Public Enum and the state of VoIP
"Islands" of VoIP
The improved access to VoIP communication has been fueled by an increased Internet penetration throughout the world as well as improved bandwidth speeds across the board. While at one point of time VoIP used to be seen as a bandwidth hog, it's not even a blip compared to the Internet speeds available to the average user in the developed world.
However, one issue is still blocking VoIP from really taking off. As of now VoIP stands on its merits. It's cheaper, provides more functionality and is far more flexible than PSTN systems. However, the majority of calls still either originate from or go to a PSTN line and so even VoIP users have to pay for that part of the call which travels over the regular phone lines.
Nevertheless, even when VoIP calls are made to another VoIP provider using a telephone number, the call still travels over PSTN! This is because given the way the system is set up, we use phone numbers to call each other and there's no easy way to tell whether a particular number is VoIP based and if so, what the target device's address is. This leads to "islands" of VoIP where each provider's subscriber base sits alone and can't touch the other islands without going through an expensive PSTN line.
To solve this problem, we can easily build a system which keeps track of which numbers are VoIP ones and if so, what their "real" SIP addresses are. Each SIP business VoIP service will subscribe to this directory and include their own range of telephone numbers which have been allotted to them by the telco along with the full SIP URI.
So before making a call, each VoIP phone will lookup this universal directory, see whether or not it's actually an SIP address and if so, make the call directly over the Internet without dropping down to the phone network! Such a system will greatly reduce the cost of VoIP calls even further and deliver better service like HD Voice to boot via a customer's hosted SIP proxy server.
Unfortunately, public ENUM is yet to take off in the US. Legislation enabling it is moving at a snail's pace and isn't helped by the reluctance of the various carrier's to the move since it cuts them out of the loop entirely. However, it's just a matter of time before this happens in one way or another. Soon smartphones might begin to have functionality that stores the SIP URI along with the person's phone number and makes the appropriate type of call depending on the circumstances. We can only hope that day comes sooner rather than later!