Nominet, the not-for-profit that runs the .co.uk domain name database, has been awarded the contract to build the new Enum registry. Enum domains will map telephone numbers to web addresses.

Enum is designed to get around the problem that few phone keypads have an "@" key, which makes dialling an SIP address for a VoIP call tricky. A VoIP user can be allocated a traditional phone number - technically an E.164, and anyone calling that number is connected to a gateway which then uses the Enum service to get an SIP address, and can then connect the call using the SIP protocol.

One day, of course, all our phones will be equipped with handy keyboards for entering SIP addresses properly, but until now we've been reduced to a plethora of proprietary solutions to this problem. Hopefully, the Enum registry will reduce the need for those, and make migrating SIP numbers technically easier.

To start with though, it's likely the registry will be used to link corporate VoIP systems and the various providers who currently have more informal interconnection agreements.

Nominet negotiated a change to its governance in November 2006 to allow it to operate more registries. Its explainer on Enum is here. ®

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