ETSI TS 184 006 V2.1.1 (2008-09)

ETSI TS 184 006 V2.1.1 (2008-09)
Technical Specification


Telecommunications and Internet converged Services and
Protocols for Advanced Networking (TISPAN);
Interconnection and Routeing requirements related to
Numbering and Naming for NGNs;
NAR Interconnect

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2 ETSI TS 184 006 V2.1.1 (2008-09)



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ETSI

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3 ETSI TS 184 006 V2.1.1 (2008-09)
Contents
Intellectual Property Rights . 4
Foreword . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 6
3 Abbreviations . 7
4 Introduction . 7
5 Routeing Model for NGN Interconnection. 8
5.1 Reference scheme for interconnection . 8
5.2 Interconnection and Routeing. 8
5.3 Transit capabilities . 9
5.4 Example of complete set of CP's roles . 10
5.5 Routeing process requirements and related CP roles . 11
5.6 SIP and E.164 numbering . 12
5.7 Address Resolution, Routeing requirements . 13
5.7.1 tel URI and SIP URI resolution requirements and procedures . 15
5.8 Relation with NAR Interconnection general framework . 17
6 Interconnection, interworking, interface and routeing requirements . 17
6.1 Interconnection NNI in IMS and NGN architecture . 18
6.2 Transit network scenarios . 19
6.3 Application to different NGN scenarios . 21
Annex A (informative): Protocols at the NNI points and interworking . 22
Annex B (informative): SIP Header Fields at the NNI relevant to routing and identification. 24
History . 27

ETSI

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4 ETSI TS 184 006 V2.1.1 (2008-09)
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

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5 ETSI TS 184 006 V2.1.1 (2008-09)
1 Scope
The present document analyzes the issues concerned with interconnection and routeing in NGN and their implications
and requirements for numbering, naming and addressing and related resolution functionalities.
Several different interconnection scenarios are considered, based on TISPAN "NGN Functional Architecture" ([5]),
although not all require the use of all architectural functions. The role of the transit network has also been considered in
order to evaluate the knowledge of numbers/names served by different operators and related requirements for routing
purposes.
Some scenarios may require the availability of infrastructure systems for numbering/naming resolutions, such as
infrastructure ENUM, or other database based system for route resolution, and may require coordinated provision by
involved operators.
The present document focuses on calls routed between subscribers identified by E.164 numbers, coded through either
tel URI and SIP URI formats. It also applies only to the transfer of calls across interconnection points between the home
network of the A-Party and the home network of the B-Party. It does not consider in detail interconnections needed to
support roaming scenarios. A further issue of the present document will consider interconnect scenarios related to
roaming.
The present document is relevant not just to IMS but to any NGN SIP-based interconnection.
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] Void.
[2] ETSI TS 181 005: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Services and Capabilities Requirements".
ETSI

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6 ETSI TS 184 006 V2.1.1 (2008-09)
[3] ETSI TS 182 012: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IMS-based PSTN/ISDN Emulation Sub-system (PES);
Functional architecture".
[4] ETSI ES 282 007: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Subsystem (IMS); Functional architecture".
[5] ETSI ES 282 001: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Functional Architecture".
[6] ETSI ES 283 018: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Resource and Admission Control: H.248 Profile for controlling
Border Gateway Functions (BGF) in the Resource and Admission Control Subsystem (RACS);
Protocol specification".
[7] ETSI ES 283 003: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); IP Multimedia Call Control Protocol based on Session
Initiation Protocol (SIP) and Session Description Protocol (SDP) Stage 3 [3GPP TS 24.229
[Release 7], modified]".
[8] ETSI TS 123 228: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); IP Multimedia Subsystem (IMS); Stage 2 (3GPP TS
23.228 version 7.5.0 Release 7)".
[9] ITU-T Recommendation Q.3401: "NGN NNI Signalling Profile (Protocol Set 1)".
[10] ETSI EN 383 001: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Interworking between Session Initiation Protocol (SIP) and
Bearer Independent Call Control (BICC) Protocol or ISDN User Part (ISUP) [ITU-T
Recommendation Q.1912.5, modified]".
[11] ETSI TS 123 228: "IP Multimedia Subsystem (IMS); Stage 2".
[12] ETSI TS 124 228: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Signalling flows for the IP multimedia call control based
on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3
(3GPP TS 24.228 Release 5)".
[13] ETSI TS 124 229: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Internet Protocol (IP) multimedia call control protocol
based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3
(3GPP TS 24.229 Release 8)".
[14] ETSI TS 129 163: "Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); Interworking between the IP Multimedia (IM) Core
Network (CN) subsystem and Circuit Switched (CS) networks (3GPP TS 29.163 Release 7)".
[15] ETSI TS 184 002: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Identifiers (IDs) for NGN".
[16] Void.
[17] ITU-T Recommendation E.164: "The international public telecommunication numbering plan".
[18] IETF RFC 3261: "SIP: Session Initiation Protocol".
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.
[i.1] ETSI TR 180 000: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); NGN Terminology".
ETSI

