ETSI TISPAN#10Bis 10Btd121r1

ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

Title Comparison of ITU-T and ETSI TISPAN NGN Functional Architectures Source France Telecom Contact Bruno CHATRAS ([email protected]) To WG2 and System Architecture WI Ref. (if any)

Document for: Decision Late submission Discussion Information X

This contribution is an attempt to compare the ITU-T NGN Functional Architecture with the ETSI TISPAN NGN Architecture. The following reference documents have been used to draw this comparison:

ITU-T documents (from the January meeting of ITU-T SG13)

- Draft Recommendation Y.NGN-FRA Version 0.1 (TD133) - Draft Recommendation Y.IFN (TD103Rev1) - Draft Recommendation Y.PIEA (TD109) - Draft Recommendation Y.NGN-RACF Version 8.1 (TD81r2)

ETSI documents (http://portal.etsi.org/docbox/tispan/Open/)

- ES 282 001 TISPAN NGN Functional Architecture – Release 1 - ES 282 002 TISPAN NGN PSTN/ISDN Emulation Subsystem (Softwitch-based) - ES 282 003 TISPAN Resource and Admission Control Subsystem - ES 282 004 TISPAN Network Attachment Subsystem - ES 282 007 TISPAN IP Multimedia Subsystem core component - TS 182 012 TISPAN NGN PSTN/ISDN Emulation Subsystem (IMS-based)

The contribution also includes a number of proposals in order to improve alignment between the two set of specifications. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

I. Overview

Figure 1 and 2 provide an overview of the ITU-T and ETSI TISPAN NGN architectures. Both architectures are in line with regards to the separation between transport and services defined in ITU-T Recommendation Y.2011.

Applications Applications ANI

Application Support Functions & Service Support Functions Other User subsystems Service Layer profiles Core IMS Service User s Profiles Service Control n PSTN/ISDN O o i t Functions U t

Service stratum h

s Emulation c e e n r

subsystem r u E

Transport User u e t Network Resource and Profiles i p t n w

Attachment Admission m e Control Functions Control Functions e o m n r e Transport Control Functions t k g

Network s a End-User

n Other Functions Attachment a Networks Subsystem M Resource and Admission Control Transport Functions Subsystem UNI NNI Transport Layer Transport stratum Control Transfer Functions Media Management Note: UNI/NNI/ANI are not meant to represent any specific interfaces. (This typeFigure of note is 1:written ITU-T in TR-FRA NGN word file.) Architecture Figure 2: TISPAN NGN Architecture

II. Transport Layer/Stratum

II.1 Overview The ITU-T transport stratum comprises two groups of functions: the transport processing functions and the transport control functions. The later group of functions is further divided into Resource and Admission Control Functions (RACF) and Network Attachment Control Functions (NACF) and a user profiles function.

The TISPAN Transport Layer is equivalent to the ITU-T Transport Stratum. It comprises a set of transport processing functional entities (also known as transfer sub-layer functional entities) and two control subsystems: The Resource and Admission Control Subsystem (RACS) and the Network Attachment Subsystem (NASS).

The TISPAN Resource and Admission Control Subsystem (RACS) corresponds to the ITU-T Resource and Admission Control Functions (RACF).

The TISPAN Network Attachment Subsystem (NASS) corresponds to the ITU-T Network Attachment Control Functions (NACF), except for the Profile Database Function (PDBF) functional entity which in the ITU-T case is equivalent to the User Profile Function sitting outside the NACF. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

II.2 Transport processing

Figure 3 and 4 provide an overview of the transport processing functional entities identified in the ITU-T and ETSI TISPAN NGN architectures.

TC-T1 TC-T2 TC-T3 S-T2 TC-T5 TC-T6 TC-T4 S-T1 S-T3 TC-T9 S-T5 S-T4

T-9:Signalling T-ON1 Gateway FE

T-U1 T-4:Access Relay FE T-8: Media Resource Processing FE

T-6: Interconnection T-ON2 T-1: Access Media Border Gateway FE T-U2 Gateway FE Core Transport Functions

T-7:Trunk Media T-ON3 Gateway FE T-3: Edge Node T-5:Access Border T-2:Access Node FE T-U3 Access Transport Functions FE Gateway FE

Access Transport Processing Core Transport Processing Figure 3: ITU-T Transport processing functions

e1 Re Ia p1 Mp Mn Ie Ia

SGF U A-MGF O s t e MRFP h

r T-MGF e

q n u e i t p

ARF w m o e r k n s t RCEF C-BGF I-BGF L2TF Transfer Functions

Figure 4: ETSI TISPAN Transport processing functions

No fundamental differences exist between the two set of entities. The mapping between transport processing entities identified in the ITU-T and TISPAN architectures is as follows:

- Access Media Gateway Functional Entity (AMG-FE): This entity corresponds to the A- MGF in the TISPAN architecture.

