In message <17786.1318379...@marajade.sandelman.ca> Michael Richardson writes: > >>>>> "Russ" =3D=3D Russ White <ru...@riw.us> writes: > Russ> You need a unique identifier at the equipment level for > Russ> anything you intend to auto-configure --autoconfiguring > Russ> uniqueness is a very hard, probably impossible, problem on a > Russ> global scale. So we need to count on this one thing, no matter > Russ> what else we might need to back in to. > > Russ> Now, it might be possible to some hash over a GPS location for > Russ> a "base," and then add on MAC addresses, or some such, but > > We've assumed a unique MAC, which is 48 bits long.=20 > But OSPF router-id is 32 bits. What is the likelyhood of a collision=20 > in the bottom 32-bits of the MAC?=20
Each organization has one or more unique OUI which includes one of the bottom four bytes. The next three (of those four) are unique only within the OUI which is the top three bytes (but with two bits given special meaning). So what are the chances that two organization start numbering the bottom bits at zero and work their way up until the bottom three bits are filled. Since there are way more than 256 organizations that have an OUI, collisions, while rare, can happen. If there is a way to recover from a collision, then its a complete non-issue and a random number can be used. Curtis _______________________________________________ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
