariosQE.g. Platforms implementing MRFC/MRFP and/or MGC/IM-MGW are shared by both subsystems. Other platforms are implemented separatly.

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Backup Slides

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Changes to IMS interfaces/entities s MRFC, MRFP, SLF: Unchanged.

s S/I-CSCF, BGCF: Minor impact due to SIP-I relay.

s MGCF: Interworking procedures impacted by SIP-I.

s HSS: Impacted by the presence of PSTN/ISDN profile information

s Specific entities : AGCF (i.e. RGW/AGW control) and Application Servers hosting « class 5 » service logic.

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Emulation vs Simulation

s PSTN/ISDN SimulationQThe provision of PSTN/ISDN-like services to advanced terminals such as IP-phones. There is no strict requirement to make all PSTN/ ISDN services available or identical, although end users expect to have access to the most popular ones, possibly with different ergonomics.

s PSTN/ISDN EmulationQMimicing a PSTN/ISDN network from the point of view of a legacy terminal by an IP network, through a gateway. All PSTN/ISDN services remain available and identical (i.e. with the same ergonomics); such that end users are unaware that they are not connected to a TDM-based PSTN/ISDN.

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Example configurations

Z H248 ZH248SIP-I

RGW or AGW

RGW or AGW

Z H248 H248SIP-I

RGW or AGW

S/T

DSS1/IUA

Z H248

H248

SIP-I

RGW or AGW

TGW

ISUP

PSTN/ISDN

H248SIP-I

RGW or AGW

V5.2

V5.2/V5UA

ANZ H248