ETSI TS 182 025 V3.3.1 (2011-03)

Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); Business trunking; Architecture and functional description

RTS/TISPAN-02080-NGN-R3

General Information

• Status: Published
• Publication Date: 30-Mar-2011
• Technical Committee: TISPAN 2 - TISPAN Architecture
• Current Stage: 12 - Completion
• Due Date: 30-Mar-2011
• Completion Date: 31-Mar-2011

Standards Content (Sample)

Technical Specification
Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
Business trunking;
Architecture and functional description

2 ETSI TS 182 025 V3.3.1 (2011-03)

Reference
RTS/TISPAN-02080-NGN-R3
Keywords
architecture, functional, trunking
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: [phone]  Fax: [phone]

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 2011.
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.
LTE™ is a Trade Mark of ETSI currently being registered
for the benefit of its Members and of the 3GPP Organizational Partners.
GSM® and the GSM logo are Trade Marks registered and owned by the GSM Association.
ETSI
3 ETSI TS 182 025 V3.3.1 (2011-03)
Contents
Intellectual Property Rights . 6
Foreword . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 9
3 Definitions and abbreviations . 9
3.1 Definitions . 9
3.2 Abbreviations . 9
4 Overview . . 10
4.1 General principles. 10
4.2 Access network interconnection . 10
4.3 Service level layer interconnection . 11
5 Functional architecture . 11
5.1 General . 11
5.2 Subscription based business trunking . 12
5.2.1 General . 12
5.2.2 Used functional entities at the service layer . 12
5.2.3 Used reference points at the service layer . 12
5.2.4 Used functional entities at the transport layer . 12
5.2.5 Used reference points at the transport layer . 13
5.3 Peering-based business trunking . 13
5.3.1 General . 13
5.3.2 Used functional entities at the service layer . 14
5.3.3 Used reference points at the service layer . 14
5.3.4 Used functional entities at the transport layer . 15
5.3.5 Used reference points at the transport layer . 15
5.4 Session-level virtual leased line . 15
5.4.1 General . 15
5.4.2 Used functional entities at the service layer . 15
5.4.3 Used reference points at the service layer . 16
5.4.4 Used functional entities at the transport layer . 16
5.4.5 Used reference points at the transport layer . 16
5.5 Support for roaming NGCN user . 16
5.5.1 General . 16
5.5.2 Used functional entities at the service layer . 16
5.5.3 Used reference points at the service layer . 17
5.5.4 Used functional entities at the transport layer . 17
5.5.5 Used reference points at the transport layer . 17
5.6 Support for roaming NGN user . 17
6 Procedures . 17
6.1 Subscription based business trunking . 17
6.1.1 Introduction. 17
6.1.2 Identification . 18
6.1.3 Registration . 18
6.1.4 Requests originating from an NGCN user entering NGN. 19
6.1.4.1 General . 19
6.1.4.2 NGCN not considered as privileged sender and not trusted by NGN . 19
6.1.4.3 NGCN considered as privileged sender and trusted by NGN . 20
6.1.4.4 NGCN considered as privileged sender and not trusted by NGN . 21
6.1.5 Requests terminating to an NGCN user leaving NGN . 21
6.1.5.1 General . 21
6.1.5.2 NGCN not considered as privileged sender and not trusted by NGN . 23
ETSI
4 ETSI TS 182 025 V3.3.1 (2011-03)
6.1.5.3 NGCN considered as privileged sender and trusted by NGN . 23
6.1.5.4 NGCN considered as privileged sender and not trusted by NGN . 23
6.1.6 Business trunking applications . 23
6.1.6.1 General . 23
6.1.6.2 Routeing capabilities . 24
6.1.6.2.1 Overview . 24
6.1.6.2.2 Break-in . 24
6.1.6.2.3 Break-out . 24
6.1.6.2.4 Bulk rerouting . 24
6.1.6.3 Communication admission control . 24
6.1.6.4 Anonymous communication rejection. 24
6.1.6.5 Communication barring . 25
