[v6ops] Alissa Cooper's Discuss on draft-ietf-v6ops-unique-ipv6-prefix-per-host-12: (with DISCUSS)

[Alissa Cooper <[e-mail]>]

Alissa Cooper has entered the following ballot position for
draft-ietf-v6ops-unique-ipv6-prefix-per-host-12: Discuss

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)


Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
for more information about IESG DISCUSS and COMMENT positions.


The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-v6ops-unique-ipv6-prefix-per-host/



----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------

I've put in a DISCUSS because I think the point I raise below warrants further
discussion, unless the WG already discussed it and concluded otherwise.

Section 7 says:

"However, when combining both IPv6 privacy extensions and a unique
   IPv6 Prefix per Host a reduced privacy experience for the subscriber
   is introduced, because a prefix may be associated with a subscriber,
   even when the subscriber implemented IPv6 privacy extensions RFC4941
   [RFC4941]."

If an operator assigns the same unique prefix to the same host every time the
host connects to the network, the unlinkability benefits of using IPv6 privacy
extensions are completely negated. It seems reasonable to me for this document
to normatively RECOMMEND that operators assign a different unique prefix to a
returning host for the purpose of limiting linkability to the lifetime of the
host's connection to the network. I'm sure there are exception cases where this
wouldn't make sense, and some examples of those could be given. But by default
this seems to me like a reasonable recommendation to mitigate the privacy risk
introduced by the unique prefix, while the attacks described in Section 1 would
also still be mitigated.

Did the WG discuss this?