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{{short description|ITU-T Recommendation}}
{{short description|ITU-T Recommendation for telephone numbering}}
{{For|the food additive E164|Saffron}}

{{Infobox technology standard
{{Infobox technology standard
| image = Phone number setup.png
| title = Recommendation ITU-T E.164
⚫
| long_name = The international public telecommunication numbering plan
| title = ITU-T Recommendation E.164
⚫
| long_name =the international public telecommunication numbering plan
| caption =
| status = In force
| status = In force
| year_started = 1984
| year_started = 1984
| version = (06/20)
| version_date = June 2020
| version_date = June 2020
| preview =
| preview_date =
| organization = [[ITU-T]]
| organization = [[ITU-T]]
| committee = Study Group 2
| committee = Study Group 2
| base_standards =
| related_standards = [[E.123]], [[E.163]]
| related_standards = [[E.123]], [[E.163]]
| abbreviation =
| domain = [[telephony]]
| domain = [[telephony]]
| license = Freely available
| website = https://www.itu.int/rec/T-REC-E.164/
| website = https://www.itu.int/rec/T-REC-E.164/
}}
}}
[[File:Phone_number_setup.png|thumb|right]]

'''E.164''' is an [[international standard]] ([[ITU-T]] Recommendation), titled ''The international public telecommunication numbering plan'', that defines a [[Telephone numbering plan|numbering plan]] for the worldwide [[public switched telephone network]] (PSTN) and some other data [[telecommunications network|networks]].
'''E.164''' is an [[international standard]] ([[ITU-T]] Recommendation), titled ''The international public telecommunication numbering plan'', that defines a [[Telephone numbering plan|numbering plan]] for the worldwide [[public switched telephone network]] (PSTN) and some other data [[telecommunications network|networks]].


E.164 defines a general format for international [[telephone number]]s. Plan-conforming numbers are limited to a maximum of 15 digits, excluding the [[international call prefix]].<ref name=":0">{{Cite web|url=https://www.itu.int/rec/T-REC-E.164/|title=E.164 : The international public telecommunication numbering plan|website=www.itu.int|page=11|url-status=live|archive-url=https://web.archive.org/web/20191106122855/https://www.itu.int/rec/T-REC-E.164/|archive-date=2019-11-06|access-date=2019-11-12}}</ref>
E.164 defines a general format for international [[telephone number]]s. Plan-conforming telephone numbers are limited to only digits and to a maximum of fifteen digits.<ref name=":0">{{Cite web|url=https://www.itu.int/rec/T-REC-E.164/|title=E.164 : The international public telecommunication numbering plan|website=www.itu.int|page=11|url-status=live|archive-url=https://web.archive.org/web/20191106122855/https://www.itu.int/rec/T-REC-E.164/|archive-date=2019-11-06|access-date=2019-11-12}}</ref> The specification divides the digit string into a country code of one to three digits, and the subscriber telephone number of a maximum of twelve digits.


Alternative formats (with area codes and country specific numbers) are available. Any country-specific [[International direct dialing#International call prefix|international call prefix]]es are not contained in the specification.
As defined by the ITU-T, the E.164 general format must contain only digits split as follows:
* Country code (1 to 3 digits)
* Subscriber number (max 12 digits)

Alternative formats (with area codes and country specific numbers) are available.


The title of the original version and first revision of the E.164 standard was ''Numbering Plan for the ISDN Era''
The title of the original version and first revision of the E.164 standard was ''Numbering Plan for the ISDN Era''

==Recommendations==
⚫
===E.163===
⚫
E.163 was the former [[ITU-T]] recommendation for describing [[telephone]] numbers for the [[public switched telephone network]] (PSTN). In the United States, this was formerly referred to as a ''directory number''. E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.163|title=E.163 : Numbering plan for the international telephone service|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20190729130203/https://www.itu.int/rec/T-REC-E.163|archive-date=2019-07-29|access-date=2019-11-12}}</ref>

⚫
===E.164.1===
⚫
This recommendation describes the procedures and criteria for the reservation, assignment, and reclamation of E.164 country codes and associated ''identification code'' (IC) assignments.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.1|title=E.164.1 : Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs)|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20191112172208/https://www.itu.int/rec/T-REC-E.164.1|archive-date=2019-11-12|access-date=2019-11-12}}</ref> The criteria and procedures are provided as a basis for the effective and efficient utilization of the available E.164 numbering resources.