6.1.7 Signalling transparency . 25
6.1.8 Involvement of functions on the media path . 25
6.1.8.1 General . 25
6.1.8.2 DTMF . 25
6.1.8.3 Codecs . 25
6.1.9 Handling of the P-Access-Network-Info header . 26
6.1.10 Emergency calls . 26
6.1.11 Charging . 26
6.1.12 Advice of Charge . 26
6.1.13 NAT traversal . 27
6.1.14 Private network traffic . 27
6.1.15 P-CSCF and IP-CAN redundancy . 27
6.2 Peering-based business trunking . 28
6.2.1 Introduction. 28
6.2.2 Identification . 28
6.2.3 Registration . 28
6.2.4 Requests originating from an NGCN user entering NGN. 28
6.2.4.1 General . 28
6.2.4.2 NGCN not trusted by NGN . 29
6.2.4.3 NGCN trusted by NGN . 29
6.2.5 Requests terminating to an NGCN user leaving NGN . 29
6.2.5.1 General . 29
6.2.5.2 NGCN not trusted by NGN . 30
6.2.5.3 NGCN trusted by NGN . 30
6.2.6 Business trunking application . 30
6.2.6.1 General . 30
6.2.6.2 Routeing related business trunking applications . 30
6.2.6.3 Communication admission control . 30
6.2.6.4 Anonymous communication rejection. 30
6.2.6.5 Communication barring . 30
6.2.7 Signalling transparency . 31
6.2.8 Involvement of functions on the media path . 31
6.2.9 Handling of the P-Access-Network-Info header . 31
6.2.10 Emergency calls . 31
6.2.11 Charging . 31
6.2.12 Advice of Charge . 31
6.2.13 NAT traversal . 32
6.2.14 Private network traffic . 32
6.3 Session-level virtual leased line between NGCN sites . 32
6.3.1 Introduction. 32
6.3.2 Identification . 32
6.3.3 Registration . 32
6.3.4 Session originating from a NGCN user entering NGN . 32
6.3.4.1 General . 32
6.3.4.2 NGCN not trusted by NGN . 32
6.3.4.3 NGCN trusted by NGN . 32
6.3.5 Session terminating to an NGCN user leaving NGN . 33
6.3.5.1 General . 33
6.3.5.2 NGCN not trusted by NGN . 33
6.3.5.3 NGCN trusted by NGN . 33
ETSI
5 ETSI TS 182 025 V3.3.1 (2011-03)
6.3.6 Business trunking applications . 33
6.3.7 Signalling transparency . 33
6.3.8 Involvement of functions on the media path . 33
6.3.9 Handing of the P-Access-Network-Info header . 33
6.3.10 Emergency calls . 33
6.3.11 Charging . 33
6.3.12 Advice of Charge . 33
6.3.13 NAT traversal . 34
6.3.14 Private network traffic . 34
6.4 NGCN user roaming into NGN public network . 34
6.4.1 Introduction. 34
6.4.2 Identification . 34
6.4.3 Registration . 34
6.4.4 Requests originating from an NGCN user roaming in NGN . 34
6.4.5 Requests terminating on an NGCN user roaming in NGN . 35
6.4.6 Business trunking applications . 35
6.4.7 Signalling transparency . 35
6.4.8 Involvement of functions on the media path . 35
6.4.9 Handing of the P-Access-Network-Info header . 35
6.4.10 Emergency calls . 35
6.4.11 Charging . 35
6.4.12 Advice of Charge . 35
6.4.13 NAT traversal . 35
6.4.14 Private network traffic . 35
7 Use of transport functions . 36
7.1 Use of transport control sublayer . 36
7.1.1 Use of NASS. 36
7.1.2 Use of RACS . 36
7.2 Use of transport processing functions . 36
8 Security. 36
9 Management . 36
Annex A (informative): Example signalling flows of business trunking and roaming
arrangements . 37
A.1 Scope of signalling flows . 37
A.2 Introduction . 37
A.3 Signalling flows for registration . 37
A.3.1 Introduction . 37
A.3.2 Registration of a roaming NGCN UE visiting an NGN/IMS with which the NGCN has a direct roaming
agreement . 37
A.3.2.1 General . 37
A.3.2.2 Signalling flow for registration of a roaming NGCN UE visiting an NGN/IMS with which the
NGCN has a direct roaming agreement . 38
A.3.2.3 Overview of routing decisions . 44
A.4 Signalling flows for call origination . 45
A.5 Signalling flows for call termination . 45
Annex B (informative): Service Level Agreement (SLA) considerations . 46
Annex C (informative): Topics for business trunking for a future release . 47
Annex D (informative): Bibliography . 48
Annex E (informative): Change history . 49
History . 50

