ETSI ES 282 007 V2.0.0 (2008-05)

Final draft ETSI ES 282 007 V2.0.0 (2008-03)
ETSI Standard


Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
IP Multimedia Subsystem (IMS);
Functional architecture

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2 Final draft ETSI ES 282 007 V2.0.0 (2008-03)



Reference
RES/TISPAN-02052-NGN-R2
Keywords
architecture, functional, multimedia, system
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

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Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
Individual copies of the present document can be downloaded from:
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The present document may be made available in more than one electronic version or in print. In any case of existing or
perceived difference in contents between such versions, the reference version is the Portable Document Format (PDF).
In case of dispute, the reference shall be the printing on ETSI printers of the PDF version kept on a specific network drive
within ETSI Secretariat.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
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If you find errors in the present document, please send your comment to one of the following services:
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No part may be reproduced except as authorized by written permission.
The copyright and the foregoing restriction extend to reproduction in all media.

© European Telecommunications Standards Institute 2008.
All rights reserved.

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DECT , PLUGTESTS , UMTS , TIPHON , the TIPHON logo and the ETSI logo are Trade Marks of ETSI registered
for the benefit of its Members.
TM
3GPP is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners.
ETSI

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3 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
Contents
Intellectual Property Rights.5
Foreword.5
1 Scope.6
2 References.6
2.1 Normative references.6
2.2 Informative references.7
3 Definitions and abbreviations.7
3.1 Definitions.7
3.2 Abbreviations.8
4 Overall architecture .8
5 Overview.9
6 Functional entities .10
6.1 Call Session Control Function (CSCF) .11
6.2 Media Gateway Control Function (MGCF) .11
6.3 Multimedia Resource Function Controller (MRFC) .12
6.4 Breakout Gateway Control Function (BGCF).12
6.5 Interconnection Border Control Function (IBCF) .12
7 Internal reference points.12
7.1 Reference point MGCF - CSCF (Mg reference point) .13
7.2 Reference point CSCF - MRFC (Mr reference point) .13
7.3 Reference point CSCF - CSCF (Mw reference point).13
7.4 Reference point CSCF - BGCF (Mi reference point).13
7.5 Reference point BGCF - MGCF (Mj reference point) .13
7.6 Reference point BGCF - BGCF (Mk reference point) .14
7.7 Reference point CSCF or BGCF - IBCF (Mx Reference Point) .14
8 Value added services architecture .14
8.1 Overview.14
8.2 Reference points.15
8.2.1 Reference point S-CSCF - ASF (ISC reference point) .15
8.2.2 Reference point UPSF - SIP AS or OSA SCS (Sh reference point) .15
8.2.3 Reference point UPSF - IM SSF (Si reference point).16
8.2.4 Reference point ASF - SLF (Dh reference point) .16
8.2.5 Reference point UE - ASF (Ut reference point).16
9 External reference points.16
9.1 Interfaces with entities in the transfer plane.16
9.1.1 Reference Point MGCF - T-MGF (Mn Reference Point) .16
9.1.2 Reference point MGCF - SGF (Ie reference point) .17
9.1.3 Reference point MRFC - MRFP (Mp reference point).17
9.2 Interface with the UE .17
9.3 Interfaces with the user profile .17
9.3.1 Reference point CSCF - SLF (Dx reference point).17
9.3.2 Reference point CSCF - UPSF (Cx reference point) .18
9.4 Interfaces with Charging Functions.18
10 Interconnection with other networks.18
10.1 Interfaces with the PSTN/ISDN .18
10.2 Interfaces with other IP-based service subsystems.18
11 Interface with the Network Attachment Subsystem (NASS) .19
12 Interface with the Resource and Admission Control Subsystem (RACS) .20
Annex A (informative): IMS Access scenarios.21
ETSI

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4 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
Annex B (informative): IMS interconnection scenarios .22
History .25

ETSI

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5 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Telecommunications and Internet
converged Services and Protocols for Advanced Networking (TISPAN), and is now submitted for the ETSI standards
Membership Approval Procedure.
ETSI

