On Wed, Aug 18, 2010 at 12:34 PM, Mark Smith wrote:
Haven't really thought about it before.
One thing to consider is that unless the preferred and valid lifetimes of an IPv6 prefix are set to infinity, IPv6 prefixes are always dynamic - they'll eventually expire unless they're refreshed. The preferred and valid lifetimes for prefixes that are delegated to customers could be something that they might be able to change via a web portal, bounded to within what you as an ISP are happy with e.g. 1 to 30 days, rather than the absolute range of lifetime values supported. CPE could also potentially do the same thing with the range of subnets it has been delegated, by phasing in and out subnets over time on it's downstream interfaces. (The more subnets the better, so a /48 would be ideal for this.)
Yep, I am in favour of such setups. This will stress internal name services(eg. netbios) but would be a solvable problem, I think.
As you've mentioned, privacy addresses help. A related idea is described in "Transient addressing for related processes: Improved firewalling by using IPv6 and multiple addresses per host." [0], Peter M. Gleitz and Steven M. Bellovin, which takes advantage of the 2^64 addresses in a /64, and has different applications on the same host use different source IPv6 addresses.
Pretending to be multiple hosts, or even just one with privacy addresses, moving around multiple subnets, on delegated prefixes that change fairly regularly would probably mitigate quite a lot of the privacy concerns people may have related to IPv6 addressing.
If your ipv6-geolocation-service tells you that all /48 prefixes behind this network are just static home-user networks, why not just ignore the lower 64 bits or even the lower 80 bits? Privacy extensions would be no help here. In IPv4-land I have the possibility to reconnect and get a new unrelated ip-address every time. hannes