⚫
===E.164.2===
⚫
This recommendation contains the criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code [[+991]] for the purpose of conducting an international non-commercial trial.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.2|title=E.164.2 : E.164 numbering resources for trials|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20191112172324/https://www.itu.int/rec/T-REC-E.164.2|archive-date=2019-11-12|access-date=2019-11-12}}</ref>

===E.164.3===
⚫
This recommendation describes the principles, criteria, and procedures for the assignment and reclamation of resources within a shared E.164 country code for groups of countries.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.3|title=E.164.3 : Principles, criteria and procedures for the assignment and reclamation of E.164 country codes and associated identification codes for groups of countries|website=www.itu.int|url-status=dead|archive-url=https://web.archive.org/web/20191112172813/https://www.itu.int/rec/T-REC-E.164.3|archive-date=2019-11-12|access-date=2019-11-12}}</ref> These shared country codes will coexist with all other E.164-based country codes assigned by the ITU. The resource of the shared country code consists of a ''country code'' and a ''group identification code'' (CC + GIC) and provides the capability for a group of countries to provide telecommunication services within the group. The Secretariat of the ITU Standardization Sector ([[ITU-T]]), the Telecommunication Standardization Bureau (TSB) is responsible for the assignment of the CC + GIC.


==Numbering formats==
==Numbering formats==
The E.164 recommendation provides the telephone number structure and functionality for three categories of telephone numbers used in international public [[telecommunication]]:
The E.164 recommendation provides the telephone number structure and functionality for five categories of telephone numbers used in international public [[telecommunications]].


For each of the categories, it details the components of the numbering structure and the digit analysis required for successful [[routing]] of calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialing procedures, and addressing for Geographic-based [[ISDN]] calls. Specific E.164-based applications which differ in usage are defined in separate recommendations.
For each of the categories, it details the components of the numbering structure and the digit analysis required for successful [[routing]] of calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialing procedures, and addressing for Geographic-based [[ISDN]] calls. Specific E.164-based applications which differ in usage are defined in separate recommendations.
Line 42: Line 47:
{| class="wikitable"
{| class="wikitable"
|-
|-
! Country Code
! National Destination Code
! National Destination Code
! Subscriber Number
! National (significant)
|- style="text-align:center;"
|- style="text-align:center;"
||''cc'' = 1 to 4 digits
|| 1 to 3 digits
| maximum = 15 − ''cc'' = 11 to 14 digits
| colspan=2 | maximum 15 digits − number of digits in the country code
|-
|-
| colspan="3" style="text-align:center;"| International public telecommunication number for geographic areas (maximum 15 digits)
| colspan="3" style="text-align:center;"| maximum 15 digits
|}
|}


Line 57: Line 63:
! Global Subscriber Number
! Global Subscriber Number
|- style="text-align:center;"
|- style="text-align:center;"
||''cc'' = 3 digits
|| 3 digits
| maximum 12 digits
| maximum 12 digits
|-
|-
| colspan="2" style="text-align:center;"| International public telecommunication number for global services (maximum 15 digits)
| colspan="2" style="text-align:center;"| maximum 15 digits
|}
|}


Line 72: Line 78:
! Subscriber Number
! Subscriber Number
|- style="text-align:center;"
|- style="text-align:center;"
||''cc'' = 1 to 3 digits
|| 3 digits
||''x'' = 1 to 4 digits
|| 1 to 4 digits
|| maximum = 15 − (''cc'' + ''x'') = 8 to 13 digits
|| maximum 12 digits − number of digits in the identification code
|-
|-
| colspan="3" style="text-align:center;"| International public telecommunication number for networks (maximum 15 digits)
| colspan="3" style="text-align:center;"| maximum 15 digits
|}
|}


===Groups of countries===
===Groups of countries===
{| class="wikitable
{| class="wikitable
! Country Code
! Group Identification Code
! Group Identification Code
! Subscriber Number
|- style="text-align:center;"
|- style="text-align:center;"
||''cc'' = 1 to 3 digits
|| 3 digits
||''gic'' = 1 digit
|| 1 digit
|| maximum = 15 − (''cc'' + ''gic'') = 11 digits
|| maximum 11 digits
|-
|-
| colspan="3" style="text-align:center;"| International public telecommunication number for groups of countries (maximum 15 digits)
| colspan="3" style="text-align:center;"| maximum 15 digits
|}
|}


