SIST-TS ETSI/TS 102 051 V1.1.1:2005

ENUM Administration in Europe

Development of a set of basic principles that should be adhered to maximise benefits from publicly available ENUM implementations within Europe.

Upravljanje sistema ENUM v Evropi

General Information

• Status: Published
• Publication Date: 31-Dec-2004
• ICS: 33.040.30 - Switching and signalling systems
• Technical Committee: SPN - Services and Protocols for Networks
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-2005
• Due Date: 01-Jan-2005
• Completion Date: 01-Jan-2005
• Ref Project: ETSI TS 102 051 V1.1.1 (2002-07) - ENUM Administration in Europe

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TS ETSI/TS 102 051 V1.1.1:2005
01-januar-2005
Upravljanje sistema ENUM v Evropi
ENUM Administration in Europe
Ta slovenski standard je istoveten z: TS 102 051 Version 1.1.1
ICS:
33.040.30 Komutacijski in signalizacijski Switching and signalling
sistem systems
SIST-TS ETSI/TS 102 051 V1.1.1:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS ETSI/TS 102 051 V1.1.1:2005

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SIST-TS ETSI/TS 102 051 V1.1.1:2005

ETSI TS 102 051 V1.1.1 (2002-07)
Technical Specification


ENUM Administration in Europe

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 2 ETSI TS 102 051 V1.1.1 (2002-07)



Reference
DTS/SPAN-110106
Keywords
ENUM
ETSI
650 Route des Lucioles
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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

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SIST-TS ETSI/TS 102 051 V1.1.1:2005
 3 ETSI TS 102 051 V1.1.1 (2002-07)
Contents
Intellectual Property Rights.5
Foreword.5
1 Scope.6
2 References.6
3 Definitions and abbreviations.6
3.1 Definitions.6
3.2 Abbreviations.8
4 Background.8
5 Description of ENUM.9
6 Opportunities threats and risks.12
6.1 Possible opportunities from ENUM .12
6.2 Possible threats from ENUM.13
6.3 Possible risks from specific implementations of ENUM.13
6.3.1 Integrity and security aspects.13
6.3.2 Abuse of market power.14
6.3.3 Universal resolvability and uniqueness of data in DNS.14
6.4 Other risks.15
7 Principles for ENUM implementation within Europe.15
7.1 Basic principles.15
7.2 Opt-in principle for the individual E.164 number holder .16
7.3 Principle for calling users and communications providers.16
8 Functional model.16
9 DNS responsibilities.17
9.1 Administrative responsibility for a domain .18
9.2 Registry for a domain .18
9.3 Registrar for a domain.18
10 General administrative and operating assumptions and requirements .18
10.1 ENUM Tier 1 manager assumptions .19
10.2 ENUM Tier 1 registry assumptions.19
10.3 ENUM Tier 2 Nameserver Provider assumptions .19
10.4 ENUM Registrar assumptions.20
10.5 Application Service Provider assumptions.21
10.6 Registrant assumptions.21
10.7 Validation assumptions.21
10.8 Removal assumption.21
10.9 Other assumptions.22
11 Operational and administrative processes .22
11.1 Processes for the provision of records in ENUM database at the Tier 0 level .22
11.2 Processes for the provision of records in the databases at the Tier 1 and Tier 2 levels.22
11.2.1 Registration of an E.164 number in the ENUM database.22
11.2.2 Processes for creation, modification and deletion of NAPTR Records in the Tier 2 database .23
11.2.3 Processes for removal of E.164 numbers from ENUM databases .24
11.3 Processes for changing Registrars .25
11.4 Other provisioning processes .26
12 Considerations in development and assessment of options for national implementations.26
12.1 Validation.26
12.2 Types of numbers .29
12.3 Openness to competition .29
12.4 Complexity and effort associated with provisioning .29
ETSI

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 4 ETSI TS 102 051 V1.1.1 (2002-07)
13 Recommendation for ENUM implementation within Europe.29
Annex A (informative): Examples for grouping of functionalities in national implementations.31
A.0 Introduction.31
A.1 Example 1.32
A.2 Example 2.34
A.3 Example 3.36
A.4 Example 4.38
Annex B (informative): ENUM entities - functions and responsibilities .40
Annex C (informative): DNS Concepts.41
C.1 DNS related definitions.41
C.2 DNS administration related definitions.42
Annex D (informative): Bibliography.44
History .45