ETSI
6 ETSI TS 182 025 V3.3.1 (2011-03)
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 Technical Specification (TS) has been produced by ETSI Technical Committee Telecommunications and Internet
converged Services and Protocols for Advanced Networking (TISPAN).
ETSI
7 ETSI TS 182 025 V3.3.1 (2011-03)
1 Scope
The present document provides architecture and functional requirements for business trunking for the Next Generation
Network.
The present document also specifies the protocol requirements for the NGCN to attach to the NGN (in particular the IM
CN subsystem) and also any protocol requirements relation to application servers provided in support of business
trunking.
Business trunking is a set of NGN capabilities that may be applied to communications between Next Generation
Corporate Networks (NGCN) using the NGN as a transit.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
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 necessary for the application of the present document.
[1] ETSI TS 181 019: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Business Communication Requirements".
[2] ETSI ES 282 001: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Functional Architecture".
[3] ETSI ES 282 004: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Functional Architecture; Network Attachment
Sub-System (NASS)".
[4] ETSI ES 282 007: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN);IP Multimedia Subsystem (IMS);Functional architecture".
[5] Void.
[6] ETSI ES 282 010: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Charging management [Endorsement of 3GPP TS 32.240
Release 7, 3GPP TS 32.260 Release 7, 3GPP TS 32.297 Release 7, 3GPP TS 32.298 Release 7 and
3GPP TS 32.299 Release 7, modified]".
[7] ETSI TS 182 023: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Core and enterprise NGN interaction scenarios; Architecture
and functional description".
[8] ETSI TS 183 011: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); PSTN/ISDN simulation services: Anonymous Communication
Rejection (ACR) and Communication Barring (CB); Protocol specification".
[9] ETSI TS 183 019: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Network Attachment; User-Network Interface Protocol
Definitions".
ETSI
8 ETSI TS 182 025 V3.3.1 (2011-03)
[10] ETSI TS 124 628: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; Common Basic Communication procedures using IP
Multimedia (IM) Core Network (CN) subsystem; Protocol specification (3GPP TS 24.628)".
[11] ETSI ES 283 035: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Network Attachment Sub-System (NASS); e2 interface based
on the DIAMETER protocol".
[12] ETSI TS 124 647: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; Advice Of Charge (AOC) using IP Multimedia (IM)
Core Network (CN) subsystem (3GPP TS 24.647)".
[13] ETSI TS 129 658: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; TISPAN; SIP Transfer of IP Multimedia Service
Tariff Information; Protocol specification (3GPP TS 29.658)".
[14] ETSI TS 183 065: "Telecommunications and Internet converged Services and Protocols for
Advanced Networks (TISPAN); Customer Network Gateway Configuration Function; e3 Interface
based upon CWMP".
[15] ETSI TS 185 003: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Customer Network Gateway (CNG) Architecture and
Reference Points".
[16] ETSI TS 187 003: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Security; Security Architecture".
[17] ETSI TS 123 228: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; IP Multimedia Subsystem (IMS); Stage 2
(3GPP TS 23.228)".
[18] ETSI TS 124 229: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; IP multimedia call control protocol based on Session
Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3
(3GPP TS 24.229 Release 9)".
[19] ETSI TS 133 203: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; 3G security; Access security for IP-based services
(3GPP TS 33.203)".
[20] ECMA TR/96: "Next Generation Corporate Networks (NGCN) - Identification and Routing".
[21] IETF RFC 3261 (2002): "SIP: Session Initiation Protocol".
[22] IETF RFC 3324 (2002): "Short Term Requirements for Network Asserted Identity".
[23] Void.
[24] IETF RFC 5031 (2008): "A Uniform Resource Name (URN) for Emergency and Other
Well-Known Services".
[25] IETF RFC 3263 (2002): "Session Initiation Protocol (SIP): Locating SIP Servers".
[26] IETF RFC 4733 (2006): "RTP Payload for DTMF Digits, Telephony Tones, and Telephony
Signals".