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7 ETSI TS 184 006 V2.1.1 (2008-09)
[i.2] ETSI TR 184 007: "Telecommunications and Internet converged Services and Protocols for
Advanced Networking (TISPAN); Naming/Numbering Address Resolution (NAR)".
3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GPP 3rd Generation Partnership Project
BGCF Breakout Gateway Control Function
BICC Bearer-Independent Call Control
CP Communication Provider
DNS Domain Name System
ENUM E.164 telephone NUmber Mapping
GRX GRPS Roaming eXchange
GSMA GSM Association
IBCF Interconnection Border Control Function
I-CSCF Interrogating-Call/Session Control Function
I-ENUM Infrastructure ENUM
IETF Internet Engineering Task Force
IMS IP Multimedia System
IPX IP Packet eXchange
ISUP ISDN Signalling User Part
IWF InterWorking Function
MGCF Media Gateway Control Function
NAR Naming/Numbering Addressing Resolution
NGN Next generation Network
NNI Network to Network Interface
OPID Originating Party IDentity
P-CSCF Proxy-Call/Session Control Function
PES PSTN Emulation Service
PSTN Public Switched Telephone Network
RACS Resource and Admission Control Subsystem
S-CSCF Serving-Call/Session Control Function
SDP Session Description Protocol
SIP Session Initiation Protocol
TPID Terminating Party IDentity
UA User Agent
URI Uniform Resource Identifier
4 Introduction
This Technical Specification:
• Defines a Routeing Model for NGN Interconnection.
• Proposes the first set of Requirements and related CP Routeing Roles.
• Defines the resolution process for tel URI and SIP URI.
• Proposes the possible basic structure of NAR [i.2] Interconnect Framework.
ETSI

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8 ETSI TS 184 006 V2.1.1 (2008-09)
5 Routeing Model for NGN Interconnection
5.1 Reference scheme for interconnection
Figure 1 describes the NGN layers and the reference scheme for interconnection in NGN. The routeing resolution in
NGN includes both the typical IP interworking routeing rules that are bounded into the transport layer and the
service/control layer ones.

Network A Network B
E.164 number
Service/Control Service/Control
Signalling
Layer Layer
Transport Layer Transport Layer
NNI
NTP
NTP
IP address

Figure 1: Reference scheme for Interconnection and routeing
The call control and service control functions take into account service capabilities requirements for routeing. Some
applications entities (for instance redirect servers and/or location application) may also be required to define the route.
For the purpose of interconnection the Call Control function has to resolve routeing in order to get the next hop and
reach the required destination (the transport layer has to allocate the resource required based on the services
characteristics). As a consequence, the NGN routeing determination process includes both service and transport
functions to define the correct destination and requires an appropriate service transport resources allocation at the
interconnection level.
The functionalities used for routeing at the transport layer follow the existing IP intrinsic routeing mechanisms, and
have also to satisfy the NGN service requirements and the transport resource requirements (RACS function [4], [5]).
Therefore routeing resolution at transport layer is outside the scope of the present document.
The destination number/name and the type of service required are essential to identify the route for service layer
routeing. The ETSI standards on NGN public identity [15] state that E.164 numbering is the main customer
identification scheme. However in addition domain name based identifiers can be also used.
In the case of the SIP protocol, as defined in relevant ETSI standards ([7]), such public identifiers are carried through
so-called SIP URI (i.e. SIP URI: @) and tel URI (i.e. tel URI: number>).
Public identifiers resolution is an essential part of the routeing process to determine the next hop network entity for the
session setup: this entity can either be identified by an intermediate URI translated into an appropriate IP address using
DNS functionality, or directly mapped to an IP address.
5.2 Interconnection and Routeing
The innovative approach for NGN routeing requires identifying a common routeing model that guarantees
interoperability between networks; besides more networks, provided by different operators, can be involved in session
setup and routeing process and related decisions depends on its specific role within the session setup process
(i.e. originating, transit, triggering, termination or interworking).
The routeing model for interconnection should take in account required type of service and existing interconnection
bilateral agreements in order to resolve the route.
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9 ETSI TS 184 006 V2.1.1 (2008-09)
Triggering
CC
Originating/Access
Terminating
Triggering
Role
CC CC
Originating
Terminating
Role
Role
User A User B

