One of the reasons that I was late to VoIP was that the initial services just weren’t that exciting. (To be fair to myself, I probably wasn’t really that late. I just feel like it sometimes because so many of my friends were first-wave early adopters.) Another way to connect up to a regular phone number was certainly interesting, but after having been a world-traveling GSM subscriber for years, the idea of getting a number that followed me around the globe really wasn’t earth-shattering.
VoIP is much more interesting when you can find ways of supplanting the telephone network instead of attaching to it. I recently signed up for an Internet Telephony Administrative Domain (ITAD) number. ITADs come to us from RFC 3219, and were originally intended to be part of an alternative telephone routing scheme. However, they’ve been re-purposed as a generic “Internet-style” telephone number.
Like an e-mail address, an ITAD Subscriber Number (ISN) consists of two parts. Within a realm, each user is assigned a unique number. The two are then joined with an asterisk, so that user number 123 in ITAD 456 would be addressed as 123*456.
If you’d like an ITAD number of your very own, there’s a short cookbook with instructions that take you from wanting a number to being globally reachable. When I applied to IANA, I had a response from them in one business day. (Unfortunately, I was busy traveling and sat on it for a few days. If I’d been able to respond promptly, I might have had a lower number than they do!)
If you’re running a PBX and want to call me, or more likely, somebody at one of the other ITAD-enabled organizations, it’s worth it to sign up. The cookbook has instructions for advertising your reachability in DNS, and there’s a project-run DNS server that you can use if you don’t have access to a DNS server that supports naming authority pointer (NAPTR) records. When I wrote to get my ITAD number added into that server, I had a response in less than eight hours, even though I submitted my request on a Sunday.