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6 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
1 Scope
The present document describes the IP Multimedia Subsystem (IMS) core component of the TISPAN NGN functional
architecture and its relationships to other subsystems and components.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• Non-specific reference may be made only to a complete document or a part thereof and only in the following
cases:
- if it is accepted that it will be possible to use all future changes of the referenced document for the
purposes of the referring document;
- for informative references.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
For online referenced documents, information sufficient to identify and locate the source shall be provided. Preferably,
the primary source of the referenced document should be cited, in order to ensure traceability. Furthermore, the
reference should, as far as possible, remain valid for the expected life of the document. The reference shall include the
method of access to the referenced document and the full network address, with the same punctuation and use of upper
case and lower case letters.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are indispensable for the application of the present document. For dated
references, only the edition cited applies. For non-specific references, the latest edition of the referenced document
(including any amendments) applies.
[1] ETSI ES 282 001: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Functional Architecture Release 1".
[2] ETSI TS 182 006: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Subsystem (IMS); Stage 2 description
(3GPP TS 23.228 v7.2.0, modified)".
[3] ETSI TS 123 218: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); IP Multimedia (IM) session handling; IM call model;
Stage 2 (3GPP TS 23.218)".
[4] ETSI ES 282 010: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Charging [Endorsement of 3GPP TS 32.240 v6.3.0,
3GPP TS 32.260 v6.3.0, 3GPP TS 32.297 v6.1.0, 3GPP TS 32.298 v6.1.0 and 3GPP TS 32.299
v6.4.0 modified]".
[5] ETSI ES 283 024: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); PSTN/ISDN Emulation: H.248 Profile for controlling Trunking
Media Gateways in the PSTN/ISDN Emulation Subsystem (PES); Protocol specification".
ETSI

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7 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
[6] ETSI ES 283 027: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Endorsement of the SIP-ISUP Interworking between the IP
Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks
[3GPP TS 29.163 (Release 7), modified]".
[7] ETSI TS 183 021: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Release 1; Endorsement of 3GPP TS 29.162 Interworking
between IM CN Sub-system and IP networks".
[8] ETSI EN 301 931: "Intelligent Network (IN); Intelligent Network Capability Set 3 (CS3);
Intelligent Network Application Protocol (INAP); Protocol specification".
[9] ETSI ES 201 915-1: "Open Service Access (OSA); Application Programming Interface (API);
Part 1: Overview (Parlay 3)".
[10] ETSI TS 123 002: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Network architecture (3GPP TS 23.002)".
[11] ETSI TS 123 278: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Customized Applications for Mobile network Enhanced
Logic (CAMEL) Phase 4; Stage 2; IM CN Interworking (3GPP TS 23.278)".
[12] ETSI TS 129 278: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); customized Applications for Mobile network Enhanced
Logic (CAMEL); CAMEL Application Part (CAP) specification for IP Multimedia Subsystems
(IMS) (3GPP TS 29.278)".
[13] IETF RFC 3136 (2001): "The SPIRITS Architecture".
[14] IETF RFC 3261 (2002): "SIP: Session Initiation Protocol".
[15] ITU-T Recommendation H.248: "Gateway control protocol".
[16] ETSI TS 182 009: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Architecture to support emergency communication from
citizen to authority [Endorsed document 3GPP TS 23.167, Release 7]".
2.2 Informative references
Not applicable.
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
IP Multimedia Subsystem: As defined in TS 123 002 [10].
NGN IP Multimedia Subsystem: IMS that supports the provision of SIP-based multimedia services and PSTN/ISDN
simulation services to NGN terminals
User Equipment (UE): one or more devices allowing a user to access services delivered by TISPAN NGN networks
ETSI

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8 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AF Application Function
AS Application Server
ASF Application Server Function
BCSM Basic Call State Model
BGF Border Gateway Function
CAMEL Customized Application for Mobile Enhanced Logic
CCBS Call Control on Busy Subscriber
CSCF Call Session Control Function
E-CSCF Emergency-Call Session Control Function
IBCF Intermediate Breakout Control Function
I-BGF Interconnection-Border Gateway Function
I-CSCF Interrogating-Call Session Control Function
IM-MGW IP Multimedia - Media GateWay
IMS IP Multimedia Subsystem
IN Intelligent Network
INAP IN Application Part
IN-SCF Intelligent Network Switching Control Function
IP-CAN IP-Connectivity Access Network
ISDN Integrated Services Digital Network
MGCF Media Gateway Control Function
MGF Media Gateway Function
MM MultiMedia
MRFC Multimedia Resource Function Controller
MRFP Multimedia Resource Function Processor
NAPT Network Address and Port Translation
NASS Network Attachment SubSystem
NGN Next Generation Network
OSA Open Service Access
P-CSCF Proxy-Call Session Control Function
PDF Policy Decision Function
PES PSTN/ISDN Emulation Subsystem
PSTN Public Switched Telephony Network
RACS Resource and Admission Control Subsystem
SCF Switching Control Function
SCIM Service Capability Interaction Manager
S-CSCF Serving-Call Session Control Function
SGF Signalling Gateway Function
SIP Session Initiation Protocol
SLF Subscription Locator Function
SPIRITS Service in the PSTN/IN Requesting InTernet Services
SSF Service Switching Function
TCAP Transaction Capabilities Application Part
T-MGF Trunking-Media Gateway Function
UE User Equipment
UPSF User Profile Server Function
4 Overall architecture
The TISPAN NGN functional architecture ES 282 001 [1] is structured according to a service layer and an IP-based
transport layer (see figure 1).
The service layer comprises the following components:
• The IP Multimedia Subsystem core component (IMS).
• The PSTN/ISDN Emulation Subsystem (PES).
ETSI

