Re: 6MAN WG Last Call: <draft-ietf-6man-ug-01.txt>

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

On 23/07/2013 09:12, Mark ZZZ Smith wrote:
> Hi,
> 
> Firstly, I support advancing this draft.
> 
> Some suggested changes:
> 
> "  This has no known harmful effect as long as the
>    replicated MAC addresses and IIDs are used on different layer 2
>    links.  If they are used on the same link, of course there will be a
>    problem, to be detected by duplicate address detection [RFC4862], but
>    such a problem can usually only be resolved by human intervention."
> 
> I think it would be worth pointing out that the link layer is most likely to fail to operate with duplicate link layer addresses, before DAD has a chance to detect duplicate IPv6 addresses.

OK.

> 
> "  Also, there is
>    evidence from the field that IEEE MAC addresses with "u" = 0 are
>    sometime incorrectly assigned to multiple MAC interfaces.  Firstly,
>    there are recurrent reports of manufacturers assigning the same MAC
>    address to multiple devices. Secondly, significant re-use of the
>    same virtual MAC address is reported in virtual machine environments. "
> 
> I found this text a bit confusing. The '"u" = 0' term read like it was referring to locally unique IEEE MAC addresses ("unique equals no"), and then the 2nd sentence is referring to globally unique (but duplicated and therefore not actually globally unique) MAC addresses, u = 1 in an IPv6 IID, the opposite of what the previous sentence was referring to. Then the third sentence seems to be describing to what the first sentence was referring to. I think the cause of the confusion might be that IEEE use the "locally assigned" bit to distinguish locally generated or not (i.e., "l" = 0 for globally unique), where as IPv6 IIDs have renamed it to "u" bit when the value is inverted. I'd suggest trying to ensure the IEEE terminology is used when IEEE addresses are discussed to make it clearer what the properties of the IEEE address are.

Yep. I remember complaining when the bit inversion was first proposed
that it would lead to years of confusion. Which IEEE standard is the
basic reference for their terminology?

    Brian