Figure 2: Functional framework for routeing and CP roles
Figure 2 identifies the essential Communication Providers' (CP) routeing roles for the routeing process of a generic
session setup established for two users. The user A sends a service request to the NGN call control of the originating CP
that has the objectives of processing the request and putting through the communication to other CPs or/and the user B.
An individual CP may assume different roles on defining the route of the session for a service request and it can apply
particular routeing procedures related also to the knowledge of the service required and the partial or full information on
the final destination to reach (i.e. external routeing).
The same representation can be also be adopted to include the cases where the same CP fulfils all the routeing roles for
an internal call/session started and terminated on the same CP's domain/domains (i.e. internal routeing).
The CP can implement one or more routeing roles at the same time, and can also provide these capabilities for other
CPs (e.g. in the case of hosting).
A description of the basic routeing roles follows:
• Originating Role: responsible for the communication service offered to the end customer and basic service
request and related call/session handling. It is influenced by the Originating customer profile.
• Triggering Role: Responsible for numbering resolution, routeing determination toward final destination and
the choice of appropriate next hop entity (internal or external) to reach it; additionally it is in charge to identify
specific interworking requirements for NGN (IMS or not IMS networks) or for PSTN/ISDN interoperability.
• The numbering resolution process implies the determination of "routable SIP URI" that includes the domain
associated to operator which called user is subscribed to. In the case of terminating calls toward legacy
networks (i.e. PSTN/ISDN or PLMN) the numbering resolution output can be a tel URI.
• Terminating Role: responsible for terminating and serving the session-oriented communication to end user.
5.3 Transit capabilities
In addition to the previous basic CPs' roles the case where one or more transit networks are involved is relevant.
• Transit Role: Route the session-oriented communication request to the next hop CP without any SIP URI or
tel URI mapping in routable SIP URI. All the session related information is carried on to next hop
transparently.
The routeing process for transit is limited to transparently deliver the session setup to the appropriate next hop CP
(without numbering resolution or mapping in a routable SIP URI). However the transit routeing process has to
guarantee appropriate transport resources allocation to preserve service requirements.
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10 ETSI TS 184 006 V2.1.1 (2008-09)
5.4 Example of complete set of CP's roles
Figure 3 points out an example of a complete set of CP's roles for SoIx Interconnection (see SoIx in the NGN
Architecture [5]) that highlights different application of routeing model for route determination.

CP3
CP4
CP2



Transit
Triggering
Role
Role
Transit
Role
CP6


CP5
CP1
Triggering
Originating

Role for
Role
Interworking
Terminating
Role
UE A
UE B
CP7
PSTN/ ISDN
Other “IP Network”
Signalling Control functionalities


Service/Control layer signalling
UE C
Transport layer

Figure 3: CPs roles for routeing process for SoIx interconnection
Following is the routeing process implementation among different CPs, and the description of guidelines for
implementations:
• Originating role, on the basis of service required by session-based originated by Originating user, forwards the
session setup request for routeing analysis to the Triggering Role entity, which is provided internally or by a
different CP on the basis of bilateral agreements.
• Triggering role is per definition responsible for resolving public user identities to determine the next hop
outbound route towards the operator to which the destination user is subscribed.
• Transit role is assumed by a CP that, on the basis of bilateral agreements, transparently forwards the session
setup request to the appropriate next hop CP.
• Terminating role is responsible for delivering communication service session setup to the destination end user;
the numbering/naming analysis and related routeing process is limited to internal identification of session
control entity associated to end user for required service communication session setup and then to
determination of the IP address associated to the user terminal equipment. Where a Routable SIP URI is used,
the CP with the terminating role for a service communication session is identified through the domain part of
the routable SIP URI.
ETSI

