[LINK] RFI: Geolocation based on IP-Address
gdt at gdt.id.au
Thu Sep 27 10:17:18 EST 2007
On Thu, 2007-09-27 at 08:44 +1000, Roger Clarke wrote:
> I've finally made time to look at http://www.ip2location.com/free.asp.
> It gets me right, at the level of 'ACT' (except for "Net Speed: DIAL").
> I'm unclear how the service can narrow it to the ACT.
There are a few ways:
- you can look at the allocation data
- you can take the routing information from route-views
and reduce it to countries using some clever inferences
about international links
The more professional services then manually adjust where the
network topology doesn't match the geographical topology
(eg, where two Australian ISPs exchange data in the USA).
Note that these services aren't exact. So they are no good
for regulatory compliance uses. But they are fine for
setting defaults, such as determining if you should be
presented with example.com/example.com.au/example.de.
Sometimes you want the network topology anyway: such as
when you want to present someone with their nearest
mirror site or content distribution node. That's
done using a BGP feed from each mirror/node or by
inferring the network topology from echo times.
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