North American Network Operators Group
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Re: EU Official: IP Is Personal

  • From: Roland Perry
  • Date: Fri Jan 25 08:03:58 2008

In article <[email protected]>, Andy Davidson <[email protected]> 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.

Apologies, I should have made it clear that I was following up the remark about cellphone number portability. Described in 2002 (at the beginning of the discussion about migrating to the new system that's currently still being built):

"To deliver a call a routing enquiry is made to a Home Location Register (HLR) to determine where the subscriber is located and to obtain a routing number. The solution for mobile number portability, known as the Signalling Relay Function (SRF), is that the donor network sends the routing enquiry signal addressed to a ported number to the appropriate recipient network for treatment. In this way the recipient network can provide the routing number to complete the call."

Although that is also apparently known as "onward routing", even though the subsequent call traffic isn't routed onwards.
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Roland Perry