> From: ipv6-boun...@ietf.org [mailto:ipv6-boun...@ietf.org] On Behalf Of > Alexandru Petrescu
> Yes, the ULA prefix (RFC 4193 section 3.2.2) generates a 48bit prefix > randomly. That suggested algorithm is seeded by time, EUI-64 into a > key, and then SHA-1. > > > Anyway.. the idea is that you randomize the prefix... > > Yes. We may need to say how. > > Just saying RNG may not be enough, I dont know. I really don't put much weight on this. It's just one suggestion. I dare say, pick a decent PRNG, pick a seed out of the air, and for all intents and purposes, you have your ULA prefix. After all, this use of ULA is only for in-vehicle comms, and should not transit through any car-Internet router. Randomness is only a safety net, in case a ULA sneaks out of the local router. I don't think we should tie the VIN or any EUI-64 strictly to this idea of using ULAs. > Also, that Network mobility doesnt prohibit neither suggests that the > prefix of a moving network (MNP: Mobile Network Prefix) be exchanged > between two distinct moving networks such as to establish routes > between > them (route exchange). Well, I have a question about this. I've seen mobility done in a number of ways. Move individual interfaces, using the home agent approach; move entire address blocks, where the routing protocol keeps track of subnet location; or use a link layer that always ties the moving subnet(s) to the same geographic location "back home," making the job easier for the IP layer. Added to this, for a vehicle scenario, we may (probably will) also need something along the lines of 802.11 ad-hoc networks, for those tactical car-car and car-road comms. In principle, can't a combination of all of these schemes be used in vehicles? For instance, if your IP service is the type that replaces the OnStar scheme (used by GM in the US), a lot of that information is not overly time constrained. And since OnStar is a 3G system, it "knows" what each client's home network is. > The random part of the ULA may be needed for inter-vehicle > communications. I.e. use fd00:fef2:3214::/64 inside one vehicle, > and fd00:fff2:3214::/64 in the other vehicle. Use no prefix on the > ad-hoc link between the two egress interfaces of the mobile router (use > their link-local addresses there). > > If those two prefixes were not random, then collision between prefixes > may occur the moment the routes are exchanged between the vehicles. No, I would not contaminate the Internet deliberately this way. It seems to me that each car should be assigned a /64 prefix which is globally unique, for this sort of use. Just like every household. I really don't see why this type of inter-car communications should be thought of as any different from home nets. And again, the mobility aspect can be resolved in at least two different ways that I believe to be in common use already. Bert -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