- Access Node Functional Entity (AN-FE): The ETSI TISPAN architecture identifies a notion of Access Node similar to the AN-FE. However, it does not formally specify a functional entity for representing those functions.

NOTE: In future versions of draft Recommendation Y.FRA, this functional entity is likely to be replaced by the Transport Enforcement Functional Entity (TE-FE) and/or the Policy Enforcement Functional Entity (PE- FE) as a result of alignment between draft Recommendations Y.FRA and Y.RACF.

- Trunk Media Gateway Functional Entity (TMG-FE): This entity corresponds to the T- MGF in the TISPAN architecture. Unlike the T-MGF. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

- Access Relay Functional Entity (AR-FE): This entity corresponds to the ARF entity of the TISPAN architecture

- Media Resource Processing Functional Entity (MRP-FE): This entity corresponds to the MRFP in the TISPAN architecture.

- Signalling Gateway Functional Entity (SG-FE): This entity corresponds to the SGF in the TISPAN architecture.

- Edge Node Functional Entity (EN-FE): This entity corresponds to the RCEF and L2TF entities of the TISPAN architecture.

- Access Border Gateway Functional Entity (ABG-FE): This entity corresponds to the C- BGF in the TISPAN architecture. However, unlike the C-BGF the ABG-FE does not support IPv4/IPv6 conversion. There seems to be an implicit assumption in the ITU- T specifications that the same IP version is used in a core network and in the access networks it connects.

- Interconnection Border Gateway Functional Entity (IBG-FE): This entity corresponds to the I-BGF in the TISPAN architecture. However, the IBG-FE may in addition support media conversion and encryption functions, while in the ETSI TISPAN specification this functionality is supported in an MRFP only.

NOTE: This functional entity is likely to be replaced by the Transport Enforcement Functional Entity (TE-FE) and/or the Policy Enforcement Functional Entity (PE-FE) as a result of alignment between draft Recommendations Y.FRA and Y.RACF.

II.3 Transport control

II.3.1 Network Attachment Figure 5 and 6 depict the set of functional entities supporting network attachment procedures as identified in the ITU-T and TISPAN architectures.

S-TC1 S-TC2 S-TC3 S-TC4 S-TC5

NACF RACF

T-12: T. User Profile FE T-14: Policy Decision FE TC-ON1 T-13: T. Location T-11: T. Authentication TC-TC1 & Authorization FE Management FE TC-TC1 T-15: Access Transport T-16: Core Transport Resource Control FE Resource Control FE T-10: TC-U1 T. Network Access Control FE

TC-T1 TC-T2 TC-T3 TC-T5 TC-T6 TC-T4 TC-T9 ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

Figure 5: ITU-T Network Attachment Functions

Service control subsystems and applications Resource e2 e2 e4 and CLF Admission Control a2 a4 e5 Subsystem

CNGCFCPECF NACF UAAF PDBF

e3 a1 a3

e1 e1 TE CNG ARF AMF UE Figure 6: ETSI TISPAN Network Attachment Subsystem

Although the overall network attachment functionality and the two set of functional entities look very similar, significant differences seem to exist with regard to the set of functions allocated to each entity. The mapping between network attachment functional entities identified in the ITU-T and TISPAN architectures is as follows:

- Network Access Control Functional Entity (NAC-FE): This entity roughly corresponds to the NACF of the NASS in the TISPAN architecture. However it supports a number of additional functions three of which being clearly beyond the scope of the TISPAN NACF:

- Provide an access network identifier to the terminals; - Control firewall policy; - Control Network Address and Port Translation (NAPT) policy; - Control security policy.

NOTE: It should be noted that the current definition of the NAC-FE in ITU-T may be erroneous as it does not seem consistent with the architecture depicted in Figure 5, where the NAC-FE has an interface towards the ARF only and therefore can hardly perform firewall/NAPT control.

- Transport Authentication and Authorisation Functional Entity (TAA-FE): This entity corresponds to the UAAF entity of the NASS in the TISPAN architecture.

- Transport User Profile Functional Entity (TUP-FE): This entity corresponds to the PDBF entity of the NASS in the TISPAN architecture with additional functionality allocated to the CLF (e.g. presence status) in the TIPSAN architecture.

- Transport Location Management Functional Entity (TLM-FE): The role of this entity is not defined in the current version of the ITU-T Recommendation.

