If an LV never ever wanted to get a PD from anything other than an IV, and an IV could only ever expect to delegate to a LV, then I see no problem. On the other hand, if these things do expect the same physical links to be used to connect with other ecosystems (like home networks or hotspots) that will be well-established in the IPv6 world by the time these vehicles come along, then I think this proposal has some undesirable ramifications.
Questions: Would an LV ever expect to use the same physical link to connect to a home network or hotspot, instead of an IV? Would an IV ever expect to provide connectivity for devices that think they're inside a home network (e.g., maybe they're in a RV park, and the RV-owners networks are made up of traditional home networking components, so they can connect to non-cellular uplinks when such are available; maybe the IV is the truck pulling a trailer, and there's a regular home network set up in the trailer). If the answer is no, then read no further. If the answer is yes, then I'd like to dive a little deeper into understanding the ramifications of what is proposed. Hotspots and CE (home network) routers will use IA_PD for prefix delegation. Sub-delegating routers attaching to them will request prefixes by IA_PD. Which means either the LV would have to support both ND_PD and IA_PD, or the hotspot/CE router would have to do so. And whoever does both would have to know which to use in which case, and make sure they don't get things confused between the two. Somebody's complexity-of-code has just been doubled (or more) by the addition of a 2nd way to do the same thing. If it's the hotspot/CE router, then it would have to run both delegation mechanisms simultaneously and keep track of prefixes delegated by IA_PD and ND_PD -- making sure there's no overlap in delegated prefixes and such. On the IV side -- if the IV expects to be able to provide connectivity to regular CE routers as well as LVs, then either all of the CE routers would have to support both requesting mechanisms, or the IV would have to support both delegating mechanisms (simultaneously, in case some attaching devices are LV and some are regular CE routers). It would be interesting to see who ended up having to do both mechanisms: vehicles or everyone else. My preference would be that vehicles should be the ones to incur the additional complexity, since they're the ones who caused the additional complexity. Of course, we don't get to choose -- the marketplace chooses. Generally, the choice is made according to (1) who sees greater benefit in being able to connect to the other, and (2) who was there first and already has a significant embedded base. My tea leaf reading is that there's going to be a huge embedded base of IPv6-connected hotspots and CE routers with IA_PD long before these vehicles come to fruition. Home networks and hotspots are already successful without connecting to vehicles. For "connected vehicles" to be desirable in the eyes of consumers, I believe they will have to be able to connect to the consumers' home networks. So I think vehicles will have to be the ones to go the extra mile to connect to existing ecosy stems. My Conclusion: If vehicles are really only ever expected to talk to other vehicles via this particular link, the proposal could be considered in the vacuum of its stand-alone ecosystem. But if the possibility is likely that vehicles will want to interact with other ecosystems over that same link, then somebody has to suffer and support both ways of doing the same thing. The savings of a couple of short messages at attachment time is, IMO, not worth the additional complexity on either side. And the advantage to vehicles of being able to operate in both ecosystems is much greater than the advantage of saving a couple of messages at attachment time. Barbara -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
