[LINK] RFI: Geolocation based on IP-Address

[Paul Brooks]

David Lochrin wrote:
> On Thursday 27 September 2007 13:10, Paul Brooks wrote:
>   
>> In a service using Telstra Wholesale Layer2 ADSL, the IP address is
>> allocated by the ISP, not by Telstra.  Interconnect is in the capital 
>> cities, so usually it will be in state-based blocks - a particular
>> address might allocated to someone anywhere within ACT, while a
>> Brisbane-based IP address might be re-allocated to another service
>> anywhere in QLD, but not Canberra.
>>     
>
> So packets (PPPoE?) go all the way back to the ISP's nearest router in order to begin the routing process?
Yes
>   Or does Telstra allocate an IP address at the local exchange from the ISP's subnet on behalf of the ISP?  This is something I've never been sure about.
>   
No :-)
> If the former and the ISP only has a point of presence at their head office, then all packets must be routed via there, even if the end-points are 100 metres apart on the other side of the country?
>   
Yep, thats the way it works. An ISP can only interconnect with the 
Telstra Wholesale ADSL platform at a couple of capital city exchanges in 
each state. The PPPoE protocol sets up a tunnel from your house back to 
the capital city interconnect for the packets to travel through. If both 
you and your neighbour in a country town connect to the same ISP (or 
even different ISPs) then packets between you will travel to the nearest 
capital city on your PPPoE tunnel, through the ISP's router, and then 
back again on your neighbour's PPPoE tunnel.

Yet another example where Internet topology and packet travel path may 
have little resemblance to geography.

Paul.