ENUM

ENUM – Telephone Number Mapping – is a protocol that links traditional telephone numbers to Internet services.

ENUM

ENUM is an Internet database in which phone number owners publish information on how others can call them via the Internet. It is a global system in which each country has a registry administrator for numbers with the corresponding national prefix.

The CZ.NIC Association manages the ENUM registry for numbers in the Czech Republic (numbers with the international prefix +420).

Domain registration itself is handled by registrars. These registrars have access to the registry and enable their customers to register and manage their phone numbers.

Registrars that support ENUM:

How does ENUM work

ENUM is an implementation of a standard RFC3761 , which specifies how to associate information about Internet services with a regular phone number. ENUM specifies how numbers in the form of E.164 (regular phone numbers) converted to domain names, and how data on the Internet services associated with a given phone number will be stored for those domains. All of this is done using the well-known and proven DNS (Domain Name System), which is used to assign IP addresses to domain names on the Internet.

ENUM is most commonly used for IP telephony (VoIP - Voice over Internet Protocol), when a SIP address is added to a phone number in the DNS so it can be used to place a call to that phone number over the Internet. The process of storing this information in the DNS is as follows:

Enter a phone number in international format: +420 234 567 890

The number is stripped of any extra non-numeric characters and spaces: 420234567890

The order of the digits will be reversed, and periods will be inserted between the digits: 0.9.8.7.6.5.4.3.2.0.2.4

The system's ENUM .e164.arpa global domain suffix is added: 0.9.8.7.6.5.4.3.2.0.2.4.e164.arpa

By following these steps, we will obtain a domain name in the form of 0.9.8.7.6.5.4.3.2.0.2.4.e164.arpa. We will store the domain created in this way in the DNS, in a special record (NAPTR), SIP address in URI form, i.e. sip:uzivatel@domena (e.g. sip:jan.dvorak@firma.cz). When a query is then made for the domain name, the relevant DNS server returns a response containing the SIP address, which can then be used to establish a call via VoIP.

ENUM is a global system that is organized under the e164.arpa domain, with each country having its own national ENUM domain in which all numbers in that country are registered. This national domain consists of the country's national telephone code.

Czech Republic has domain 0.2.4.e164.arpa.