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Cc: nanog@merit.edu From: Andy Davidson <andy@nosignal.org> To: Roland Perry <lists@internetpolicyagency.com> In-Reply-To: <nix4PU8k0bmHFARM@perry.co.uk> Date: Fri, 25 Jan 2008 11:36:34 +0000 Errors-To: owner-nanog@merit.edu On 25 Jan 2008, at 10:42, Roland Perry wrote: > In article <20080125093035.GH17698@hezmatt.org>, Matt Palmer <mpalmer@hezmatt.org > > writes >> Tunnels all over the place seems like the only way it'd even be >> halfway practical. It's more-or-less how phone number portability >> works anyway, from what (little) I know. > I don't know about the USA, but in the UK it'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". Not quite, the simplistic overview is that operators have an obligation to offer porting wherever practical, so operate ports on a accept-then-forward principal. If I port my number from CarrierA to CarrierB, then my calls still pass through A's switch, who transits the call to B without charging the end user. For the benefit of completeness, the regulator has mandated that this situation must change, as CarrierB's inward-port customers are not protected from the technical or commercial failure of CarrierA. The industry [www.ukporting.com] has responded and is building a framework to support all-call-query style lookups to handle number ports. Best wishes, Andy
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