ENUM and SIP

I've decided that I need to understand this in detail, very soon. I don't yet get all the implications, especially in combination with IPv6. ENUM is more or less a registry translation service done by an interesting Quango (Handy UK term - what's that mean?) called Neustar. Here is their whitepaper on ENUM -- I need to find similar discussions of SIP, process, and blog it here. To be continued.