Re: 64bit MAC addresses and SLAAC

[Bob Hinden <[e-mail]>]

Etienne,

Good to hear that SLACC requires less energy than IPv4 automatic address configuration.

I agree it is a tradeoff when privacy is needed or not.  I suspect that if the calculation to generate a random number is only done very occasionally or only on boot-up, I would think that the energy required isn’t very significant over time.

Bob


> On Jun 17, 2020, at 10:23 AM, Etienne-Victor Depasquale <[e-mail]> wrote:
> 
> Bob,
> 
> In the case of resource-constrained nodes, such as wireless sensor networks (WSNs),
> the use of algorithms to generate addresses consumes energy.
> 
> In my lectures to date (I'm an academic),
> I've emphasized that SLAAC in IPv6
> requires less energy than automatic address configuration in IPv4.
> 
> RFC7217's method of address generation seems to load WSNs unnecessarily,
> unless the identity of a sensor is somehow considered important.
> 
> Etienne
> 
> On Wed, Jun 17, 2020 at 6:37 PM Bob Hinden <[e-mail]> wrote:
> Alexandre,
> 
> > On Jun 17, 2020, at 4:39 AM, Alexandre Petrescu <[e-mail]> wrote:
> >
> > Le 15/06/2020 à 23:01, Bob Hinden a écrit :
> >> Alexandre,
> >>> On Jun 15, 2020, at 1:23 PM, Alexandre Petrescu <[e-mail]> wrote:
> >>> Hi,
> >>> Before the sanitary situation I was studying an issue at ISO.
> >>> The issue is about 64bit MAC addresses and SLAAC.
> >>> SLAAC needs a 48bit MAC addresses in order to work, and it can not work with a 64bit MAC address; (but yes, it can with 64bit IIDs).
> >> SLACC does not specify the length of the Interface ID, it does not require require 48-bit MAC addresses, and the reason for Modified EUI-64 Format Interface Identifiers in RFC4291 was to support 64bit EUI-64 Identifiers.   We have since moved away from using MAC addresses as Interface IDs.  See RFC 8064.
> >
> > Bob,
> >
> > RFC8064 says "this document [...] recommends against embedding stable
> > link-layer addresses in IPv6 Interface Identifiers”.
> 
> The actual text is:
> 
>    By default, nodes SHOULD NOT employ IPv6 address generation schemes
>    that embed a stable link-layer address in the IID.
> 
> It is more than a recommendation.
> 
> >
> > But a 64bit MAC address could be a random number as well, not
> > necessarily stable.  Windows randomizes some of its MAC addresses.
> 
> RFC7721 discusses this, along with what Windows does.
> 
> >
> > That aside, I am not sure how much RFC8064 is clear about the length of
> > an IID (it refers to RFC7217 '_could_ any len'), neither am I sure how
> > much is it implemented (linux and freebsd implement random IIDs but of
> > fixed length).
> 
> The length of an Interface ID is not defined in RFC8063.  That is a bigger topic, the current specification is RFC4291 as updated by RFC5952, RFC6052, RFC7136, RFC7346, RFC7371, and RFC8064.
> 
> Bob
> 
> 
> >
> > Alex
> 
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> --
> Ing. Etienne-Victor Depasquale
> Assistant Lecturer
> Department of Communications & Computer Engineering
> Faculty of Information & Communication Technology
> University of Malta
> Web. https://www.um.edu.mt/profile/etiennedepasquale