The Quest for Seamless VoIP Connectivity
The Expectation of VoIP Intercommunication
I frequently see that people have different expectations from different pieces of technology even though there are no good reasons to do so. E-mail is a great example of a technology working without limitations. If you have a Gmail user account, there's no reason why you can't communicate with anyone who has an e-mail address regardless of what service they're using. You can have a corporate e-mail ID and have it completely interoperable with every single e-mail provider on the planet. That is one of its strengths. It's based on a shared standard protocol. The same functionality is expected of the PSTN system. You're supposed to be able to talk to anyone with a phone regardless of what carriers they work with.
When it comes to VoIP however, we have a strange blindness in not expecting the same. If you have a VoIP service with a given SIP provider, all calls to and from accounts that belong to the same provider are free – as they should be. This is very much like how a messaging service works within a company. However, if you then need to make a call to a person using any other VoIP provider, the call has to go over the PSTN system rather than over the Internet thereby incurring charges and ruining certain features of VoIP such as HD voice.
Creating a Shared Database
The above example is indicative of the many "islands" of VoIP on which we live. The ideal situation would be if VoIP works very much like e-mail and all communications between two users holding accounts with different SIP VoIP providers took place over the Internet in a transparent manner.
Unfortunately, we are held hostage to the tyranny of the phone number. The above scenario where smooth VoIP communications are a reality can happen only when people start dialing each other's SIP address instead of their telephone numbers. As of now, every VoIP user has a number that is a reference to their SIP URI. However there is no way to tell just by looking at it whether or not it hides an SIP URI behind it and what that URI is. For this, we need all VoIP providers to participate in a ENUM database that maps SIP telephone numbers to their appropriate SIP URI. Predictably however there is significant conflict in the business ecosystem preventing such a shared database from coming into existence. The large VoIP providers benefit from customer lock-in and would like to avoid a seamless VoIP environment as much as possible.
Personally I feel that technology cannot be stopped. It's only a matter of time before the barriers break down. When that happens, we would finally have broken from the PSTN system altogether.