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Internet Protocol (IP) has now
evolved beyond data-only networks to encompass an integrated,
converged world of voice and data communication. What was a secondary
transport medium is now becoming the primary medium for all forms of
communication, especially Voice over Internet Protocol (VoIP). At the
enterprise level, businesses are now using mature IP technology for
both telephony and other data applications.
What is a telephone number?
Long ago, a telephone number
was an address. Today, numbers are logical entities that can be
mapped to all sorts of devices and services. ITU-T E.164 defines the
international space for telephone numbers (country codes). National
governments [are] responsible for the assignment of their numbering
space
The ITU & E.164 Numbering
The International
Telecommunications Union (ITU) is an international treaty organization
under the United Nations that develops Standards and Recommendations
for telecommunications networks.
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Recommendation E.164 describes the international public
telecommunication numbering plan, e.g. country code assignment
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Recommendation E.190 describes the general principles to be
utilized in the assignment of ITU-T E-Series international numbering
resources.
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Recommendation E.164.1 describes the procedures and criteria for
the reservation, assignment, and reclamation of E.164 country codes
and associated Identification Code (IC) assignments. The criteria
and procedures are provided as a basis for the effective and
efficient utilization of the available E.164 numbering resources.
ITU plays an administrative role
in validating a country’s E.164.arpa ENUM delegation to ensure that
only the government or a country’s designated Number Administration
can authorize its country code be placed in the ENUM TLD “tree” by
RIPE NCC.
Why use a Telephone Number?
E.164 numbers on the telephone
network are unique, accurate, current, and global. Also, E.164 Plan is
“Authoritative” and trusted to produce consistency across the PSTN.
There is widespread use of E.164 numbers as identifiers far beyond the
scope of the public network. (Example: Tech Support for my laptop,
uses my office phone number to retrieve information from their
tracking system: status, history)
Why use Domain Names?
The Domain Name System (DNS)
transforms domain names (www.google.com)
into IP addresses (966.102.7.147). It is hierarchically structured
resolution and scales by hierarchical distribution and caching.
One of the most widespread ways
to identify “things” on the Internet is use of domain names that:
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Combines host name and network
name
(Hierarchical; written as labels separated by “.”)
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Assumes all networks are
interconnected
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Is unique, accurate, current,
and global
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Is flexible and extensible.
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Requires administration
What is ENUM?
Electronic Numbering is a
standard developed by the Internet Engineering Task Force (IETF). It
is a protocol (RFC 3761) that converts standard E.164 international
telephone numbers into Internet addresses using the Domain Name System
(DNS) so that resources associated with a telephone number can be
resolved in the IP domain.
ENUM DNS Architecture
Tier 0 is the Top Level, Domain, e164.arpa. The
“Global” ENUM Tier operated by RIPE.
Each Country Code will have its own Tier 1
registry, the “National” ENUM Tier.
Specific information linked to
each telephone number will be stored by service providers at the Tier
2 level, the “Competitive” ENUM Tier.
Telephone Numbers over IP = ENUM
Typically a Uniform Resource
Indicator (URI) is used in protocols such as SIP to depict a telephone
number (similar to HTTP URLs or email addresses)
ENUM reuses the Domain Name
Service (DNS) system for translating telephone numbers into URIs. It’s
a query-based routing system.
ENUM - One Number to Any Device
ENUM enables convergence because:
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ENUM bridges the technology gap
between the public Internet and the Public Switched Telephone
Network (PSTN)
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ENUM provides the
interconnecting IP/PSTN and IP/IP traffic a fast and efficient
method of finding out which type of network a called party is on and
what address it is using
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ENUM becomes increasingly
essential as applications like VoIP become more widely adopted
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ENUM provides “intelligent
network” capabilities that allow both Internet users and telephone
network users to benefit from Internet-based applications
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ENUM supports new IP enabled
services (VoIP, Instant Messaging, Video etc.) use of Telephone
Numbers
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ENUM enables customer
communications on a global scale while increasing the degree of
control they have over how and when, and to whom they communicate
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ENUM contains validation and
verification components that maintain privacy and security of end
user and carrier data
Karen Mulberry
Sr. Director, Distinguished Member of Technical Staff
Advanced Services - Technology Initiatives
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