The CNGCF and AMF entities of the TISPAN NASS architecture do not seem to have a counterpart in the ITU-T architecture.

II.2.2 Resource and Admission Control See companion document. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

III. Service Layer/Stratum

III.1 Overview

ITU-T and ETSI TISPAN have used different approaches to the specification of the service layer/stratum architecture.

The TISPAN architecture uses a subsystem oriented approach. Each subsystem relies on its own architecture model and is specified independently from the others. This enables the addition of new subsystems over the time to cover new demands and service classes. It also provides the ability to import and adapt subsystems defined by other standardization bodies such as the IMS.

ITU-T Recommendation FRA specifies a generic functional model (See figure 8) of the service layer/stratum that is independent of the type of services and protocols used. This model may then be instantiated into more specific models, known as service components. ITU-T service components are roughly equivalent to ETSI TISPAN subsystems in the service layer.

In both cases, only two components/subsystems have been specified within the scope of Release 1 standards: a component/subsystem for supporting multimedia services (IP Multimedia Subsystem) and a component/subsystem for supporting PST/ISDN emulation.

NOTE: Whether ITU-T components are located inside the service stratum as ITU-T FRA suggests or spans both the service and transport stratum as suggested in the draft Recommendations where these components are defined has to be clarified.

Application Support Functions & Service Support Functions

A-S1 A-S2 A-S3 A-S4 A-S5 A-S6

Service Control S-5: Service User S-14: Media Resource Profile FE Broker FE S-6: Service S-4: Subscription Authentication Locator FE S-15 Multimedia & Authorization FE S-12 Network Services FE Signaling S-ON1 Interworking FE S-U1 S-11: User S-2: Proxy Call S-3: Interrogating Signaling Session Control FE S-1: Serving Call Session Call Session Control FE S-ON2 S-U2 Interworking FE S-7: Interconnection Control FE Border Gateway Control FE

S-10 Breakout Gateway Control S-ON3 S-13: Media S-8: Access FE Resource Gateway Control Control FE FE S-9: Media Gateway Control FE

S-TC1 S-TC2 S-T1 S-TC3 S-T2 S-TC4 S-T3 S-T4 S-TC5 S-T5

Figure 8: ITU-T Service Stratum generic model

TISPAN documentation does not include a generic model of the service layer similar to that defined in ITU-T Recommendation Y.FRA. However, this is not seen as a source of misalignment as it is not expected that detailed signalling requirements and protocol ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006 specifications will be developed for the reference points identified by this generic model. Detailed signalling requirements and protocol specifications are expected to be developed within the framework of each service component.

Hence, it appears that a key objective of ITU-T and ETSI TISPAN shall be to ensure alignment between ITU-T service stratum components and TISPAN service layer subsystems. However, it remains important to also ensure that there is no fundamental contradiction between the generic model and the TISPAN service layer subsystems specifications. Annex 1 describes a tentative mapping between this generic model and the service layer defined in the TISPAN architecture. This mapping shows a high degree of compatibility between the two models, except on the following issues:

- The ITU-T MGC-FE MAY also incorporates the functionality of an IM-SSF while the TISPAN specification requires that the IM-SSF be accessed via an I-CSCF or an S- CSCF only.

- ITU-T identifies an optional direct reference point between the IBC-FE and the transport processing functions while the TISPAN IBCF controls transport processing functions via the RACS only.

III.2 Subsystems and components

III.2.1 IP Multimedia Subsystem/Component (IMS)

The ITU-T IMS component is described in draft Recommendation Y.IFN. This is merely a pointer to the set of 3GPP UMTS Release 6 and 3GPP2 Revision A specifications that define the IMS architecture. Hence, this Recommendation is suitable for mobile access only.

The ETSI TISPAN specification for the IMS (ES 282 007) is based on 3GPP UMTS Release 7 and incorporates the extensions required to make the architecture suitable for use with both fixed and mobile access environments and for using the IMS as a transit network.

III.2.1 PSTN/ISDN Emulation Subsystem (PES)

Both ITU-T and ETSI specifications describe alternative functional architectures for structuring a PSTN/ISDN Emulation Subsystem/Component. Draft Recommendation Y.PIEA defines these alternatives in the ITU-T case.

The ITU-T Call Server based alternative is similar to the ETSI TISPAN Softwitch approach described in ES 282 002.

