"ENUM 164" (also know as enum and e164) is a method that stores telephone numbers within the Internet's DNS. E164.org allows Voice over IP systems, such as Asterisk and SER (SIP Express Router), to place and receive telephone calls over the Internet, without using your local telephone line.

This allows businesses and people to make and receive telephone calls over the Internet and Internet style networks. Unlike other systems, your calls can be switched directly to the person you are calling instead of passing all of your calls through a single service provider. This means that congestion from busy services is reduced, providing a more reliable voice connection.

This system only requires a hostname to route phone numbers to, you can move around by simply updating a dynamic DNS service!

E164.org provides both "real" telephone and "free" number mapping to any Voice over IP address of your choosing. Presently we support multiple entries and multiple types, including IAX2, SIP, H323, TEL, HTTP, FTP, MAILTO, LDAP, ICQ, IRC, YAHOO, AIM and MSN! So if you applications can implement a DNS lookup on phone numbers you can effectively send faxes by email, email by phone number, find your friends on ICQ by their phone number, the possibilities are endless!"