==Recommendations==
===Trials===
{| class="wikitable"
⚫
=== E.163 ===
|-
⚫
'''E.163''' was the former [[ITU-T]] recommendation for describing [[telephone]] numbers for the [[public switched telephone network]] (PSTN). In the [[United States]], this was formerly referred to as a ''directory number''. E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.163|title=E.163 : Numbering plan for the international telephone service|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20190729130203/https://www.itu.int/rec/T-REC-E.163|archive-date=2019-07-29|access-date=2019-11-12}}</ref>
! Fixed code
! Trial Identification Code
! Subscriber Number
|- style="text-align:center;"
|| 991
|| 1 digit
|| maximum 11 digits
|-
| colspan="3" style="text-align:center;"| maximum 15 digits
|}


===E.164.1===
==Uses of E.164 numbers==
E.164 numbers were originally defined for use in the worldwide [[public switched telephone network]] (PSTN). The early PSTN collected routing digits from users (e.g. on a dial pad), signaled those digits to each telephony switch, and used the numbers to determine how to ultimately reach the called party.
⚫
This recommendation describes the procedures and criteria for the reservation, assignment, and reclamation of E.164 country codes and associated ''identification code'' (IC) assignments.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.1|title=E.164.1 : Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs)|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20191112172208/https://www.itu.int/rec/T-REC-E.164.1|archive-date=2019-11-12|access-date=2019-11-12}}</ref> The criteria and procedures are provided as a basis for the effective and efficient utilization of the available E.164 numbering resources.

⚫
===E.164.2===
⚫
This recommendation contains the criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code [[+991]] for the purpose of conducting an international non-commercial trial.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.2|title=E.164.2 : E.164 numbering resources for trials|website=www.itu.int|url-status=live|archive-url=https://web.archive.org/web/20191112172324/https://www.itu.int/rec/T-REC-E.164.2|archive-date=2019-11-12|access-date=2019-11-12}}</ref>

⚫
===E.164.3===
⚫
This recommendation describes the principles, criteria, and procedures for the assignment and reclamation of resources within a shared E.164 country code for groups of countries.<ref>{{Cite web|url=https://www.itu.int/rec/T-REC-E.164.3|title=E.164.3 : Principles, criteria and procedures for the assignment and reclamation of E.164 country codes and associated identification codes for groups of countries|website=www.itu.int|url-status=dead|archive-url=https://web.archive.org/web/20191112172813/https://www.itu.int/rec/T-REC-E.164.3|archive-date=2019-11-12|access-date=2019-11-12}}</ref> These shared country codes will coexist with all other E.164-based country codes assigned by the ITU. The resource of the shared country code consists of a ''country code'' and a ''group identification code'' (CC + GIC) and provides the capability for a group of countries to provide telecommunication services within the group. The Secretariat of the ITU Standardization Sector ([[ITU-T]]), the Telecommunication Standardization Bureau (TSB) is responsible for the assignment of the CC + GIC.

⚫
==Uses of E.164 Numbers==
E.164 numbers were originally defined for use in the worldwide [[public switched telephone network]] (PSTN). The early PSTN collected routing digits from users (e.g. on a dial pad), signaled those digits to each telephony switch, and used the numbers to determine how to ultimately reach the called party. ITU-T [[E.123]] entitled ''Notation for national and international telephone numbers, e-mail addresses and Web addresses'' provides guidance when printing E.164 telephone numbers. This format includes prefixing numbers with a plus sign ([[Plus and minus signs#Plus sign|+]]) and including visual separators like hyphen ([[Plus and minus signs#Minus sign|-]]). As the PSTN evolved a number of standards have been adopted that incorporate the ITU-T E.164 standard.


ITU-T [[E.123]] entitled ''Notation for national and international telephone numbers, e-mail addresses and web addresses'' provides guidance when printing E.164 telephone numbers. This format includes the recommendation of prefixing international telephone numbers with a plus sign ([[Plus and minus signs#Plus sign|+]]) and using only spaces for digit grouping.
===SIP Usage of E.164 Numbers===
With the evolution of the [[Public switched telephone network]] from [[Time-division multiplexing|TDM]] [[Circuit switching|Circuit Switching]] to IP Data Networks using [[Voice over IP]], the IETF SIP protocol defined in the Internet Engineering Task Force RFC 3261<ref>{{cite IETF|title=SIP: Session Initiation Protocol|rfc=3261|date=June 2002|publisher=[[Internet Engineering Task Force|IETF]]|access-date=January 11, 2021}}</ref> was introduced to setup sessions between users for voice, video, and multi-media.


