Hi Brian,
----- Original Message ----- > From: Brian E Carpenter <[email protected]> > To: Mark ZZZ Smith <[email protected]> > Cc: IPv6 IPv6 List <[email protected]> > Sent: Tuesday, 23 July 2013 8:00 AM > Subject: Re: 6MAN WG Last Call: <draft-ietf-6man-ug-01.txt> > > On 23/07/2013 09:12, Mark ZZZ Smith wrote: >> Hi, >> <snip> >> >> " Also, there is >> evidence from the field that IEEE MAC addresses with "u" = 0 > are >> sometime incorrectly assigned to multiple MAC interfaces. Firstly, >> there are recurrent reports of manufacturers assigning the same MAC >> address to multiple devices. Secondly, significant re-use of the >> same virtual MAC address is reported in virtual machine environments. > " >> >> I found this text a bit confusing. The '"u" = 0' term > read like it was referring to locally unique IEEE MAC addresses ("unique > equals no"), and then the 2nd sentence is referring to globally unique (but > duplicated and therefore not actually globally unique) MAC addresses, u = 1 > in > an IPv6 IID, the opposite of what the previous sentence was referring to. > Then > the third sentence seems to be describing to what the first sentence was > referring to. I think the cause of the confusion might be that IEEE use the > "locally assigned" bit to distinguish locally generated or not (i.e., > "l" = 0 for globally unique), where as IPv6 IIDs have renamed it to > "u" bit when the value is inverted. I'd suggest trying to ensure > the IEEE terminology is used when IEEE addresses are discussed to make it > clearer what the properties of the IEEE address are. > > Yep. I remember complaining when the bit inversion was first proposed > that it would lead to years of confusion. Which IEEE standard is the > basic reference for their terminology? > I understand the canonical definition of 48-bit universal LAN MAC addresses is in: IEEE Std 802®-2001 - 802® IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture (http://standards.ieee.org/getieee802/download/802-2001.pdf) >From page 21, it seems what I knew as the "locally assigned" bit is actually >the "Universally or Locally administered (U/L) address bit". Regards, Mark. -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
