Re: 64bit MAC addresses and SLAAC

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 <bob.hinden@gmail.com> wrote:

> Alexandre,
>
> > On Jun 17, 2020, at 4:39 AM, Alexandre Petrescu <
> alexandre.petrescu@gmail.com> wrote:
> >
> > Le 15/06/2020 à 23:01, Bob Hinden a écrit :
> >> Alexandre,
> >>> On Jun 15, 2020, at 1:23 PM, Alexandre Petrescu <
> alexandre.petrescu@gmail.com> 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