Eric, > -----Original Message----- > From: Fleischman, Eric > Sent: Wednesday, July 07, 2010 11:20 AM > To: Templin, Fred L; Robin Whittle; RRG > Subject: RE: [rrg] ILNPv6 Mobility problem > > > Back when we had a huge bridging network, we had multiple instances of > MAC-address collisions in our > network. This was one of the reasons why DECnet Phase IV reassigned all MAC > addresses (i.e., to > ensure that MAC addresses were indeed unique within the DECnet network). > > It is possible that this issue is no longer a problem -- I just don't know. > However, the gray-hairs > among us remember the time when vendor-assigned MAC address uniqueness was a > theoretical claim that > far-too-often wasn't true in real-life.
I think we agree. As an optimist, I wish it weren't so but wishing doesn't make it a reality. Possibilities for colliding MAC addresses is exactly why IPv6 links are required to run duplicate address detection, which is another matter for enormous debate in MANET Autoconf (see also "optimistic DAD" RFC4429). If you think about the process of assigning managed MAC addresses, there are multiple levels of trust that are stacked like a house of cards. To assume MAC uniqueness, one would have to trust all vendors - great and small - to not make any mistakes in avoiding duplicates. Plus, each vendor only gets to number its MAC addresses out of 2^24 possibilities for each of its vendor codes, so probabilistic uniqueness is not viable. Plus, think about all of the 3+yr old networking hardware that has been thrown away in dumps and long forgotten. Each one of those junked NICs takes with it a MAC address that can never be reassigned... Fred [email protected] > > -----Original Message----- > From Fred Templin > > From: [email protected] [mailto:[email protected]] On Behalf Of > > Robin Whittle > > > > > I read all the material of all the proposals, including ILNP, and > > commented on them all on the list. I haven't read the very latest > > versions of the proposals. My critiques of ILNP and other such Loc/ID > > Separation (Core-Edge Elimination) architectures are well known: > > > > http://www.ietf.org/mail-archive/web/rrg/current/msg06219.html > > > > and are not solvable by the small details which change from one > > version of a draft to another. So forgive me if I haven't read all of > > Ran's latest versions end-to-end. > > > > > > > As has been documented for years, and has been patiently explained > > > many times on this list, it is recommended to synthesize a > > > global-scope > > > EUI-64 ID from one of a host's globally unique hardware IDs, such as > > > an Ethernet MAC address. > > > > Sure - but that doesn't eliminate the possibility of clashes. > > > > There could be two Ethernet interfaces with the same MAC - and there > > will be many devices which have no Ethernet interface or other > > component with a MAC. > > The MANET Autoconf community has debated for years about the guaranteed > uniqueness of MAC addresses > without conclusion. > The frequently heard argument is that MAC addresses are configured by > vendors, and anything that can > be configured can be misconfigured. > > Being an optimist, I am actually a believer in the assumed uniqueness of MAC > addresses. But, there > are many pessimists in the MANET Autoconf world and I'm sure elsewhere as > well. > > Fred > [email protected] > _______________________________________________ rrg mailing list [email protected] http://www.irtf.org/mailman/listinfo/rrg
