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ENUM was developed as a solution to the question of how network elements can find services on the Internet using only a telephone number, and how telephones, which have an input mechanism limited to twelve keys on a keypad, can be used to access Internet services. ENUM at its most basic is the convergence of PSTN and IP networks; it is the mapping of a telephone number from the public switched telephone network to Internet functionalities.
"ENUM" has a number of meanings. It is the name of a protocol that resolves fully qualified telephone numbers to fully qualified domain name addresses using a DNS-based architecture. It is the name of a chartered working group of the Internet Engineering Task Force (IETF) chartered to develop protocols that map telephone numbers to resources found on the Internet using the Domain Name System. It is also the title of RFC 2916, the approved protocol document that discusses the use of DNS for the storage of E.164 numbers and the available services connected to an E.164 number.
ENUM does not change the Numbering Plan and does not change telephony numbering or its administration in any way. ENUM will not drain already scarce numbering resources because it uses existing numbers.
How do make ENUM calls?
Once a telephone number is entered, it is translated into an Internet address using the following steps:
The phone number is translated into a fully qualified E.164 number by adding the city (or area) and country code. Example: 555-1234 dialed in Washington, DC becomes +1-202-555-1234, where the "1" represents the North American country code. The "+" indicates that the number is a fully qualified E.164 number.
All characters are removed except for the digits. Example: 12025551234
The order of the digits is reversed. Example: 43215552021
Dots are placed between each digit. Example: 4.3.2.1.5.5.5.2.0.2.1
The domain "e164.arpa" is appended to the end. Example: 4.3.2.1.5.5.5.2.0.2.1.e164.arpa
ENUM then issues a DNS query on this domain. Once the authoritative name server is found, ENUM retrieves relevant NAPTR Resource records and will perform according to the user's registered services for that number.
Posted by george99
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