Re: 6man w.g. last call for <draft-ietf-6man-default-iids-11.txt>

[Fernando Gont <[e-mail]>]

On 05/16/2016 01:25 PM, 神明達哉 wrote:
> 
>>> - clarify that this recommendation is only for environments where
>>>  address stability is needed
>>
>> The document says exactly this in the introduction:
>>
>> The recommendations in this document apply only in cases where
>>    implementations otherwise would have configured a stable IPv6 IID
>>    containing a link layer address.  That is, this document does not
>>    change any existing recommendations concerning the use of temporary
>>    addresses as specified in [RFC4941 <https://tools.ietf.org/html/rfc4941>], nor does it introduce any new
>>    requirements regarding when stable addresses are to be configured.
>>    Thus, the recommendations in this document simply improve the
>>    security and privacy properties of stable addresses.
> 
> This text specifically talks about RFC4941 as the "environments where
> address stability is NOT needed",

Please let me clarify this.

IPv6 nodes employ, by default, stable addresses. The only standardized
things that's different from that is temporary addresses, which
essentially specify how to generate temporary addresses *in addition* to
the stable ones.

If you want to do temporary-addresses-only, you need to update RFC4941,
because it says that you should have both stable and temporary addresses.

What we say in our document is: "where you'd configure a stable
addresses, do RFC7217 rather than embed link-layer addresses". We do not
argue whether you should have/use stable addresses in the first place.
Such requirements are elsewhere, and not in this document.


>  and, with the 'That is,' only talks
> about it.  On the other hand, my understanding of previous concerns in
> this context is to also cover other types of such environments,
> specifically the one using randomized link-layer addresses with the
> traditional algorithm of forming the IID from such LL addresses.
> 
>>From this one, and your response to the next point, it seems you are
> saying the decision was to refuse to address that concern.  Am I
> understanding it correctly?

No. My take is that the concern is flawed. Please read
draft-gont-predictable-protocol-ids, and even RFC4941, which talks at
length about security and privacy issues regarding reusing identifiers
in different context, for different scopes, etc.

Let's call a lemon a lemon: Asking to embed a layer-2 identifier/address
in a layer-3 address is extremely bad.

After 30+ years of experience with flaws related to improper selection
of numeric identifiers, it's really bad that people keep pushing this
sort of thing.


-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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