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). >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@xxxxxxxxxxxxxxx PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