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Other networks
User Equipment
 9 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
• Other multimedia subsystems and applications.
• Common components (i.e. used by several subsystems) such as those required for accessing applications,
charging functions, user profile management, security management, routing data bases (e.g. ENUM), etc.
IP-connectivity is provided to NGN user equipment by the transport layer, under the control of the Network Attachment
SubSystem (NASS) and the Resource and Admission Control Subsystem (RACS). These subsystems hide the transport
technology used in access and core networks below the IP layer.
The present document further describes the functional architecture of the IP Multimedia Subsystem (IMS) core
component.
Applications
Service Layer
Other
Subsyst ems
User
profiles
Core IMS
PSTN/ISDN
Emulat ion
Subsyst em
Transport Layer
Network
Attachment
Resource and
Subsyst em
Admission Control
Subsyst em
Transport processing functions

Figure 1: TISPAN NGN overall architecture
5 Overview
The NGN IP Multimedia Subsystem (IMS) supports the provision of SIP-based multimedia services to NGN terminals.
It also supports the provision of PSTN/ISDN simulation services.
Functional entities of an IMS may be used by an operator in support of transit network scenarios. The routing may be
performed, depending on the entity performing the routing, and depending on the traffic case, on signalling information,
configuration data, and/or data base lookup.
The NGN IMS, also known as "Core IMS" is a subset of the 3GPP IMS defined in TS 123 002 [10] which is restricted
to the session control functionalities. Application Servers (AS) and transport/media related functions such as the
Multimedia Resource Function Processor function (MRFP) and the IP Multimedia Gateway Functions (IM-MGW) are
considered to be outside the "core IMS".
Although essentially identical to the 3GPP IMS entities, NGN IMS functional entities might exhibit minor variations in
behaviour, due to differences in access networks and user equipment. However, the NGN IMS architecture defined in
the present document remains compatible with 3GPP-defined IP-connectivity access networks (IP-CAN) and as such
can provide services to user equipment connected to both fixed broadband access and 3GPP IP-CANs (see annex A).
ETSI

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10 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
Figure 2 illustrates the position of the IMS in the overall NGN architecture. The IMS interfaces the following
components:
• User Equipment.
• The Resource and Admission Control Subsystem.
• The Network Attachment Subsystem.
• The PSTN/ISDN.
• The PSTN/ISDN Emulation Subsystem.
• Other multimedia subsystems.
• Charging Functions.
• Network Management Functions.
• Applications and other common architectural elements.
Charging functions
Network Management
Functions
TISPAN
PSTN/ISDN Emulation
Applications/
Subsystem
Common elements
Other MM
Core
User
Subsystems
IMS
Equipment
PSTN/ISDN
Network Attachment Resource and
Subsystem Admission Control
Subsystem

Figure 2: TISPAN IMS and its environment
6 Functional entities
Figure 3 provides an overview of the functional entities that compose the NGN IMS, the reference points between them
and with components outside the IMS.
Unless stated explicitly, the functional entities identified in this clause are identical to those defined in TS 123 002 [10].
Except when highlighting explicitly a difference, the descriptions provided in the present document are intended to
provide tutorial information only and in case of discrepancy with the definitions in TS 123 002 [10], the definitions in
TS 123 002 [10] shall take precedence.
ETSI

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Other IP Networks
PSTN/ISDN
 11 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
Rf/Ro
Charging
Ut
AS
Functions
Sh
Dh
ISC/Ma
UPSF Iw
Rf/Ro
Dx SLF
Cx
IWF
Ib
Network
Attachment Mw
Mx
Ic
Subsystem
I/S-CSCF
IBCF
Mx
«Core IMS» Mk
Mi
BGCF
Mr
e2
Mw
Mj
Mx
Mg
P-CSCF
MGCF
MRFC
Ie
Gq'
Gq'
SGF
Mn
Mp
Gm RACS RACS
MRFP T-MGF
I-BGF
C-BGF
UE
Transport Processing Functions (Access and Core)