The presentation of a number at the called (B-party) device is usually prefixed with the plus sign ([[Plus and minus signs#Plus sign|+]]), indicating that the number includes the [[country calling code]]. Prefixing of the number with "+" is called the ''globalized'' format of an E.164 number and is defined in the Internet Engineering Task Force RFC 2806.<ref>{{cite IETF|title=URLs for Telephone Calls|rfc=2806|section=2.2|date=April 2000|publisher=[[Internet Engineering Task Force|IETF]]|access-date=January 11, 2021}}</ref>
The presentation of a telephone number with the plus sign ([[Plus and minus signs#Plus sign|+]]) indicates that the number should be dialed with an [[List of international call prefixes|international calling prefix]], in place of the plus sign. The number is presented starting the [[country calling code]]. This is called the ''globalized'' format of an E.164 number, and is defined in the Internet Engineering Task Force {{IETF RFC|2806}}.<ref>{{cite IETF|title=URLs for Telephone Calls|rfc=2806|section=2.2|date=April 2000|publisher=[[Internet Engineering Task Force|IETF]]|access-date=January 11, 2021}}</ref> The international calling prefix is a [[trunk code]] to reach an international circuit in the country of call origination.<ref>{{Cite book|url=https://books.google.com/books?id=iQBmBIBfWXEC&pg=PT172|title=Implementing Cisco Unified Communications Manager, Part 2 (CIPT2) Foundation Learning Guide: (CCNP Voice CIPT2 642-457)|last=Olsen|first=Chris|date=2011-08-01|publisher=Cisco Press|isbn=9780132312141|pages=172|language=en}}</ref>


⚫
===DNS Mapping of E.164 numbers===
This is done by the B-party subscriber's network by usually looking at the NOA (Nature Of Address) field of the signaling messages or through other pattern based number analysis using rules derived from E.164. When dialing, the number must typically be prefixed with the appropriate international call prefix (in place of the plus sign), which is a [[trunk code]] to reach an international circuit from within the country of call origination.<ref>{{Cite book|url=https://books.google.com/books?id=iQBmBIBfWXEC&pg=PT172|title=Implementing Cisco Unified Communications Manager, Part 2 (CIPT2) Foundation Learning Guide: (CCNP Voice CIPT2 642-457)|last=Olsen|first=Chris|date=2011-08-01|publisher=Cisco Press|isbn=9780132312141|pages=172|language=en}}</ref>

===DNS Mapping of E.164 Numbers===
{{main|Telephone number mapping}}
{{main|Telephone number mapping}}
Some national telephone administrations and telephone companies have implemented an [[Internet]]-based database for their numbering spaces. E.164 numbers may be used in the [[Domain Name System]] (DNS) of the [[Internet]] in which the second-level domain e164.arpa has been reserved for [[telephone number mapping]] (ENUM). In the system, any phone number may be mapped into a [[domain name]] using a reverse sequence of subdomains for each digit. For example, the telephone number {{gaps|+1|999|555|0123}} translates to the domain name {{mono|3.2.1.0.5.5.5.9.9.9.1.e164.arpa}}.
Some national telephone administrations and telephone companies have implemented an [[Internet]]-based database for their numbering spaces. E.164 numbers may be registered in the [[Domain Name System]] (DNS) of the [[Internet]] in which the second-level domain e164.arpa has been reserved for [[telephone number mapping]] (ENUM). In the system, any telephone number may be mapped into a [[domain name]] using a reverse sequence of subdomains for each digit. For example, the telephone number {{gaps|+1|999|555|0123}} translates to the domain name {{mono|3.2.1.0.5.5.5.9.9.9.1.e164.arpa}}. When a number is mapped, a DNS query may be used to locate the service facilities on the Internet that accept and process telephone calls to the owner of record of the number, using, for example, the [[Session Initiation Protocol]] (SIP), a call-signaling [[VoIP]] protocol whose [[SIP address]]es are similar in format (user@domain...) to e-mail addresses. This allows a direct, end-to-end Internet connection without passing through the public switched telephone network.