The ITU-T IMS-based alternative is identical to the ETSI TISPAN IMS-based approach described in TS 182 012. However, the ITU-T specification is not in line with the latest (approved) version of the ETSI specification. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

IV. Proposals

It is proposed that the following changes be made to ITU-T Draft Recommendations in order to improve alignment with the ETSI TISPAN NGN functional architecture

Changes to Y.FRA

1) Add IPv4/IPv6 conversion to the list of functions supported by the ABG-FE

Rational: There is no obvious reason to place restrictions on the version of IP used on a transport segment.

2) Remove the support of policy control for security, firewall and NAT from the list of functions supported by the NAC-FE.

Rational: These functions are not related to the NAC-FE and are already encompassed by other functional entities (PE-FE, PD-FE…).

3) Move temporary data from the TUP-FE to the TLM-FE

Rational: Temporary data should be associated with the FE handling location management in the access network (i.e. the TLM-FE) rather than stored in the TUP-FE, which may reside in a different network (i.e. visited vs. home network).

4) Ensure that the CNGCF is covered in the Management specifications.

Rational: Dynamic CPE configuration is an essential feature of the NGN. As no functional entity for supporting this seems to be identified as part of the Network Attachment Functions, there is a need to ensure that the required functions are documented in the ITU- T NGN Management Recommendations

5) Split the NAC-FE into two entities one of which being equivalent to the AMF (i.e. a front-end to the address allocation function and to the TUP-FE).

Rational: The current model is suitable for DHCP-based configuration but makes it difficult to represent PPP/RADIUS configurations.

6) Remove the IM-SSF from the list of functions supported by the MGC-FE

Rational: Access of to IN services is not a function of a media gateway controller. Moreover, in the IMS case, an alternative route already exists for accessing IN services via the IM-SSF from the PSTN. The MGCF routes the incoming session to an I-CSCF which in turns routes the session to the IM-SSF via the Ma reference point.

7) Remove the direct reference point between the IBC-FE and the transport functions. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006 Rational: Having two different paths for controlling transport resources (i.e. one via the RACF, one bypassing the RACF) will make transport resource management unnecessarily complex.

Changes to Y.IFN

The text shall be updated to refer to a version of the IMS specifications that is suitable for supporting both fixed and mobile access.

Changes to Y.PEIA

The text shall be brought in line with the approved version of ETSI TS 182 012. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006

Annexe 1: Mapping ITU-T and ETSI TISPAN service layer entities

The following table describes the mapping between generic functional entities identified in draft Recommendation Y.FRA and the functional entities of the ETSI TISPAN IMS and IMS-based subsystems.

ITU-T ETSI TISPAN Comments FRA S-CSC-FE S-CSCF NOTE 1 P-CSC-FE P-CSCF Access to NASS does not seem to be taken into account.

NOTE 1 I-CSC-FE I-CSCF Support of transit scenarios does not seem to be covered. The ITU-T I-CSCF-FE does not have access to application servers while the TISPAN I-CSCF has. SL-FE SLF SUP-FE No direct mapping This entity corresponds to the part of the UPSF of the TISPAN architecture that manages the user profile. SAA-FE This entity corresponds to the part of the UPSF of the TISPAN architecture that supports Authorisation and Authentication. IBC-FE IBCF Whether the IBC-FE incorporates the TISPAN IWF entity should be clarified.

ITU-T identifies a direct reference point between the IBC-FE and the transport processing functions while the TISPAN IBCF controls transport processing functions via the RACS only. AGC-FE AGCF Unlike the AGC-FE, the AGCF for TISPAN Release 1 does not support ISDN access. MGC-FE MGCF + IM-SSF The ITU-T MGCF-FE also incorporates the functionality of an IM-SSF.

Support of transit scenarios does not seem to be covered. BGC-FE BGCF Support of transit scenarios does not seem to be covered. USIW-FE No direct mapping This functional entity has not explicit counterpart in the TISPAN architecture. Part of its role is fulfilled by the P- CSCF. NSIW-FE This functional entity has not explicit counterpart in the TISPAN architecture. Part of its role is fulfilled by the IBCF and MGCF MRC-FE MRFC MRB-FE No counterpart May be easily included in TISPAN Release 2 MLT-FE This entity has no direct counterpart in the TISPAN architecture. ASF Type I or Other subsystems. AS-FE ASF Type I (SIP AS and OSA AS) IN-IN-FE SCP APL-GW- OSA GW FE APL- SIP AS acting as a SCIM SCM-FE SS-FE SIP AS acting as an IM-SSF NOTE1: Although the entities described in Y.FRA are intended to be protocol independent some of the descriptions include protocol details that are not fully in line with the specification of the concrete service components. ETSI TISPAN#10bis 10bTD121r1 Sophia Antipolis, 3 - 7 April 2006