Figure 3: NGN IMS overview
6.1 Call Session Control Function (CSCF)
The Call Session Control Function (CSCF) establishes, monitors, supports and releases multimedia sessions and
manages the user's service interactions. For more details see clause 4a.7.1 in TS 123 002 [10].
NOTE: The CSCF can act as Proxy CSCF (P-CSCF), Serving CSCF (S-CSCF) or Interrogating CSCF (I-CSCF).
The P-CSCF is the first contact point for the UE within the IM subsystem (IMS); the S-CSCF actually
handles the session states in the network; the I-CSCF is mainly the contact point within an operator's
network for all IMS connections destined to a subscriber of that network operator, or a roaming
subscriber currently located within that network operator's service area.
This functional entity is identical to the CSCF defined in TS 123 002 [10], except for when acting as a P-CSCF. The
P-CSCF behaviour differs from the behaviour in TS 123 002 [10] by the following main points:
• The e2 reference point is supported to enable the P-CSCF to retrieve information (e.g. physical location of the
user equipment) from the Network Attachment Subsystem (see clause 11).
• The Gq and Iq reference points are not supported but replaced with the Gq' reference point (see clause 12).
Based on local configuration, the I-CSCF may perform transit routing functions (see TS 182 006 [2]).
Further specifications of the P-, S- and I-CSCF are provided in TS 182 006 [2].
Support of emergency communications require the use of an E-CSCF as described in TS 182 009 [16]. For the sake of
simplicity this type of CSCF is not represented on figure 3.
6.2 Media Gateway Control Function (MGCF)
The Media Gateway Controller Function (MGCF) provides the ability to control a trunking media gateway function
(T-MGF) through a standardized interface. Such control includes allocation and deallocation of resources of the media
gateway, as well as modification of the usage of these resources. The MGCF communicates with the CSCF, the BGCF
and circuit-switched networks. The MGCF performs protocol conversion between ISUP and SIP. It also supports
interworking between SIP and non-call related SS7 signalling (i.e. TCAP-based signalling for supplementary services
such as CCBS).
ETSI

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12 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
In case of incoming calls from legacy networks, the MGCF determines the next hop in IP routing depending on
received signalling information.
Based on local configuration, the MGCF may perform transit routing functions (see TS 182 006 [2]).
This functional entity is identical to the MGCF defined in TS 123 002 [10], except that in addition it supports TCAP
interworking. A node implementing this functional entity in an NGN network and a node implementing it in a 3GPP
network may differ in terms of supported resources (e.g. codecs) and configuration.
6.3 Multimedia Resource Function Controller (MRFC)
The Multimedia Resource Function Controller (MRFC), in conjunction with an MRFP located in the transport layer
(see ES 282 001 [1]), provides a set of resources within the core network for supporting services. The MRFC interprets
information coming from an AS via an S-CSCF and control MRFP accordingly. The MRFC, in conjunction with the
MRFP, provides e.g. multi-way conference bridges, announcement playback, media transcoding, etc.
This functional entity is identical to the MRFC defined in TS 123 002 [10], although a node implementing this
functional entity in an NGN network and a node implementing it in a 3GPP network may differ in terms of supported
resources and configuration.
6.4 Breakout Gateway Control Function (BGCF)
The Breakout Gateway Control Function (BGCF) determines the next hop in SIP routing. This determination may be
based on information received in the protocol, administrative information, and/or database access. For PSTN
terminations, the BGCF selects the network in which PSTN breakout is to occur and - within the network where the
breakout is to occur - selects the MGCF. This functional entity is identical to the BGCF defined in TS 123 002 [10],
although a node implementing this functional entity in an NGN network and a node implementing it in a 3GPP network
may differ in terms of configuration (e.g. breakout criteria).
In case of transit the BGCF may have extra functionality for routing transit traffic (see TS 182 006 [2]).
6.5 Interconnection Border Control Function (IBCF)
An IBCF provides application specific functions at the SIP/SDP protocol layer in order to perform interconnection
between two operator domains. It enables communication between IPv6 and IPv4 SIP applications. network topology
hiding, controlling transport plane functions, screening of SIP signalling information, selecting the appropriate
signalling interconnect and generation of charging data records.
Based on local configuration, the IBCF may perform transit routing functions (see TS 182 006 [2]).
This functional entity is identical to the IBCF defined in TS 123 002 [10].
Details are described in TS 182 006 [2].
7 Internal reference points
Unless stated explicitly, the reference points identified in this clause are identical to those defined in TS 123 002 [10].
Except when highlighting explicitly a difference, the descriptions provided in the present document are intended to
provide tutorial information only and in case of discrepancy with the definitions in TS 123 002 [10], the definitions in
TS 123 002 [10] shall take precedence.
ETSI

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13 Final draft ETSI ES 282 007 V2.0.0 (2008-03)
7.1 Reference point MGCF - CSCF (Mg reference point)
This reference point is identical to the reference point MGCF - CSCF (Mg) defined in TS 123 002 [10].
The Mg reference point allows the MGCF to forward incoming session signalling (from the PSTN) to the CSCF for the
purpose of interworking with PSTN networks.
NOTE: The protocol used for the Mg reference point is SIP.
Details are described in TS 182 006 [2].
7.2 Reference point CSCF - MRFC (Mr reference point)
This reference point is identical to the reference point CSCF - MRFC (Mr) defined in TS 123 002 [10].
The Mr reference point allows the S-CSCF to relay signalling messages between an application server function and an
MRFC.
NOTE: The protocol used for the Mr reference point is SIP.
Details are described in TS 182 006 [2].
7.3 Reference point CSCF - CSCF (Mw reference point)
This reference point is identical to the reference point CSCF - CSCF (Mw) defined in TS 123 002 [10].
The Mw reference point allows the communication and forwarding of signalling messaging between CSCFs, e
...