When a number is mapped, a DNS query may be used to locate the service facilities on the Internet that accept and process telephone calls to the owner of record of the number, using, for example, the [[Session Initiation Protocol]] (SIP), a call-signaling [[VoIP]] protocol whose [[SIP address]]es are similar in format (user@domain...) to e-mail addresses.

This allows a direct, end-to-end Internet connection without passing to the public switched telephone network (and back) and without incurring PSTN tolls.

As this is effectively a free call, there is little incentive for carriers to promote e164 DNS service. The e164.arpa domain is in production status {{asof|2013|lc=on}} only in a few European nations ([[Austria]], [[Czech Republic]], [[Finland]], [[Germany]], [[Ireland]], [[Lithuania]], [[Poland]], [[Romania]], [[Netherlands]], [[United Kingdom]]).<ref>{{cite web|url=http://enumdata.org|title=RIPE ENUM Working Group: Progress Matrix|publisher=Enumdata.org|access-date=26 October 2013}}</ref> [[Australia]] conducted a trial in 2007 but then abandoned further support of {{mono|.1.6.e164.arpa}}. Many nations have no {{mono|.e164.arpa}} implementation active.<ref>{{cite book|url=https://books.google.com/books?id=glJUa3f3rd4C&pg=PA312|title=Asterisk: The Definitive Guide|author=Russell Bryant|author2=Leif Madsen|author3=Jim Van Meggelen|date=2013-05-10|isbn=9781449332464|pages=312|access-date=2019-11-12}}</ref>


==See also==
==See also==
Line 127: Line 127:
*[[E.123]]
*[[E.123]]
*[[List of country calling codes]]
*[[List of country calling codes]]

==External Sources==
* [https://www.itu.int/rec/T-REC-E.164/en ITU National Number Plans Reference]


==References==
==References==

Latest revision as of 11:19, 22 November 2024

For the food additive E164, see Saffron.
Recommendation ITU-T E.164
The international public telecommunication numbering plan
StatusIn force
Year started1984
Latest versionJune 2020
OrganizationITU-T
CommitteeStudy Group 2
Related standardsE.123, E.163
Domaintelephony
Websitehttps://www.itu.int/rec/T-REC-E.164/

E.164 is an international standard (ITU-T Recommendation), titled The international public telecommunication numbering plan, that defines a numbering plan for the worldwide public switched telephone network (PSTN) and some other data networks.

E.164 defines a general format for international telephone numbers. Plan-conforming telephone numbers are limited to only digits and to a maximum of fifteen digits.[1] The specification divides the digit string into a country code of one to three digits, and the subscriber telephone number of a maximum of twelve digits.

Alternative formats (with area codes and country specific numbers) are available. Any country-specific international call prefixes are not contained in the specification.

The title of the original version and first revision of the E.164 standard was Numbering Plan for the ISDN Era

Recommendations

E.163

E.163 was the former ITU-T recommendation for describing telephone numbers for the public switched telephone network (PSTN). In the United States, this was formerly referred to as a directory number. E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.[2]

E.164.1

This recommendation describes the procedures and criteria for the reservation, assignment, and reclamation of E.164 country codes and associated identification code (IC) assignments.[3] The criteria and procedures are provided as a basis for the effective and efficient utilization of the available E.164 numbering resources.

E.164.2

This recommendation contains the criteria and procedures for an applicant to be temporarily assigned a three-digit identification code within the shared E.164 country code +991 for the purpose of conducting an international non-commercial trial.[4]

E.164.3

This recommendation describes the principles, criteria, and procedures for the assignment and reclamation of resources within a shared E.164 country code for groups of countries.[5] These shared country codes will coexist with all other E.164-based country codes assigned by the ITU. The resource of the shared country code consists of a country code and a group identification code (CC + GIC) and provides the capability for a group of countries to provide telecommunication services within the group. The Secretariat of the ITU Standardization Sector (ITU-T), the Telecommunication Standardization Bureau (TSB) is responsible for the assignment of the CC + GIC.

Numbering formats

The E.164 recommendation provides the telephone number structure and functionality for five categories of telephone numbers used in international public telecommunications.

