Re: [EXTERNAL] Re: 64bit MAC addresses and SLAAC

[Fernando Gont <[e-mail]>]

Hi, Pascal,

On 18/6/20 04:38, Pascal Thubert (pthubert) wrote:
> 
> There are cases where anonymity is entirely undesirable.

The key issue here is what the defaults should be. In the context of
RFC7258, I think it would be hard to make a case for privacy-insensible
algorithms for default configurations.



> Also +1 to Kerry. Some standards (including ours) can do a preferred
> treatment if the IPv6 address derives from the MAC. 

1) Embedding MAC adresses in IIDs is kind of a kludge. Yes, it made 
sense when borrowed from IPX ages ago... but the context was quite 
different.

2) From an interoperability standpoint, you should only rely on the IID 
being unique.


> Note that this
> looks antinomic with the spare part goal above; that would indeed be
> antinomic for burn-in MAC addresses; but there are also standards out
> there that use a shorter assigned MAC address, e.g., to reduce the
> frame size and save energy and bandwidth; in that case you can have
> both properties of deriving the IPv6 address from the MAC and
> replacing a failing device by a virtually identical one.

I don't mind when this sort of thing is employed for specific scenarios 
such as the one you describe. However, it would seem seem to me that if 
you really need the addresses to embed the underlying link-layer address 
so that you can compress the IPv6 header and keep the associated 
overhead at a decent level... one might (unfortunately) want to 
reconsider the extent to which IPv6 is really applicable here, or 
whether some sort of gateway that bridges a low-overhead simple protocol 
with the rest of the network might be a better approach.



> I support documenting pro/cons of address allocation behaviors, but I
> object constraining how people use IPv6, be it flow label, address
> format, routing headers and all, because of one's use case or
> religion. There are others.

RFC8064 makes a recommendation for the default algorithm for generating 
stable addresses. General purpose systems need some guidance recarding 
how to generate the IIDs, are what considerations should be had when 
developing such an algorithm.

As all "SHOULDs/SHOULD NOTs", it's okay to not follow the advice if you 
have really good reasons to and/or know better what you are doing.

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