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.
| The international public telecommunication numbering plan | |
| Status | In force |
|---|---|
| Year started | 1984 |
| Latest version | June 2020 |
| Organization | ITU-T |
| Committee | Study Group 2 |
| Related standards | E.123, E.163 |
| Domain | telephony |
| Website | https://www.itu.int/rec/T-REC-E.164/ |
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. 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 E.163 was withdrawn, and some recommendations were incorporated into revision 1 of E.164 in 1997.
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. 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.
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. 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 | |
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 with the telephone country code. This is called the globalized format of an E.164 number, and is defined in the Internet Engineering Task Force RFC 2806. The international calling prefix is a trunk code to reach an international circuit in the country of call origination.
DNS Mapping of E.164 numbers
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
- Carrier of Record
- E.123
External Sources
- ITU National Number Plans Reference
References
- "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.
- "E.163 : Numbering plan for the international telephone service". www.itu.int. Archived from the original on 2019-07-29. Retrieved 2019-11-12.
- "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.
- "E.164.2 : E.164 numbering resources for trials". www.itu.int. Archived from the original on 2019-11-12. Retrieved 2019-11-12.
- "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.
- URLs for Telephone Calls. IETF. April 2000. sec. 2.2. doi:10.17487/RFC2806. RFC 2806. Retrieved January 11, 2021.
- 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.
External links
- Text of the Recommendation, Amd. 1 and supplement 6 (E.164)
- List of ITU-T Recommendation E.164 assigned country codes as of 15 December 2016
- List of ITU-T Recommendation E.164 Dialling Procedures as of 15 December 2011
- Numbering plan for the international telephone service (E.163) (incorporated in E.164)
- World Telephone Numbering Guide
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 Recommendation ITU T E 164The international public telecommunication numbering planStatusIn forceYear started1984Latest versionJune 2020OrganizationITU TCommitteeStudy Group 2Related standardsE 123 E 163DomaintelephonyWebsitehttps www itu int rec T REC E 164 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 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 EraRecommendationsE 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 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 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 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 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 formatsThe 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 Number1 to 3 digits maximum 15 digits number of digits in the country codemaximum 15 digitsGlobal services Country Code Global Subscriber Number3 digits maximum 12 digitsmaximum 15 digits Figure 2 Networks Country Code Identification Code Subscriber Number3 digits 1 to 4 digits maximum 12 digits number of digits in the identification codemaximum 15 digitsGroups of countries Country Code Group Identification Code Subscriber Number3 digits 1 digit maximum 11 digitsmaximum 15 digitsTrials Fixed code Trial Identification Code Subscriber Number991 1 digit maximum 11 digitsmaximum 15 digitsUses of E 164 numbersE 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 with the telephone country code This is called the globalized format of an E 164 number and is defined in the Internet Engineering Task Force RFC 2806 The international calling prefix is a trunk code to reach an international circuit in the country of call origination DNS Mapping of E 164 numbers 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 1999 555 0123 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 alsoCarrier of Record E 123External SourcesITU National Number Plans ReferenceReferences 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 E 163 Numbering plan for the international telephone service www itu int Archived from the original on 2019 07 29 Retrieved 2019 11 12 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 E 164 2 E 164 numbering resources for trials www itu int Archived from the original on 2019 11 12 Retrieved 2019 11 12 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 URLs for Telephone Calls IETF April 2000 sec 2 2 doi 10 17487 RFC2806 RFC 2806 Retrieved January 11 2021 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 External linksText of the Recommendation Amd 1 and supplement 6 E 164 List of ITU T Recommendation E 164 assigned country codes as of 15 December 2016 List of ITU T Recommendation E 164 Dialling Procedures as of 15 December 2011 Numbering plan for the international telephone service E 163 incorporated in E 164 World Telephone Numbering Guide