[27] ETSI TS 181 005 (V3.3.1): "Telecommunications and Internet converged Services and Protocols
for Advanced Networking (TISPAN); Service and Capability Requirements".
[28] ITU-T Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice frequencies".
[29] IETF RFC 5626 (2009): "Managing Client-Initiated Connections in the Session Initiation Protocol
(SIP)".
ETSI
9 ETSI TS 182 025 V3.3.1 (2011-03)
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] draft-ietf-sipcore-location-conveyance-02 (2010): "Session Initiation Protocol Location
Conveyance".
[i.2] draft-vanelburg-dispatch-private-network-ind-00 (2009): "Requirements for explicit private
network indication".
[i.3] ETSI TS 123 003: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Numbering, addressing and identification
(3GPP TS 23.003)".
[i.4] ETSI TS 123 218: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; IP Multimedia (IM) session handling; IM call model;
Stage 2 (3GPP TS 23.218)".
[i.5] ETSI TR 183 069: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Business Trunking; NGCN-NGN Interfaces Implementation
Guide".
[i.6] ETSI TS 129 165: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; Inter-IMS Network to Network Interface (NNI)
(3GPP TS 29.165)".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TS 181 019 [1], ES 282 004 [3],
TS 123 228 [17], TS 123 003 [i.3] and TS 123 218 [i.4] apply.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AOR Address Of Record
AS Application Server
B2BUA Back-to-Back User Agent
CNG Customer Network Gateway
CNGCF Customer Network Gateway Control Function
CSCF Call Session Control Function
DNS Domain Name System
DSL Digital Subscriber Line
I-CSCF Interrogating CSCF
IP Internet Protocol
IP-CAN IP Connectivity Access Network
LAN Local Area Network
NASS Network Attachment SubSystem
NGCN Next Generation Corporate Network
NGN Next Generation Network
P-CSCF Proxy CSCF
S-CSCF Serving-CSCF
SIP Session Initiation Protocol
SLA Service Level Agreement
UE User Equipment
UPSF User Profile Server Function
ETSI
IP Edge
Access Node
10 ETSI TS 182 025 V3.3.1 (2011-03)
URI Uniform Resource Identifier
4 Overview
4.1 General principles
Business trunking refers to an architecture where corporate networks appear to the NGN as an NGCN. Although the
interface between an NGCN and an NGN is IP-based, this does not preclude the existence of non-IP-based elements
within the NGCN but not visible to the NGN. The NGCN appears to the NGN as a black box.
4.2 Access network interconnection
NGCN sites may be connected to any IP-CAN valid for TISPAN NGN using a Customer Network Gateway (CNG), as
defined in ES 282 001 [2] or connected to an NGN core network via an edge router of the enterprise.
Connection to an IP-CAN includes the case where the NGCN site incorporates a CNG as defined in TS 185 003 [15],
connected to a DSL-based access network (figure 4.1) as well as the case where the NGCN site comprises a corporate
LAN with one or more edge routers playing the role of a CNG connected to access nodes in the operator's access
network (figure 4.2).
NOTE 1: Use of the "SIP Proxy/B2BUA" function within the CNG, as defined in TS 185 003 [15], is not
applicable to the present release of the present document.
NOTE 2: Within an NGCN site, the CNG functionality may be collocated with an NGCN host or a stand-alone
equipment unit.
Towards an access network, the NGCN site acts as a UE. For further details see clause 7.
Towards the IM CN subsystem, the entry point / exit point entity is dependent on the approach adopted and is described
further in clause 6.
An NGCN connects a multiplicity of endpoints to the network, each of which may be an IP device or a legacy phone.
The NGN does not need to have any knowledge on the individual endpoints connected to the NGCN.
With the subscription based approach, for each NGCN site, the UPSF stores a single public user identity and a single
associated user profile enabling triggering of network-based services beyond those provided by the NGCN itself. A set
of telephone numbers and/or SIP URIs are also associated with each NGCN site. The former could be expressed in the
form of number ranges and the latter using wildcards in the user or host part.
Di
Aggregation
CNG
NGCN hosts/PBX
DSL access Segment
NGCN site / User Equipement
Operator's Domain
Figure 4.1: DSL access
ETSI
IP Edge
Access Node
11 ETSI TS 182 025 V3.3.1 (2011-03)
NGCN hosts/PBX
Aggregation Di
CNG
LAN Access Segment
NGCN Site / User Equipment Operator's domain

