[ipv6hackers] Dynamic prefixes & privacy (was: IPv6 prefix changing)

Markus Reschke madires at theca-tabellaria.de
Thu Mar 15 15:23:25 CET 2012

On Thu, 15 Mar 2012, Alex List wrote:

Hello Alex!

> Do you mean that if prefixes were at least as random as IPv4 addresses
> and privacy extensions were in place, then marketing companies would
> need to rely on webbrowser-based methods?

Not exactly, but yes. IPv6 privacy extensions alone would be sufficient to 
make IP based tracking a lot harder and too inaccurate for the marketing 

There's only a very low randomness of IPv6 prefixes and IPv4 
addresses in the real world. Each access router has some IPv4 subnets 
and some larger IPv6 subnets assigned too. Out of those prefixes each 
customer gets an IPv4 address and/or an IPv6 prefix. The goal is to have 
as less routing entries as possible in your network. If an ISP would 
assign IP addresses/prefixes randomly across the whole network there would 
be a lot of trouble with the converging of dynamic routes. The randomness 
is limited to the size of the fixed prefixes of the access router.

What does that mean for our marketing company? With some geo-location 
(also whois and DNS reverse mapping) it can find out which prefixes of a 
specific ISP are used in an area. The customers of that ISP in that area 
will always have an address/prefix inside the same prefixes. oops :-)

/ Markus Reschke \ / madires at theca-tabellaria.de \ / FidoNet 2:244/1661 \
\                / \                             / \                    /

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