ETSI

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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 Technical Specification (TS) has been produced by ETSI Technical Committee Services and Protocols for
Advanced Networks (SPAN).
ETSI

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1 Scope
The present document aims to assist European countries in the development of their national implementations of
ENUM. The present document builds upon the concept of ENUM as specified in IETF RFC 2916 [1] limited to E.164.
It introduces a set of basic principles that should be adhered to in order to maximize potential benefits from publicly
available ENUM implementations within Europe. A functional architecture for ENUM administration is put forward
and a number of options for provisioning flows are also proposed.
ENUM-like mechanisms can also be used for other identifiers or purposes such as private dialling plans, routeing, etc.
These functions are out of the scope of the present document.
The description of applications that can be offered by using ENUM capabilities and the role to be performed by
Application Service Providers are specified in TS 102 055 (see bibliography).
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• 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.
• For a non-specific reference, the latest version applies.
[1] IETF RFC 2916: "E.164 number and DNS".
[2] IETF RFC 1591: "Domain Name System Structure and Delegation".
[3] ITU-T Recommendation E.105 (08/92): "International telephone service".
[4] ITU-T Recommendation E.164 (05/97): "The international public telecommunication numbering
plan".
[5] ITU-T Recommendation E.191 (03/00): "B-ISDN addressing".
[6] IETF RFC 954: "NICNAME/WHOIS".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
accreditation: processes by which organizations are approved to act as the entities at the Tier 1 or Tier 2 levels
NOTE: The nature of accreditation, indeed whether it applies at all, is a national matter.
Application Service Provider (ASP): entity that provides specific application(s) which may be linked to an E.164
number using ENUM e.g. email or voice messaging to the end user
assignment entity: entity (e.g. Telephony service provider or National Number Plan Administrator or his agent)
responsible for the assignment of E.164 numbers to end users
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designated manager or responsible administrative organization: entity, in any level of the ENUM-based
architecture, which is responsible for a domain
NOTE: See clause 9.1 of the present document.
domain: set of host names within the DNS consisting of a single domain name and all the domain names below it
domain name: unique designator made up of symbols separated by dots
NOTE: The individual words or characters between the dots are called labels. The label furthest right represents
the top level domain. The second most right represents the second level of domain, or "second level
domain.
E.164: International Public Telecommunication Numbering Plan
NOTE: See ITU-T Recommendation E.164 [4].
E.164 Number: number taken from ITU-T Recommendation E.164
ENUM root: domain in which ENUM is hosted (according to IETF RFC 2916, this is e164.arpa)
ENUM domain name: domain name for an E.164 number
ENUM database: ENUM database is that part of the DNS below the ENUM root
ENUM end user: assignee of an E.164 number who has agreed to insert its E.164 number in the ENUM DNS-based
architecture
ENUM registrar: entity that provides direct services to domain name registrants by processing name registrations
ENUM registrant: entity initiating the ENUM registration process (end user or agent)
ENUM subscriber: assignee of an E.164 number who has agreed to insert its E.164 number in the ENUM DNS-based
architecture
ENUM Tier 0: level in the tiered architecture corresponding to the ENUM root, i.e. e164.arpa
NOTE: Records at this level contain pointers to Tier 1 for an E.164 Country Code or portion thereof.
ENUM Tier 1: level in the tiered architecture corresponding to the E.164 Country Code (CC), i.e. .e164.arpa
NOTE: Records at this level contain pointers to Tier 2 for an E.164 number.
ENUM Tier 2: level in the tiered architecture corresponding to the E.164 number, i.e., ..e164.arpa
NOTE: Records at this level contain NAPTR records for an E.164 number.
ENUM Tier 2 Nameserver Provider: entity responsible for the servers within DNS that hold the NAPTR resource
records
NOTE: In some other documents this entity is also referred to as the ENUM Tier 2 Registry or the ENUM Tier 2
provider.
National Number Plan Administrator (NNPA): entity responsible for the administration of a national numbering
Plan that is part of the international E.164 numbering plan
number portability: ability of an end user to change location within a geographic area, between service providers or
services, without changing their number
opt in: concept by which no action is taken unless with the explicit permission of the end user
telephony service provider: entity that provides the telephony service for which an E.164 number is assigned. In most
cases the telephony service provider may act as the assignment entity
Uniform Resource Identifier (URI): compact string of characters for identifying an abstract or physical resource that
is accessible via the Internet
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Uniform Resource Locator (URL): refers to the subset of URI that identify resources via a representation of their
primary access mechanism (e.g., their network "location"), rather than identifying the resource by name or by some
other attribute(s) of that resource e.g. http://www.etsi.org or sip:[e-mail]
validation entity: entity (e.g. Telephony service provider or National Number Plan Administrator or his agent) that
validates the assignment of E.164 numbers to end users
WHOIS: database function that provides a look up capability of those on the Internet
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ASP Application Service Provider
DNS Domain Name System
DNSSEC DNS SECurity extension
ENF European Numbering Forum
IAB Internet Architecture Board
IETF Internet Engineering Task Force
IP Internet Protocol
ISDN Integrated Services Digital Network
ISOC Internet Society
ITU-T International Telecommunication Union - Telecommunication Standardization Sector