SLOVENSKI STANDARD
SIST ES 282 007 V2.0.0:2008
01-september-2008
=OLWHWHOHNRPXQLNDFLMVNHLQLQWHUQHWQHVWRULWYHWHUSURWRNROL]DQDSUHGQRRPUHåHQMH
7,63$1,3YHþSUHGVWDYQRVWQLSRGVLVWHP,06)XQNFLMVNDDUKLWHNWXUD
Telecommunications and Internet converged Services and Protocols for Advanced
Networking (TISPAN) - IP Multimedia Subsystem (IMS) - Functional architecture
Ta slovenski standard je istoveten z: ES 282 007 Version 2.0.0
ICS:
33.040.01 Telekomunikacijski sistemi Telecommunication systems
na splošno in general
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
SIST ES 282 007 V2.0.0:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ES 282 007 V2.0.0:2008

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SIST ES 282 007 V2.0.0:2008

ETSI ES 282 007 V2.0.0 (2008-05)
ETSI Standard


Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
IP Multimedia Subsystem (IMS);
Functional architecture

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SIST ES 282 007 V2.0.0:2008
 2 ETSI ES 282 007 V2.0.0 (2008-05)



Reference
RES/TISPAN-02052-NGN-R2
Keywords
architecture, functional, multimedia, system
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
Individual copies of the present document can be downloaded from:
http://www.etsi.org
The present document may be made available in more than one electronic version or in print. In any case of existing or
perceived difference in contents between such versions, the reference version is the Portable Document Format (PDF).
In case of dispute, the reference shall be the printing on ETSI printers of the PDF version kept on a specific network drive
within ETSI Secretariat.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
http://portal.etsi.org/tb/status/status.asp
If you find errors in the present document, please send your comment to one of the following services:
http://portal.etsi.org/chaircor/ETSI_support.asp
Copyright Notification
No part may be reproduced except as authorized by written permission.
The copyright and the foregoing restriction extend to reproduction in all media.

© European Telecommunications Standards Institute 2008.
All rights reserved.

TM TM TM TM
DECT , PLUGTESTS , UMTS , TIPHON , the TIPHON logo and the ETSI logo are Trade Marks of ETSI registered
for the benefit of its Members.
TM
3GPP is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners.
ETSI

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SIST ES 282 007 V2.0.0:2008
 3 ETSI ES 282 007 V2.0.0 (2008-05)
Contents
Intellectual Property Rights.5
Foreword.5
1 Scope.6
2 References.6
2.1 Normative references.6
2.2 Informative references.7
3 Definitions and abbreviations.7
3.1 Definitions.7
3.2 Abbreviations.8
4 Overall architecture .8
5 Overview.9
6 Functional entities .10
6.1 Call Session Control Function (CSCF) .11
6.2 Media Gateway Control Function (MGCF) .11
6.3 Multimedia Resource Function Controller (MRFC) .12
6.4 Breakout Gateway Control Function (BGCF).12
6.5 Interconnection Border Control Function (IBCF) .12
7 Internal reference points.12
7.1 Reference point MGCF - CSCF (Mg reference point) .13
7.2 Reference point CSCF - MRFC (Mr reference point) .13
7.3 Reference point CSCF - CSCF (Mw reference point).13
7.4 Reference point CSCF - BGCF (Mi reference point).13
7.5 Reference point BGCF - MGCF (Mj reference point) .13
7.6 Reference point BGCF - BGCF (Mk reference point) .14
7.7 Reference point CSCF or BGCF - IBCF (Mx Reference Point) .14
8 Value added services architecture .14
8.1 Overview.14
8.2 Reference points.15
8.2.1 Reference point S-CSCF - ASF (ISC reference point) .15
8.2.2 Reference point UPSF - SIP AS or OSA SCS (Sh reference point) .15
8.2.3 Reference point UPSF - IM SSF (Si reference point).16
8.2.4 Reference point ASF - SLF (Dh reference point) .16
8.2.5 Reference point UE - ASF (Ut reference point).16
9 External reference points.16
9.1 Interfaces with entities in the transfer plane.16
9.1.1 Reference Point MGCF - T-MGF (Mn Reference Point) .16
9.1.2 Reference point MGCF - SGF (Ie reference point) .17
9.1.3 Reference point MRFC - MRFP (Mp reference point).17
9.2 Interface with the UE .17
9.3 Interfaces with the user profile .17
9.3.1 Reference point CSCF - SLF (Dx reference point).17
9.3.2 Reference point CSCF - UPSF (Cx reference point) .18
9.4 Interfaces with Charging Functions.18
10 Interconnection with other networks.18
10.1 Interfaces with the PSTN/ISDN .18
10.2 Interfaces with other IP-based service subsystems.18
11 Interface with the Network Attachment Subsystem (NASS) .19
12 Interface with the Resource and Admission Control Subsystem (RACS) .20
Annex A (informative): IMS Access scenarios.21
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Annex B (informative): IMS interconnection scenarios .22
History .25

