phone fun, was GeoIP database issues and the real world consequences

Owen DeLong owen at
Wed Apr 13 20:52:13 UTC 2016

> On Apr 13, 2016, at 13:34 , Jean-Francois Mezei <jfmezei_nanog at> wrote:
> On 2016-04-13 16:18, Peter Beckman wrote:
>>  And further to that, throw in Local Number Portability (LNP) and you
>>  really need to know the full number in order to know which switch the
>>  specific number is assigned to. Not all 408-921 prefixed numbers will go
>>  to that switch in West San Jose.
> Is there the equivalent of BGP for number portability where every telco
> has the full table of who owns each prefix as well as individual routes
> for ported numbers ?

Sort of, but it’s called SS7 and it’s really more like multiple layers
of DNS than like BGP.

> Or is there a central database that is consulted before a dialed number
> starts to be connected so originating telco knows to send call ?

Well, yes and no, but AIUI, the common SS7 database is a lot more like
the DNS root zone.

> Or does the originating telco route the call to the original onwer of
> the prefix and lets that original owner figure out how to terminate the
> call ?

Generally within a country code (NANP is one country code even though it’s
many countries (US, CA, much of the Caribbean), the central SS7 database
will do a longest-match pointed to the correct Telco and possibly the
correct switch at that telco.

However, there are all kinds of different redirects possible within said
telco as well, such as call forwarding (in multiple forms), cellular
registration, VOIP gateways with portable SIP registrations, etc.

>> From a long distance billing point of view, if Bell Canada connects to a
> number originally onwed by AT&T but ported to Verizon, with whom would
> Bell share long distance revenues ?

Generally, Verizon. AT&T won’t usually participate in the call process at all.
(see above).


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