Re: [dhcwg] Last Call: <draft-ietf-dhc-anonymity-profile-06.txt> (Anonymity profile for DHCP clients) to Proposed Standard

[Brian E Carpenter <[e-mail]>]

On 13/02/2016 11:08, Christian Huitema wrote:
> On Friday, February 12, 2016 12:48 PM, Fred Templin wrote
>>> From: dhcwg [mailto:[e-mail]] On Behalf Of ???? (> JINMEI,
> Tatuya)
>>>
>>> Brian Carpenter called for an attention to Section 4.5.2 of the draft...
>>> so I'm responding to it.
>>>
>>> 4.5.2.  Prefix delegation
>>>
>>>    The interaction between prefix delegation and anonymity require
>>>    further study.  For now, the simple solution is to avoid using prefix
>>>    delegation when striving for anonymity.  When using the anonymity
>>>    profiles, clients SHOULD NOT use IA_PD, the prefix delegation form of
>>>    address assignment.
>>>
>>> I'm not sure what Brian tried to indicate in his message, but at least
>>> this section looks vague to me about the rationale for the "SHOULD
>>> NOT".  It's not obvious to me how IA_PD is worse than IA_NA in terms
>>> of privacy.  Is this a "SHOULD NOT" simply because the "interaction"
>>> (is not yet fully understood and) requires further study?
> 
> Yes, exactly that. There was some anxiety that prefix delegation requires
> understanding to whom the prefix is delegated. There are also potential side
> effects if prefix are reassigned quickly to random nodes. All that needs
> further study before we can make a recommendation. We can certainly add a
> bit of text to make that more clear.
> 
>> I don't have a strong opinion on the "SHOULD NOT" in this paragraph, but
> it is
>> very important that this guidance not be taken out of context. This
> document
>> is only about clients that wish to remain anonymous, which does not apply
> to
>> all use cases.
> 
> Yes. Also, we can add text explaining that once these problems are better
> understood and the IETF agrees on the proper way to handle anonymous prefix
> delegation, clients MAY use the agreed upon solution. Which is kind of
> redundant, but if you guys prefer it that way, why not.

To be clear, I don't have a strong opinion on this; it simply seemed like
something the IPv6 community should be aware of before it ends up in an RFC.
I also noticed this morning that it might impact draft-ietf-v6ops-host-addr-availability.

    Brian