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Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Telecommunications and Internet
converged Services and Protocols for Advanced Networking (TISPAN).
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1 Scope
The present document describes the IP Multimedia Subsystem (IMS) core component of the TISPAN NGN functional
architecture and its relationships to other subsystems and components.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• Non-specific reference may be made only to a complete document or a part thereof and only in the following
cases:
- if it is accepted that it will be possible to use all future changes of the referenced document for the
purposes of the referring document;
- for informative references.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
For online referenced documents, information sufficient to identify and locate the source shall be provided. Preferably,
the primary source of the referenced document should be cited, in order to ensure traceability. Furthermore, the
reference should, as far as possible, remain valid for the expected life of the document. The reference shall include the
method of access to the referenced document and the full network address, with the same punctuation and use of upper
case and lower case letters.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are indispensable for the application of the present document. For dated
references, only the edition cited applies. For non-specific references, the latest edition of the referenced document
(including any amendments) applies.
[1] ETSI ES 282 001: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Functional Architecture Release 1".
[2] ETSI TS 182 006: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Subsystem (IMS); Stage 2 description
(3GPP TS 23.228 v7.2.0, modified)".
[3] ETSI TS 123 218: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); IP Multimedia (IM) session handling; IM call model; Stage
2 (3GPP TS 23.218)".
[4] ETSI ES 282 010: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Charging [Endorsement of 3GPP TS 32.240 v6.3.0,
3GPP TS 32.260 v6.3.0, 3GPP TS 32.297 v6.1.0, 3GPP TS 32.298 v6.1.0 and 3GPP TS 32.299
v6.4.0 modified]".
[5] ETSI ES 283 024: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); PSTN/ISDN Emulation: H.248 Profile for controlling Trunking
Media Gateways in the PSTN/ISDN Emulation Subsystem (PES); Protocol specification".
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[6] ETSI ES 283 027: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Endorsement of the SIP-ISUP Interworking between the IP
Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks
[3GPP TS 29.163 (Release 7), modified]".
[7] ETSI TS 183 021: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Release 1; Endorsement of 3GPP TS 29.162 Interworking
between IM CN Sub-system and IP networks".
[8] ETSI EN 301 931: "Intelligent Network (IN); Intelligent Network Capability Set 3 (CS3);
Intelligent Network Application Protocol (INAP); Protocol specification".
[9] ETSI ES 201 915-1: "Open Service Access (OSA); Application Programming Interface (API);
Part 1: Overview (Parlay 3)".
[10] ETSI TS 123 002: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Network architecture (3GPP TS 23.002)".
[11] ETSI TS 123 278: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Customized Applications for Mobile network Enhanced
Logic (CAMEL) Phase 4; Stage 2; IM CN Interworking (3GPP TS 23.278)".
[12] ETSI TS 129 278: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Customised Applications for Mobile network Enhanced
Logic (CAMEL); CAMEL Application Part (CAP) specification for IP Multimedia Subsystems
(IMS) (3GPP TS 29.278)".
[13] IETF RFC 3136 (2001): "The SPIRITS Architecture".
[14] IETF RFC 3261 (2002): "SIP: Session Initiation Protocol".
[15] ITU-T Recommendation H.248: "Gateway control protocol".
[16] ETSI TS 182 009: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Architecture to support emergency communication from
citizen to authority [Endorsed document 3GPP TS 23.167, Release 7]".
2.2 Informative references
The following referenced documents are not essential to the use of the present document but they assist the user with
regard to a particular subject area. For non-specific references, the latest version of the referenced document (including
any amendments) applies.
Not applicable.
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
IP Multimedia Subsystem: As defined in TS 123 002 [10].
NGN IP Multimedia Subsystem: IMS that supports the provision of SIP-based multimedia services and PSTN/ISDN
simulation services to NGN terminals
User Equipment (UE): one or more devices allowing a user to access services delivered by TISPAN NGN networks
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3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AF Application Function
AS Application Server
ASF Application Server Function
BCSM Basic Call State Model
BGF Border Gateway Function
CAMEL Customized Application for Mobile Enhanced Logic
CCBS Call Control on Busy Subscriber
CSCF Call Session Control Function
E-CSCF Emergency-Call Session Control Function
IBCF Intermediate Breakout Control Function
I-BGF Interconnection-Border Gateway Function
I-CSCF Interrogating-Call Session Control Function
IM-MGW IP Multimedia - Media GateWay
IMS IP Multimedia Subsystem
IN Intelligent Network
INAP IN Application Part
IN-SCF Intelligent Network Switching Control Function
IP-CAN IP-Connectivity Access Network
ISDN Integrated Services Digital Network
MGCF Media Gateway Control Function
MGF Media Gateway Function
MM MultiMedia
MRFC Multimedia Resource Function Controller
MRFP Multimedia Resource Function Processor
NAPT Network Address and Port Translation
NASS Network Attachment SubSystem
NGN Next Generation Network
OSA Open Service Access
P-CSCF Proxy-Call Session Control Function
PDF Policy Decision Function
PES PSTN/ISDN Emulation Subsystem
PSTN Public Switched Telephony Network
RACS Resource and Admission Control Subsystem
SCF Switching Control Function
SCIM Service Capability Interaction Manager
S-CSCF Serving-Call Session Control Function
SGF Signalling Gateway Function
SIP Session Initiation Protocol
SLF Subscription Locator Function
SPIRITS Service in the PSTN/IN Requesting InTernet Services
SSF Service Switching Function
TCAP Transaction Capabilities Application Part
T-MGF Trunking-Media Gateway Function
UE User Equipment
UPSF User Profile Server Function
4 Overall architecture
The TISPAN NGN functional architecture ES 282 001 [1] is structured according to a service layer and an IP-based
transport layer (see figure 1).
The service layer comprises the following components:
• The IP Multimedia Subsystem core component (IMS).
• The PSTN/ISDN Emulation Subsystem (PES).
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User Equipment
SIST ES 282 007 V2.0.0:2008
 9 ETSI ES 282 007 V2.0.0 (2008-05)
• Other multimedia subsystems and applications.
• Common components (i.e. used by several subsystems) such as those required for accessing applications,
charging functions, user profile management, security management, routing data bases (e.g. ENUM), etc.
IP-connectivity is provided to NGN user equipment by the transport layer, under the control of the Network Attachment
SubSystem (NASS) and the Resource and Admission Control Subsystem (RACS). These subsystems hide the transport
technology used in access and core networks below the IP layer.
The present document further describes the functional architecture of the IP Multimedia Subsystem (IMS) core
component.
Applications
Service Layer
Other
Subsyst ems
User
profiles
Core IMS
PSTN/ISDN
Emulat ion
Subsyst em
Transport Layer
Network
Attachment
Resource and
Subsyst em
Admission Control
Subsyst em
Transport processing functions