LS Location Server
NAPTR Naming Authority PoinTeR
NNPA National Number Plan Administrator
NRA National Regulatory Authority
ONP Open Network Provision
PSPDN Packet Switched Public Data Network
PSTN Public Switched Telephone Network
RFC Request For Comment (IETF related standard)
RRs (DNS) Resource Records
SCN Switched Circuit Network
SIP Session Initiation Protocol
TLD Top Level Domain
TSP Telephony Service Provider
URI Uniform Resource Identifier
URL Uniform Resource Locator
4 Background
ENUM is a mechanism (see note 1) that maps E.164 numbers to Internet domain names. Every E.164 number can
potentially be used in ENUM. All portions of international or national numbering plans can be considered for inclusion,
meaning that every E.164 number can potentially be used in ENUM. Much attention now surrounds ENUM as it
facilitates interworking between telephony networks and applications that are reliant on the Internet. ENUM transforms,
in real time, end users' E.164 numbers to other communications identities (see note 2) used for setting up connections.
For example, this could be used for communications from the circuit switched telephone network (PSTN) to IP-based
services and vice-versa. It can also assist end users who wish to be able to be reachable via several means of
communication. ENUM capabilities are described in more detail in clause 5 of the present document.
NOTE 1: While ENUM strictly refers to the mechanism, in practical terms it is also used to refer to the wider
implementation of ENUM, i.e. the populated database.
NOTE 2: Communications identity is a generic term including a name, a number or an address. For explanation of
these three terms refer to ITU-T Recommendation E.191 [5]. This new English term is introduced in the
present document in the absence of a suitable well-known generic English term covering both a name, a
number and an address for use in electronic communications networks (e.g. PSTN, ISDN, PLMN,
Internet and PSPDN).
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Following completion of work on IETF RFC 2916 [1] by the IETF which introduced the ENUM mechanism, the focus
of attention turned towards the ITU-T who began working with the ISOC/IAB to determine the Administrative
requirements (see note 3).
NOTE 3: ITU-T Study Group 2 is developing a Recommendation, E.A-ENUM "Principles and procedures for the
administration of E.164 geographic country codes for registration into the domain name system", and a
Supplement entitled "Operational and administrative issues associated with national implementations of
enum functions" which will offer guidance to national Administrations/NRA. Approval of the
Recommendation is targeted for 12/2002.
Work is now under way in some European countries in order to understand the implications of ENUM and how it could
be implemented. However this is occurring in a rather fragmented manner. Concerns over ENUM have also been
expressed by a number of other parties, including the European Commission (see note 4) in the production of a paper
that has been submitted to the ONP Committee. An experts group on Numbering, Naming and Addressing, created by
the ONP committee, will also be considering whether any specific action relating to ENUM is required.
NOTE 4: The ONP expert group meet in December 2001 and in January 2002. Their results were provided to the
ONP Committee. Then the ONP Committee made a contribution to the ITU-T SG2-meeting in May 2002
that was supported by the 15 MS in EU.
The numbering and addressing environment within Europe exhibits marked differences from that within the US and
other parts of the world, so it is considered important that Europe looks closely at the administration issues that occur
with ENUM. Efforts at drawing together a co-ordinated approach should not only result in a firm foundation for ENUM
activities within the European environment, but should also assist in enhancing the competitive communications
environment.
The present document is presented to assist with that task. It has been developed taking due account of the views and
comments of other key European bodies, including the European Numbering Forum (ENF).
NOTE 5: In the present document, for consistency, the domain e164.arpa will be mentioned as the ENUM root
domain of the ENUM DNS-based architecture. In the case that a different domain results from
discussions between ISOC and the ITU the basic principles articulated in this paper will apply.
The single domain that is referred to throughout the present document as for the ENUM Tier 0 domain, is the e164.arpa
domain. This domain is used only for convenience and given that domain is specified in IETF RFC 2916 [1], the IETF
protocol in which ENUM is described. This should not assume that this domain will be the final choice which the ITU
and relevant Internet governance bodies will agree on for the implementation of ENUM. The principles set in the
present document are independent of the final choice of the ENUM Tier 0 domain and should not preclude a single
authoritative solution at some future point in time, should this become agreed policy.
5 Description of ENUM
ITU-T Recommendation E.164 [4] describes the format and types of use of public telephone numbers (E.164 numbers).
ENUM is a term that has been adopted to describe a Domain Name System (DNS) based mechanism which maps E.164
numbers into URIs.
Via ENUM, an E.164 number can be used as a single front-end to a variety of communication identities by which an
end user can be contacted, including those used for phone, fax and email. This enables users who are the recipient of
communications to indicate the means by which they wish to be contacted through a single number. The details of these
communications identities can also be easily amended, added to, or updated without changing the number used for
access.
The communications identities that can be accessed via a look-up of ENUM data may be associated with a wide range
of applications, some of which are shown within figure 1.
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Typical Applications
Out
URI
ENUM
Instant
Messaging
DNS
InternetInternet
Voice
DomDomaainin
NaNammeess
Internet
Unified
Messaging
Fax
ININ
E.16E.1644
Switched
Personal
Circuit
Web Pages
(T(Teelleephonephone))
Networks
(SCN)
NumbersNumbers

