Re: [ieee-ietf-coord] Rationale for 0xFFFE as octets 4 and 5 pf EUI-64?
Charlie Perkins <charles.perkins@earthlink.net> Mon, 25 June 2018 17:46 UTC
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To: Donald Eastlake <d3e3e3@gmail.com>, Geoff Thompson <thompson@ieee.org>
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From: Charlie Perkins <charles.perkins@earthlink.net>
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Date: Mon, 25 Jun 2018 10:46:04 -0700
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Subject: Re: [ieee-ietf-coord] Rationale for 0xFFFE as octets 4 and 5 pf EUI-64?
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Hello folks, The reason why I asked about why 0xFFFE was chosen, was because I am trying to understand how best to do something similar for 802.15 devices that have a PAN-ID and a 16-bit short address as in IEEE 1901.2. Or, if someone has already done it, then even better. What I saw was to make the PAN-ID into the leading 16 bits, by analogy to making the OUI into the leading 24 bits. But the OUI already had bits set aside for U/L and I/G, whereas the PAN ID does not. So, setting the U/L bit would effectively change the PAN-ID and that seems wrong to me. A similar problem exists already in IEEE 1901.1 because the NID (Network ID) is made into the leading 24 bits of the EUI-64. So, two devices on different Networks that happen to have the same 16-bit equipment identifier could end up with the same IPv6 address. I have looked in a number of places for an existing design, or for information to guide the design, so far coming up empty handed. Thanks for any help! Regards, Charlie P. On 6/24/2018 9:22 PM, Donald Eastlake wrote: > OK, it would have been better if I had said "converts the format of X > to Y" instead of "converts X to Y". > > In any case, the original question from Charlie had nothing to do with > why or how a larger 64 bit MAC address space would be of benefit or > what its goals were. I believe he was just asking where the 0xFFFE > came from that is actually and currently used in, for example, > construction of some IPv6 addresses from 48 bit MAC addresses. As far > as I know it came from the IEEE. See for example > http://standards.ieee.org/develop/regauth/tut/eui.pdf which, while it > deprecates this "mapping", still documents FF-FF and FF-FE as > insertions. An earlier IEEE tutorial which, as I call, documented this > mapping without any deprecation, seems to no longer be on the web. > > Thanks, > Donald > =============================== > Donald E. Eastlake 3rd +1-508-333-2270 (cell) > 155 Beaver Street, Milford, MA 01757 USA > d3e3e3@gmail.com > > > On Sun, Jun 24, 2018 at 9:27 PM, Geoff Thompson <thompson@ieee.org> wrote: >> Inserting "0xFFFF to convert a MAC-48 to and EUI-64" or "0xFFFE to convert >> an EUI-48 to an EUI-64" >> does not actually "convert" anything in a useful way except to to make a >> "EUI-48" readable in a 64 bit system. >> >> The purpose of developing EUI-64 was to have a larger address space that >> could be used for (among other things) software instances. >> Having a fixed 16 bit value in a 64 bit address does nothing towards >> achieving that goal or slowing down the usage of 48 bit addresses to extend >> the life of 802 physical networks. >> >> Geoff Thompson >> >> >> On Jun 24, 2018, at 5:52 PMPDT, Donald Eastlake <d3e3e3@gmail.com> wrote: >> >> Hi Charlie, >> >> As I recall, there is/was this distinction between MAC-48 and EUI-48 >> addresses. I think MAC-48 was just for hardware and EUI-48 was for other >> devices and software. Anyway, you inserted 0xFFFF to convert a MAC-48 to and >> EUI-64 and 0xFFFE to convert an EUI-48 to an EUI-64. The RFCs that talk >> about extending a 48 bit address to 64 bits to use as the low order bits of >> an IPv6 address say that 0xFFFE was used by mistake and that 0xFFFF should >> have been used (see for example the Note on page 22 of RFC 4291) but it was >> decided to stick with 0xFFFE for that purpose. Hope this helps. >> >> Thanks, >> Donald >> =============================== >> Donald E. Eastlake 3rd +1-508-333-2270 (cell) >> 155 Beaver Street, Milford, MA 01757 USA >> d3e3e3@gmail.com >> >> On Fri, Jun 22, 2018 at 9:54 PM, Charlie Perkins >> <charles.perkins@earthlink.net> wrote: >>> Hello folks, >>> >>> Does anyone here remember why 0xFFFE were chosen to be the filler bits >>> (i.e., bytes 4 and 5 of 8) when expanding a 48-bit MAC address to be EUI-64? >>> It is not explained in RFC 2464. >>> >>> Or maybe there was not a reason...? >>> >>> Thanks in advance, >>> Charlie P. >>> >>> _______________________________________________ >>> ieee-ietf-coord mailing list >>> ieee-ietf-coord@ietf.org >>> https://www.ietf.org/mailman/listinfo/ieee-ietf-coord >> >> _______________________________________________ >> ieee-ietf-coord mailing list >> ieee-ietf-coord@ietf.org >> https://www.ietf.org/mailman/listinfo/ieee-ietf-coord >> >> > _______________________________________________ > ieee-ietf-coord mailing list > ieee-ietf-coord@ietf.org > https://www.ietf.org/mailman/listinfo/ieee-ietf-coord >
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Pascal Thubert (pthubert)
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Robert Grow
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Roger Marks
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Pascal Thubert (pthubert)
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Robert Grow
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Pascal Thubert (pthubert)
- Re: [ieee-ietf-coord] Doodle poll to schedule Lat… Stanley, Dorothy
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Robert Grow
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Russ Housley
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… ROBERT GROW
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… ROBERT GROW
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Charlie Perkins
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Pascal Thubert (pthubert)
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Charlie Perkins
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Donald Eastlake
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Donald Eastlake
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… John Messenger
- [ieee-ietf-coord] Rationale for 0xFFFE as octets … Charlie Perkins
- [ieee-ietf-coord] Doodle poll to schedule Late Ju… Stanley, Dorothy
- Re: [ieee-ietf-coord] Rationale for 0xFFFE as oct… Geoff Thompson
- [ieee-ietf-coord] Whether or not RFC 4944 can pro… Charlie Perkins
- Re: [ieee-ietf-coord] Whether or not RFC 4944 can… Pascal Thubert (pthubert)
- Re: [ieee-ietf-coord] Whether or not RFC 4944 can… Charlie Perkins