Re: Disabling temporary addresses by default?

[Bob Hinden <[e-mail]>]

> On Jan 28, 2020, at 6:59 AM, Lorenzo Colitti <lorenzo=[e-mail]> wrote:
> 
> Changing subject because many participants are likely to just ignore yet another "SLAAC vs DHCPv6" thread. :-)
> 
> On Tue, Jan 28, 2020 at 11:27 PM <[e-mail]> wrote:
> In the context of 4941bis last call, it might be prudent of us to revisit this change:
> 
> https://tools.ietf.org/html/draft-ietf-6man-rfc4941bis-05#section-8
> 6.  Temporary addresses are *not* disabled by default.
> 
> Saying that temporary addresses should be disabled by default (assuming hosts actually do that) seems like a terrible privacy problem. It means that by default, a host that doesn't change prefix will use the same IPv6 address to communicate with *everyone* on the internet until the end of time. That provides lots of opportunities for cross-site tracking, and the user can do very little to protect themselves because they don't have control over IP addressing like they do over higher-layer identifiers (e.g., users can clear cookies, or use different browser profiles or different browsers/apps for different sites).
> 
> I don't think 4191bis should advance if it says that privacy addresses are disabled by default. It would be a strong statement by the IETF that we don't care about privacy of IP addresses and would be a terrible signal to send.

I agree.

> Instead of disabling, why not change the default of the number of addresses maintained? For example, instead of maintaining 1 permanent + 1 valid + 7 deprecated, why not just default to maintaining 1 permanent + 1 valid + 1 deprecated. That means that applications would have to re-establish their connections once a day instead of once every 7 days. But if they use privacy addresses, they already need to re-establish connections after 7 days. And they can always use not to use privacy addresses via the appropriate socket option.

If the concern with privacy addresses is that a node might have a large number of these addresses, then this seems reasonable to me.

Bob