Figure 1: Typical applications enabled through ENUM
Using ENUM capabilities, providers of IP telephony services could legitimately originate IP telephony calls from an
E.164 number or terminate IP telephony calls to an E.164 number that was assigned by the access network operator
rather than by the IP telephony service provider.
[phone] DNS returns record
as url
DNS
1 [phone]
tel:[phone]
2 Client formats url
Location
server
4 SIP Client initiates
INVITE to server
LS returns
using tel url 6
IP address
IP
of Gateway
Network
5 SIP server looks
up gateway
address from LS
[phone]
7 Call routed
to Gateway
IP address
PSTN
Gateway
8 Gateway
completes
call to PSTN

Figure 2: Typical call flows IP-PSTN
Figure 2 shows a typical call flow with a call originating on a SIP based network, in this example in Switzerland
(+41 number), contacting a user on a SIP (IP based) network in France (+33 number).
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4 DNS look up returns
DNS
[phone] NAPTR record with
[e-mail]
7 SIP server 6 DNS returns
routes call to SIP server IP
user address
IP
Network
[phone]
5
Gateway looks up
host for
[phone]
1
[e-mail]
PSTN
Gateway
2 [phone]
3 ( ENUM functionality)
formats url
7.8.8.5.0.3.7.2.2.1.4.e164.arpa

Figure 3: Typical call flows PSTN-IP
Figure 3 shows a typical call flow where a call originating on a on a circuit switched network in this case in France (+33
number), contacts a user on a SIP (IP based) network in Switzerland (+41 number).
It should be noted that ENUM can facilitate a wide range of different applications by providing access using an E.164
number, however ENUM itself does not provide these applications, merely a method that can facilitate access.
ENUM utilizes a mechanism developed by the Internet Engineering Task Force (IETF), specified in
IETF RFC 2916 [1]. As stated previously ENUM resolution utilizes the DNS for resolution. The part of the DNS tree
applicable to ENUM is shown in figure 4.
Other roots
The root node
"" ""
arpa .com .xxx
.net .yyy
.
... ...
second- second- second- second- second-
e164.arpa in-addr
level node level node level node level node level node
3.3.e164.arpa
4.4.e164.arpa
third-level third-level
node node
6.4.e164.arpa
0.0.0.0.6.9.4.3.1.1.4.4.e164.arpa 0.0.2.4.4.9.2.9.4.3.3.e164.arpa
4.3.2.1.6.7.9.8.6.4.e164.arpa

Figure 4: shows how ENUM fits into the DNS structure
The DNS forms a distributed database which holds information about Internet hosts. Each domain path spreads down
from one 'root' domain at the highest level through its sub domains. In written form each sub domain is indicated by the
insertion of a dot (.) within the written string. “Other roots” can be found in clause 6.3.3.
ETSI

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Second-level domains in other top level domains (e.g. enumworld.org a
...