Figure 1: TISPAN NGN overall architecture
5 Overview
The NGN IP Multimedia Subsystem (IMS) supports the provision of SIP-based multimedia services to NGN terminals.
It also supports the provision of PSTN/ISDN simulation services.
Functional entities of an IMS may be used by an operator in support of transit network scenarios. The routing may be
performed, depending on the entity performing the routing, and depending on the traffic case, on signalling information,
configuration data, and/or data base lookup.
The NGN IMS, also known as "Core IMS" is a subset of the 3GPP IMS defined in TS 123 002 [10] which is restricted
to the session control functionalities. Application Servers (AS) and transport/media related functions such as the
Multimedia Resource Function Processor function (MRFP) and the IP Multimedia Gateway Functions (IM-MGW) are
considered to be outside the "core IMS".
Although essentially identical to the 3GPP IMS entities, NGN IMS functional entities might exhibit minor variations in
behaviour, due to differences in access networks and user equipment. However, the NGN IMS architecture defined in
the present document remains compatible with 3GPP-defined IP-connectivity access networks (IP-CAN) and as such
can provide services to user equipment connected to both fixed broadband access and 3GPP IP-CANs (see annex A).
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Figure 2 illustrates the position of the IMS in the overall NGN architecture. The IMS interfaces the following
components:
• User Equipment.
• The Resource and Admission Control Subsystem.
• The Network Attachment Subsystem.
• The PSTN/ISDN.
• The PSTN/ISDN Emulation Subsystem.
• Other multimedia subsystems.
• Charging Functions.
• Network Management Functions.
• Applications and other common architectural elements.
Charging functions
Network Management
Functions
TISPAN
PSTN/ISDN Emulation
Applications/
Subsystem
Common elements
Other MM
Core
User
Subsystems
IMS
Equipment
PSTN/ISDN
Network Attachment Resource and
Subsystem Admission Control
Subsystem

Figure 2: TISPAN IMS and its environment
6 Functional entities
Figure 3 provides an overview of the functional entities that compose the NGN IMS, the reference points between them
and with components outside the IMS.
Unless stated explicitly, the functional entities identified in this clause are identical to those defined in TS 123 002 [10].
Except when highlighting explicitly a difference, the descriptions provided in the present document are intended to
provide tutorial information only and in case of discrepancy with the definitions in TS 123 002 [10], the definitions in
TS 123 002 [10] shall take precedence.
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Rf/Ro
Charging
Ut
AS
Functions
Sh
Dh
ISC/Ma
UPSF Iw
Rf/Ro
Dx SLF
Cx
IWF
Ib
Network
Attachment Mw
Mx
Ic
Subsystem
I/S-CSCF
IBCF
Mx
«Core IMS» Mk
Mi
BGCF
Mr
e2
Mw
Mj
Mx
Mg
P-CSCF
MGCF
MRFC
Ie
Gq'
Gq'
SGF
Mn
Mp
Gm RACS RACS
MRFP T-MGF
I-BGF
C-BGF
UE
Transport Processing Functions (Access and Core)

