My colleague Miguel posts on the recent launch of the Irish ENUM service Miguel Ponce de Leon: ENUM Services launched in Ireland. His posting gives the high level overview of what public ENUM is supposed to be, and how close this offering in Ireland is to delivering on this. The downside seems to be the requirement for a validation every six months with a fee that makes it more expensive to maintain a public ENUM entry than an Internet domain name registration.
In essence the public ENUM service links a telephone number to an IP address allowing the integration of Internet voice services and telephony. It is like a top level domain (TLD) for +353 (the international code of Ireland) in the same way that there is a TLD for .ie (the Internet country code domain for Ireland).
Interesting I discovered a while ago that there is a parallel movement, championed by the GSMA (the GSM Association of mobile operators) to create a private "on net" ENUM as an alternative to this public ENUM infrastructure. Note that in telecommunications speak "on net" means on the operators' private networks, i.e. not on the public Internet; logical from their perspective if a bit confusing at first if you are coming from an Internet perspective (what we normally think of as "the net").
Linguistic niceties aside, the potential problem with the open ENUM as illustrated by this Irish launch is that it is in effect publishing your telephone number for the world to see via an open database, so that potentially it could lead to similar problems of spamming that we see when email addresses are publicly exchanged.
The promise of the private ENUM, as an alternative infrastructure using similar technologies, is that your mobile operator will protect your privacy and only give the information to other valid operators (that could include Internet-based VoIP providers who have paid to be part of the scheme. They have ample experience of this type of information exchange between operators through the use of the roaming agreements that allow us all to make and receive calls and SMS text messages anywhere in the world. Whilst there has been some criticism of expensive roaming changes, everyone agrees it is an invaluable service.
I have noted before that I feel that it it is no coincidence that this solutions to the business problem of information exchange between operators arose in the European Union, a strange political beast where independent nation states have agreed to sacrifice some of their sovereignty in exchange for lasting pace and economic stability. It means we are constantly debating where the line between sovereignty and shared rules lies, and it places us in a good position to develop models that work where international boundaries need to be crossed, and everyone's opinions and rights need to be given due credit. Alternatively US and Chinese solutions tend to assume one size fits all, and are less likely to sit well with smaller countries jealous of their own ways of doing things. It takes all sorts of course, but I feel the EU has a lot to offer in developing working solutions for cooperating countries, legal systems, and shared critical infrastructures, such as the Internet and the telephone network, that cross these boundaries.