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11 ETSI TS 184 006 V2.1.1 (2008-09)
5.5 Routeing process requirements and related CP roles
At least the following parameters and functional elements shall be available as input of NGN Routeing Model
(see figure 4):
• Service parameters: set of parameters that represents service requirement for a specific session setup.
• Terminating Party Identity (TPID): it is an E.164 number in tel URI or SIP URI coding format; optionally a
domain name identifier can be also used.
• Originating Party Identity (OPID): is an E.164 number in tel URI or SIP URI coding format; optionally a
domain name identifier can be also used.
• Performance parameters: That parameter can be taken into account for defining special action on routeing
(i.e. bearer resources allocation, requirements on possible route, congestion and/or unavailable resources, etc.).
It is also relevant to include the case of route determination for the case of overlap signalling (see [7]) in which a partial
routeing decision can be made before dialling is completed.
At least the following parameters and functional elements shall be available as output of NGN Routeing Model (see
figure 4):
• SIP URI or tel URI identifying the destination user.
• Next Hop ID: it identifies the network entity (i.e. border gateway or other signalling/control functionality) that
enables or is in charge of reaching next hop CP.
• Transport resource parameters: parameters meaningful for transport addressing and routeing process at
transport layer for resource allocation.
The SIP URI that it is obtained through the numbering/naming resolution process is called a routable SIP URI since its
domain part identifies the appropriate terminating CP.

Service/Application
Service profile parameter
If internal routeing:
Next Hop control functional entity/Node
(naming or IP addressing)
Common input:
Bearer/media service requirements
OPID
Routing policy (i.e. load sharing, etc.)
TPID OPID
Bearer/media service Service and Control TPID
requirements tel URI, SIP URI or routable SIP URI
routing functionalities

Other service dependent features
Etc.
Service dependent input:
If external routeing:
tel URI, SIP URI or Routable Next Hop border gateway (naming or IP
SIP URI
addressing)
Destination Party Routing policy (i.e. load sharing, etc.)
IP addressing Performance, media Location OPID
and resources Resource allocation other protocol information TPID
available  requirements
etc. tel URI, SIP URI or routable SIP URI
Other service dependent characterizations
Etc

Next Hop Node or Gateway for transport
Transport Routeing
layer
Originating and destination IP address
IP internetworking routing policy

Figure 4: Common general purpose Routeing Model for NGN
ETSI

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12 ETSI TS 184 006 V2.1.1 (2008-09)
Considering figure 4, the common requirements for the routeing model are the following:
• Numbering and naming resolution functionality are applied for routable SIP URI determination, based on
specific mapping functionalities (database with relation with numbering/naming and destination CPs, etc.).
• The routeing process shall depend on the service characteristics and associated parameters that are meaningful
for determination of the route to the destination network. The process shall check and validate the service
requirements compatibility with user service profile and network resource availability.
• Originating and Terminating Party Public Identities shall be considered the essential information for routeing
process.
• Other service dependent parameters (for instance location parameters) can be considered if meaningful for
routeing process application.
Considering the different roles identified for routeing in figure 3, the routeing model for NGN will be appropriately
characterized to apply associated functionalities and input/output parameters.
Table 1: Requirements and actions for CP roles
CP roles Requirement and actions summing up
TPID is not resolved by CP's call control.
Originating
Service session setup request has to be forwarded to Transit or Triggering CP.
Triggering
tel URI or SIP URI is resolved in a "routable" SIP URI.
tel URI or SIP URI can not be resolved, since final destination is PSTN/ISDN or PLMN or an
Triggering for "All IP" network not compliant with ETSI NGN specifications.
interworking tel URI is forwarded to interworking function to apply specific resolution mechanisms and
procedures.
The domain part of the routable SIP URI corresponds to the domain of the terminating CP and
Terminating
end user shall be identified.
Call/session is to be delivered transparently to a terminating CP, basing on a tel URI or a
Routable SIP URI domain part different from the transit CP.
Transit
tel URI or SIP URI, after having identified routing towards terminating CP, is passed on
unmodified.

5.6 SIP and E.164 numbering
Also at interconnection [i.2] applies and table 2 shows the relationship between the Public ID that identifies a
Terminating and Originating user parties and the formats used in SIP header fields. The present document is focused on
E.164 numbering in tel URI or SIP URI coding formats.
Table 2: Public IDs and formats
Public ID (User parties) NGN coding formats

"User@Domain" format SIP URI
User/Service Identifiers
International or national E.164 tel URI
Numbers SIP URI

Thus the two formats that may be used are:
• tel URI for international or national numbers, e.g. tel: +431505641636.
• SIP URI, e.g. sip: +431505641636@;user=phone.
NOTE: "user=phone" is appended where the user part of the SIP URI is a string that is the same as a tel URI.
Additionally, the SIP "phone-context" parameter is used in case of national E.164 numbers and other digit
strings that are non-E.164 numbers.
ETSI

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