Enum Tutorial

What is ENUM?

ENUM is the convergence of communications technologies into one architecture. ENUM is a simple, but powerful protocol that maps numbers to Internet domain names. ENUM was developed to provide an input mechanism for a twelve-key telephone to access the Internet.

By using the domain name system (DNS), a single number can be used for multiple communications technologies such as telephone, email, fax, text and voice messaging, web sites and more. ENUM promises easy and unified communication, no matter which network or device is used.

Key Benefits

ENUM is set to revolutionise the telecommunications industry, and goes hand-in-hand with technologies such as Voice over Internet Protocol (VoIP). There are 3 key benefits of ENUM:

A Unified Address

It is now common to originate telephone calls from IP based networks such as the internet. Calls are usually direct to other IP users, or they are terminated via the PSTN at a cost to the user. PSTN users, however, cannot yet connect to an IP network without special VoIP equipment.

In order to contact a user on an IP network from the PSTN, a global addressing standard is required - a standard that works across both IP networks and PSTN. The answer? ENUM.

ENUM domains can be used as a unified communications address in place of:

• Telephone number
• Mobile phone number
• Fax number
• Email address
• Messaging addresses (msn, yahoo, icq etc.)
• Web site URI
• Many more

This has obvious benefits; Imagine your business card with an ENUM instead of all the above.

Lower costs

The only requirements to use ENUM services are:

1. Your ENUM registration with a registrar such as Instra.
2. DNS hosting (provided free with registration)
3. Internet connection
4. IP or PSTN communication device (softphone, telephone etc.)

Calls using ENUM are routed over the internet, and therefore substantially reduce costs. While savings can already be made by using VoIP, ENUM allows for the use of regular PSTN telephones without the cost of special VoIP equipment.

Easy communications management

ENUM gives users the power to control their own communications. Utilising a system similar to the current domain name system, users can redirect and manage all of their communication devices from one control panel.

ENUM also differs from traditional communication services because the numbers are completely portable. There is no reliance on a particular ISP or telco, and there is no reliance on a device such as a telephone or fax machine. The only requirements are an ENUM registration and a name server to host your ENUM (you could even host it yourself).

Technical Overview

In simple terms, an ENUM communication begins as a number that could, for example, be dialled into a telephone. The request is then converted to a domain name, and routed over the Internet to the appropriate communications device at the receiving end. ENUM routing can be broken into 4 steps as follows:

1. Remove all non-digit characters from the input string. Example:
   "+61.397831800" produces "61397831800"
2. Place dots (".") between each digit. Example:
   6.1.3.9.7.8.3.1.8.0.0
3. Reverse the order of the digits. Example:
   0.0.8.1.3.8.7.9.3.1.6
4. Append the string ".e164.arpa" to the input. Example:
   0.0.8.1.3.8.7.9.3.1.6.e164.arpa

From this point, ENUM works in the same way as a domain name, using the DNS. When the communication request finds the authoritative name server for the ENUM domain, the associated zone file uses NAPTR records to direct the communication request to the appropriate service.