The more Asterisk installations I do, the more I begin to realize how dumb it is to funnel each one’s calls out to the Public Switched Telephone Network (PSTN). As the number of VoIP phone systems grows, it makes sense to tie them together directly, rather than send them through the hundred-year-old technology which is the traditional telephone system. The glue that will bind all this together is called ENUM. ENUM is described in RFC-2916 as a way of including phone numbers in DNS records.
On a traditional PBX, the number an internal user dials is compared to a dialplan, parsed to determine if its a long-distance, local, or international call, and is then sent off appropriately. The call goes out through an expensive analog or digital T1 trunk to get where it is going, from originating PBX to the PSTN to the terminating PBX.
On an ENUM-enabled PBX, the dialplan first checks to see if the number can be looked up in DNS. If so, it uses the resulting IP address to send the call to the termination point over the Internet for free! The ENUM-enabled call goes from the originating PBX directly to the terminating PBX! No expensive trunks, no long-distance charges.
ENUM is not just for routing around expensive phone charges, however. It can be used to link a phone number to an email address, a website, instant messages. You name it! It opens the door to whole new ways of communication. Instead of dumbing down a sophisticated VoIP system to fit the creaky, century-old paradigm, ENUM sets it free.
I’m definitely going to learn more about this exciting new service.