Re: [irtf-discuss] Why do we need to go with 128 bits address space ?

Mark Smith <markzzzsmith@gmail.com> Fri, 16 August 2019 07:26 UTC

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From: Mark Smith <markzzzsmith@gmail.com>
Date: Fri, 16 Aug 2019 17:26:40 +1000
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To: Fernando Gont <fgont@si6networks.com>
Cc: "Bless, Roland (TM)" <roland.bless@kit.edu>, shyam bandyopadhyay <shyamb66@gmail.com>, ietf@ietf.org, irtf-discuss@irtf.org, 6man@ietf.org
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Subject: Re: [irtf-discuss] Why do we need to go with 128 bits address space ?
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On Fri., 16 Aug. 2019, 16:59 Fernando Gont, <fgont@si6networks.com> wrote:

> On 16/8/19 09:02, Roland Bless wrote:
> > Hi Fernando,
> >
> > see below.
> >
> > On 15.08.19 at 20:13 Fernando Gont wrote:
> >> On 15/8/19 12:27, Roland Bless wrote:
> >> [....]
> >>> c) given the increasing number of virtual machines and IoT devices 64
> >>> bit isn't sufficient, see also the discussion of new MAC address
> lengths
> >> [...]
> >>
> >> The MAC addresses should have never been embedded in the IID. In fact,
> >> that's no longer the recommended way to generate IPv6 IIDs. See RFC8064.
> >
> > I guess you misinterpreted my statement, since I
> > was not referring to modified EUI64s or IIDs at all and I'm fully aware
> > of the RFC.
>
> Sorry for that!
>
>
> > This was just to point to IEEE work on extending the MAC address space,
> > showing the need for larger addresses and that 64-bit aren't obviously
> > sufficient, see e.g.,
> >
> https://www.ietf.org/proceedings/96/slides/slides-96-edu-ieee802work-0.pdf
>
> My friend John would say that MAC addresses are not addresses: They
> essentially are numeric IDs that are not topologically dependent (hence,
> not addresses), and that are required to be globally unique (most of the
> time, since you also have the U/L bit). The later can be convenient,
> also it is not really a requirement per-se.
>
> Assuming you could select a MAC address (well, "MAC ID") and detect
> collisions, you probably wouldn't need much more than, say 16-bit MAC
> addresses (unless you are really considering putting 65K devices on the
> same broadcast segment).
>

The story behind 48 bits when 10 bits would have done the job because of a
maximum of 1024 nodes, plus lots of other good discussion about flat and
hierarchical addressing in general.


"48-bit Absolute Internet and Ethernet Host Numbers", by Dalal and Printis,
Xerox, July 1981.
https://ethernethistory.typepad.com/papers/HostNumbers.pdf

>From Yogan Dalal's Ethernet History website:

https://ethernethistory.typepad.com/my_weblog/




> >From that perspective, you might argue that we could have done with
> 96-bit addresses (not to say 80-bit addresses, or less) -- alignment
> being a different business, of course. :-)  Or one could do
> variable-length addresses
>
> The specific 128-bit value seems to be a compromise between two
> proposals
> (
> https://www.lacnic.net/innovaportal/file/2578/1/ipv6-latnic2018-hinden-01.pdf).
> ..
> but I won't speak for Bob. ;-)
>
> P.S.: Of course the ship has already sailed. So other than for the sake
> of Internet history or the sake of discussion :-), there's no much of a
> point in debating about the best address size, because we are not goin
> to change it.
> --
> Fernando Gont
> SI6 Networks
> e-mail: fgont@si6networks.com
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
>
>
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