Figure 3: NGN IMS overview
6.1 Call Session Control Function (CSCF)
The Call Session Control Function (CSCF) establishes, monitors, supports and releases multimedia sessions and
manages the user's service interactions. For more details see clause 4a.7.1 in TS 123 002 [10].
NOTE: The CSCF can act as Proxy CSCF (P-CSCF), Serving CSCF (S-CSCF) or Interrogating CSCF (I-CSCF).
The P-CSCF is the first contact point for the UE within the IM subsystem (IMS); the S-CSCF actually
handles the session states in the network; the I-CSCF is mainly the contact point within an operator's
network for all IMS connections destined to a subscriber of that network operator, or a roaming
subscriber currently located within that network operator's service area.
This functional entity is identical to the CSCF defined in TS 123 002 [10], except for when acting as a P-CSCF. The
P-CSCF behaviour differs from the behaviour in TS 123 002 [10] by the following main points:
• The e2 reference point is supported to enable the P-CSCF to retrieve information (e.g. physical location of the
user equipment) from the Network Attachment Subsystem (see clause 11).
• The Gq and Iq reference points are not supported but replaced with the Gq' reference point (see clause 12).
Based on local configuration, the I-CSCF may perform transit routing functions (see TS 182 006 [2]).
Further specifications of the P-, S- and I-CSCF are provided in TS 182 006 [2].
Support of emergency communications require the use of an E-CSCF as described in TS 182 009 [16]. For the sake of
simplicity this type of CSCF is not represented on figure 3.
6.2 Media Gateway Control Function (MGCF)
The Media Gateway Controller Function (MGCF) provides the ability to control a trunking media gateway function
(T-MGF) through a standardized interface. Such control includes allocation and deallocation of resources of the media
gateway, as well as modification of the usage of these resources. The MGCF communicates with the CSCF, the BGCF
and circuit-switched networks. The MGCF performs protocol conversion between ISUP and SIP. It also supports
interworking between SIP and non-call related SS7 signalling (i.e. TCAP-based signalling for supplementary services
such as CCBS).
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In case of incoming calls from legacy networks, the MGCF determines the next hop in IP routing depending on
received signalling information.
Based on local configuration, the MGCF may perform transit routing functions (see TS 182 006 [2]).
This functional entity is identical to the MGCF defined in TS 123 002 [10], except that in addition it supports TCAP
interworking. A node implementing this functional entity in an NGN network and a node implementing it in a 3GPP
network may differ in terms of supported resources (e.g. codecs) and configuration.
6.3 Multimedia Resource Function Controller (MRFC)
The Multimedia Resource Function Controller (MRFC), in conjunction with an MRFP located in the transport layer
(see ES 282 001 [1]), provides a set of resources within the core network for supporting services. The MRFC interprets
information coming from an AS via an S-CSCF and control MRFP accordingly. The MRFC, in conjunction with the
MRFP, provides e.g. multi-way conference bridges, announcement playback, media transcoding, etc.
This functional entity is identical to the MRFC defined in TS 123 002 [10], although a node implementing this
functional entity in an NGN network and a node implementing it in a 3GPP network may differ in terms of supported
resources and configuration.
6.4 Breakout Gateway Control Function (BGCF)
The Breakout Gateway Control Function (BGCF) determines the next hop in SIP routing. This determination may be
based on information received in the protocol, administrative information, and/or database access. For PSTN
terminations, the BGCF selects the network in which PSTN breakout is to occur and - within the network where the
breakout is to occur - selects the MGCF. This functional entity is identical to the BGCF defined in TS 123 002 [10],
although a node implementing this functional entity in an NGN network and a node implementing it in a 3GPP network
may differ in terms of configuration (e.g. breakout criteria).
In case of transit the BGCF may have extra functionality for routing transit traffic (see TS 182 006 [2]).
6.5 Interconnection Border Control Function (IBCF)
An IBCF provides application specific functions at the SIP/SDP protocol layer in order to perform interconnection
between two operator domains. It enables communication between IPv6 and IPv4 SIP applications. network topology
hiding, controlling transport plane functions, screening of SIP signalling information, selecting the appropriate
signalling interconnect and generation of charging data records.
Based on local configuration, the IBCF may perform transit routing functions (see TS 182 006 [2]).
This functional entity is identical to the IBCF defined in TS 123 002 [10].
Details are described in TS 182 006 [2].
7 Internal reference points
Unless stated explicitly, the reference points identified in this clause are identical to those defined in TS 123 002 [10].
Except when highlighting explicitly a difference, the descriptions provided in the present document
...