For each of the categories, it details the components of the numbering structure and the digit analysis required for successful routing of calls. Annex A provides additional information on the structure and function of E.164 numbers. Annex B provides information on network identification, service parameters, calling/connected line identity, dialing procedures, and addressing for Geographic-based ISDN calls. Specific E.164-based applications which differ in usage are defined in separate recommendations.

The number categories are all based on a fifteen-digit numbering space. Before 1997, only twelve digits were allowed. The definition does not include any international call prefixes, necessary for a call to reach international circuits from inside the country of call origination.

Geographic areas

Country Code National Destination Code Subscriber Number
1 to 3 digits maximum 15 digits − number of digits in the country code
maximum 15 digits

Global services

Country Code Global Subscriber Number
3 digits maximum 12 digits
maximum 15 digits

[1] Figure 2

Networks

Country Code Identification Code Subscriber Number
3 digits 1 to 4 digits maximum 12 digits − number of digits in the identification code
maximum 15 digits

Groups of countries

Country Code Group Identification Code Subscriber Number
3 digits 1 digit maximum 11 digits
maximum 15 digits

Trials

Fixed code Trial Identification Code Subscriber Number
991 1 digit maximum 11 digits
maximum 15 digits

Uses of E.164 numbers

E.164 numbers were originally defined for use in the worldwide public switched telephone network (PSTN). The early PSTN collected routing digits from users (e.g. on a dial pad), signaled those digits to each telephony switch, and used the numbers to determine how to ultimately reach the called party.

ITU-T E.123 entitled Notation for national and international telephone numbers, e-mail addresses and web addresses provides guidance when printing E.164 telephone numbers. This format includes the recommendation of prefixing international telephone numbers with a plus sign (+) and using only spaces for digit grouping.

The presentation of a telephone number with the plus sign (+) indicates that the number should be dialed with an international calling prefix, in place of the plus sign. The number is presented starting the country calling code. This is called the globalized format of an E.164 number, and is defined in the Internet Engineering Task Force RFC 2806.[6] The international calling prefix is a trunk code to reach an international circuit in the country of call origination.[7]

DNS Mapping of E.164 numbers

Main article: Telephone number mapping

Some national telephone administrations and telephone companies have implemented an Internet-based database for their numbering spaces. E.164 numbers may be registered in the Domain Name System (DNS) of the Internet in which the second-level domain e164.arpa has been reserved for telephone number mapping (ENUM). In the system, any telephone number may be mapped into a domain name using a reverse sequence of subdomains for each digit. For example, the telephone number +19995550123 translates to the domain name 3.2.1.0.5.5.5.9.9.9.1.e164.arpa. When a number is mapped, a DNS query may be used to locate the service facilities on the Internet that accept and process telephone calls to the owner of record of the number, using, for example, the Session Initiation Protocol (SIP), a call-signaling VoIP protocol whose SIP addresses are similar in format (user@domain...) to e-mail addresses. This allows a direct, end-to-end Internet connection without passing through the public switched telephone network.

See also

External Sources

References

  1. ^ a b "E.164 : The international public telecommunication numbering plan". www.itu.int. p. 11. Archived from the original on 2019-11-06. Retrieved 2019-11-12.
  2. ^ "E.163 : Numbering plan for the international telephone service". www.itu.int. Archived from the original on 2019-07-29. Retrieved 2019-11-12.
  3. ^ "E.164.1 : Criteria and procedures for the reservation, assignment and reclamation of E.164 country codes and associated identification codes (ICs)". www.itu.int. Archived from the original on 2019-11-12. Retrieved 2019-11-12.
  4. ^ "E.164.2 : E.164 numbering resources for trials". www.itu.int. Archived from the original on 2019-11-12. Retrieved 2019-11-12.
  5. ^ "E.164.3 : Principles, criteria and procedures for the assignment and reclamation of E.164 country codes and associated identification codes for groups of countries". www.itu.int. Archived from the original on 2019-11-12. Retrieved 2019-11-12.
  6. ^ URLs for Telephone Calls. IETF. April 2000. sec. 2.2. doi:10.17487/RFC2806. RFC 2806. Retrieved January 11, 2021.
  7. ^ Olsen, Chris (2011-08-01). Implementing Cisco Unified Communications Manager, Part 2 (CIPT2) Foundation Learning Guide: (CCNP Voice CIPT2 642-457). Cisco Press. p. 172. ISBN 9780132312141.
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