MAC addresses are on a shared medium. ULA are disjoint. The risk is that 1 in 220 networks in a field of 100,000 things pick the same value of NON ROUTABLE and then.. decide to join. Now, tell me the risk of 1 in 220 things, both picking the same ULA, *AND* seeking to join their private networks. -G On Thu, Jan 21, 2021 at 11:39 AM Christopher Morrow <morrowc.lists@xxxxxxxxx> wrote: > > (I'm not a ULA fan, it's going to cause problems.. but) > > On Wed, Jan 20, 2021 at 7:16 PM John R Levine <johnl@xxxxxxxxx> wrote: > > > > > No. Collissions are actually almost guaranteed (birthday paradox). > > > > When I do the birthday paradox calculation, I find that the chances that > > 100,000 random numbers each 40 bits long are all different is about 95%. > > I'll take those odds. > > > > Warren made this website/application/etc: > http://mac-collision-probability.appspot.com/calculate > > which was used for privacy address problems/discussions, but... if you > make it 40 bits and 100,000 stations > apparently you'll get a collision 1 out of 220 times. I think that > means that ULA network selections COULD overlap at about the same > rate. > > There are ~1.4m small businesses in the US, if they all chose ULA > that's more than a few collisions. > Collisions matter because when 2 networks that collide come together > it's messy :( to untangle and decide whom is going to do what :( > it's also not always obvious that it's happening :( until something crashes :( > > Regards, > > John Levine, johnl@xxxxxxxxx, Taughannock Networks, Trumansburg NY > > Please consider the environment before reading this e-mail. https://jl.ly > > >
