Glossary
fThis glossary explains the main terms associated with ENUM. The terms are listed in alphabetical order.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
DNS-service provider
A DNS service provider manages name servers for the ENUM DNS zones where the NAPTR records are stored. There is a direct relationship between the DNS service provider and the registrant and registrar. The registrant will often delegate technical management of his/her ENUM zone to a DNS service provider. When a registration application is made, the registrar has the task of checking whether the DNS service provider satisfies the technical requirements. In many cases, the registrar and the DNS service provider will be the same party; sometimes the registrant and the DNS service provider will also be the same party, but they will often be quite separate.
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ENUM
Electronic Numbering, the general name for ENUM applications.
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ENUM NL
The registry that manages the Dutch ENUM zone.
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E.164.arpa
The dot-arpa top level domain (TLD), which is appended to the reversed phone number enabling it to be used on the internet. Dot-arpa is much like other TLDs, such as dot-NL and dot-com, but (in combination with e164) is used only for ENUM applications.
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E.164-number
Every phone number in the world is structured according to a global standard: the e164 number plan of the ITU (International Telecommunications Union). E.164 numbers contain up to fifteen digits preceded by a "+" (representing the international access code). Each number starts with the country code for the country it belongs to.
To call an (international) E.164 phone number from a landline, the caller first has to dial the international access code. This code differs depending on the country that the call originates from. From the Netherlands, the international access code is "00".
Although it isn't apparent to the user, ENUM works with phone numbers in reverse order. This is because domain names are hierarchically arranged from right to left, while phone numbers are structured the other way around. By reversing a phone number and adding ‘e164.arpa', you get a domain name that can be used on the Internet or, in fact, on any IP network. So the (fictitious) Dutch phone number +31 (0) 20 123 4567 becomes 7.6.5.4.3.2.1.0.2.1.3.e164.arpa.
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Geographical numbers
Geographical numbers are phone numbers that are linked to fixed phone lines (landlines) and include a dialing code that relates to a particular place or region (e.g. ‘030' for Utrecht and ‘0183' for the Arkel area).
Not all phone numbers have a geographical basis. There are also non-geographical numbers, most of which are reserved for certain types of service or special purposes. Non-geographical numbers used in the Netherlands include:
00 international access number
06 mobile numbers and pager services
0676 Internet providers
0800 charge-free information numbers
082 virtual private networks
084, 087 personal assistance services
085, 091 national dialing codes
088 business numbers
0900, 0906, 0909 premium information numbers
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ITU (International Telecommunication Union)
Global treaty organisation, which is part of the United Nations and through which members states make agreements regarding international telecommunications policy. The organisation seeks to facilitate International cooperation between member states, to assist developing countries, to improve the efficiency of telecommunications and to harmonise telecommunications.
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The Domain Name System (DNS) is the main system and protocol used by the Internet community to convert domain names into IP addresses and vice versa.
A DNS server or Domain Name Server makes conversions on the basis on this protocol, thus enabling computers to be approached using their (impractical) IP addresses and their host names (computer names). The opposite (reverse DNS, the conversion of IP addresses into host names) is also possible.
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NAPTR records
NAPTR stands for Naming Authority Pointer. This is a DNS record in the zone file of a domain, which includes access information specified in accordance with RFC 3403.
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NLEG
The Netherlands ENUM Group: a group of organisations chaired by the Ministry of Economic Affairs, which for the last few years has been working the pave the way for the introduction of ENUM to the Netherlands.
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Number holder
A number holder is a party that, directly through OPTA, has control of a phone number or a block of numbers. The number (block) may be for the subscriber's own use (e.g. a mobile or geographical phone number) or for assignment to a telephony service ender user (e.g. 0900 numbers)
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Number subscriber
A number subscriber is the person or organisation that has use of a phone number that is included in the Netherlands' number plan. An ENUM domain name can be registered only to the corresponding phone number's subscriber.
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Registrant
An ENUM registrant is the party to whom an ENUM domain name is registered. The registrant decides how the domain name is registered (through which registrar and using which name servers) and what pointers (NAPTR records) are included in the zone file. The registrant of an ENUM domain name must always be the corresponding phone number's subscriber.
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Registrar
A registrar is a party that registers ENUM domain names with ENUM NL on behalf of number subscribers. If a number subscriber wishes to apply for an ENUM registration, the subscriber has to select an ENUM registrar to act on his/her behalf. The registrar acts as an intermediary between the number subscriber and ENUM NL; number subscribers cannot register domain names with ENUM NL directly.
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Registry
The registry manages the ENUM zone and the relevant country's authoritative name servers. The Netherlands' registry is ENUM NL, which manages the name servers for the 1.3.e164.arpa zone.
The registry registers ENUM domain names within its domain, and enters delegations to the relevant zones in the DNS.
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Every ENUM domain name is derived from an e.164 phone number. Before an ENUM domain name can be registered, a check has to be made to verify that the prospective registrant is also the subscriber to the corresponding e.164 phone number. Once the name has been registered, the check has to be repeated every so often. This checking process is referred to as validation, and a party that performs such checks is a validation agent.
Different validation agents use different validation methods. A mobile phone number, for example, can be validated by means of SMS authentication. Where a geographical number is concerned, confirmation from the relevant telephony service provider may be sufficient.
A registrant is free to choose which validation agent to use (perhaps on the basis of advice from his/her registrar). In many cases, registrars themselves act as validation agents, so there is no need to involve a third party.
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Validation agent
A validation agent is an organisation that verifies that the party applying to register an ENUM domain name is indeed the corresponding phone number's subscriber. Various parties may act as validation agents; validation does not have to be performed by one particular body. Various validation methods may be used, depending on the circumstances. A number holder may, for example, use an internal method to validate its own numbers, while applications from outside parties require validation by means of call-back or SMS confirmation.
NB: The validation methods referred to are purely illustrative.
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