On Fri, Jan 25, 2008 at 10:42:44AM +0000, Roland Perry <lists@internetpolicyagency.com> wrote a message of 15 lines which said:
in the UK it [phone number portability] 's done with something similar to DNS. The telephone system looks up the first N digits of the number to determine the operator it was first issued to. And places a query to them. That either causes the call to be accepted and routed, or they get an answer back saying "sorry, that number has been ported to operator FOO-TEL, go ask them instead".
What happens when a phone number is ported twice, from BAR-TEL to FOO-TEL and then to WAZ-TEL? Does the call follows the list? What if there is a loop? The solution you describe does not look like the DNS to me. A solution more DNS-like would be to have a root (which is not an operator) somewhere and every call triggers a call to the root which then replies, "send to WAS-TEL".