Figure 4.2: Corporate LAN access
Identifiers based on private numbers shall be handled in accordance with ECMA TR/96 [20].
4.3 Service level layer interconnection
The service level layer interconnection makes use of IMS. Two main interconnection arrangements are provided:
• Interconnection of the NGN and NGCN where the entry point to the IMS is the P-CSCF. This is known as the
subscription-based approach. This is represented by scenario 5 in clause 8.3 of TS 182 023 [7]. In this case
each site of the NGCN has a service subscription to the IMS, with an appropriate entry in the UPSF. An AS is
used to provide business trunking applications, e.g. those defined in TS 181 019 [1], clause 4.4. If such
capabilities are not required, then the AS is not included in any request processing. The service level
capabilities of this scenario are described further in clause 6.1.
• Interconnection of the NGN and NGCN where the entry point to the IMS is the IBCF. This is known as the
peering-based approach. This is represented by scenario 6 in clause 8.4 of TS 182 023 [7]. In this case there is
no dynamic registration to the IMS of individual NGCN-users or NGCN-sites. However, the absence of such
dynamic registrations in a UPSF does not preclude the NGN to host enterprise specific data in a UPSF. The
service level capabilities of this scenario are described further in clause 6.2.
The second of these arrangements is called the peering-based approach due to the similarity of the arrangement to the
mechanism by which the IMS in two NGNs interconnect. The provision of the business trunking applications (e.g. those
defined in TS 181 019 [1], clause 4.4) is realized by an intelligent routeing function, which may involve an AS
depending on the actual enterprise specific data.
In none of the arrangements do the private extensions behind the NGCN need their own service subscription within the
NGN, since they are owned and managed by the NGCN. The private extensions register with the NGCN, and the
NGCN provides the individual services to the private extensions.
An architecturally similar case to the peering-based approach is represented by scenario 3 in clause 7.1 of
TS 182 023 [7]. In this case, SIP requests at one entry point are always routed to the same exit point, and no business
trunking applications are provided. The service level capabilities of this scenario are described further in clause 6.3 of
the present document. This scenario carries private network traffic only.
5 Functional architecture
5.1 General
The architectural split of the service layer and transport layer (used in the description below) is defined in
ES 282 001 [2].
ETSI
Corporate LAN
12 ETSI TS 182 025 V3.3.1 (2011-03)
5.2 Subscription based business trunking
5.2.1 General
This describes the architectural requirements for the connection of a Next Generation Corporate Network site (NGCN
site) to the NGN using the P-CSCF as an entry point at the service layer.
Clause 8.3 of TS 182 023 [7] shows the arrangement of the involved functional entities.
5.2.2 Used functional entities at the service layer
The main functional entities from the IMS service layer as specified in ES 282 007 [4] that are used to realise
subscription-based business trunking arrangements are as follows:
• P-CSCF;
• S-CSCF;
• AS (in case a business trunking application is required);
• UPSF.
NOTE: The above list includes only those entities where specific functionality is applied to realise business
communication in this scenario. Entities which otherwise transport, but apply no special processing,
e.g. I-CSCF, are not listed.
A description of specific procedures executed to provide subscription-based business trunking can be found in
clause 6.1.
5.2.3 Used reference points at the service layer
The main reference points from the IMS service layer as specified in ES 282 007 [4] that are used to realise
subscription-based business trunking arrangements are as follows:
• Gm (this reference point forms the point of interconnection between the NGCN site and the NGN at the
service layer);
• Mw;
• Cx;
• ISC (in case a business trunking application is required);
• Sh (in case a business trunking application is required);
• e2;
• Gq'.
NOTE: The above list includes only those interfaces where specific protocol is applied to realise business
communicatio
...