Hi Zach: > > > Hi Pascal, > > > > I fully agree with you. > > In my opinion anything spanning multiple IP hops should not be done by > ND. > > That logic doesn't work anymore with route-over LoWPANs. As the prefixes > are spanning the whole LoWPAN there is a natural need for ND to help with > that. In the case of RPL, the WG may decide to disseminate some things such > as prefix information between routers in a LoWPAN using the routing > protocol. 6lowpan-nd-09 states clearly that you may do that, so nothing > stopping RPL there. What is this argument about? You are complaining about > something that is not a problem? > > Now RPL isn't the only routing protocol.... 6lowpan-nd-09 provides an > optional mechanism of using RS/RA for disseminating prefix and context > information between all routers in a LoWPAN that is routing protocol > independent. Regardless of RPL, this will surely come in handy and some > routing protocols may even specify to use this mechanism.
[Pascal] Dissemination is the easy piece in the routing protocol. The hard piece is maintenance. If you try to maintain the connectivity within the subnet, you end up building an SGP like RPL. Do you really want to rediscover what we've been through? > Let me remind you of how RPL started by the way. In the beginning the idea > was to piggyback RPL information on ND traffic as there were already similar > flows. Eventually the WG decided to give RPL its own messages instead of > piggybacking as ND options. Now it has gone to the extreme of RPL being the [Pascal] Both the ROLL fundamentals and the backbone router drafts extended ND. ROLL Fundamentals inherited from the NINA model that was a recursive host to router model (NINA meant Network In Node). The goal was to have a consistent host to router interface all the way up the DAG. We split the work between 2 stove pipes and that spirit was lost. > one and only protocol and everything must be carried on that.... Quite a > change! Next we could piggyback DHCPv6 on RPL, use RPL for DAD, and what > the heck, let's go for DNS too... Starts to sound like a shopping-TV ad for a > super-vegetable-processing-miracle doesn't it? [Pascal] This is the direct consequence of keeping 6LoWPAN and RPL apart. None can refer to / depend on the other. On the ROLL side: RPL needs all nodes to be routers so it can claim it does not need ND. Truth is, a RPL node still requires ND for address allocation. On the 6LoWPAN side: ND is partial solution with no applicability in the real world. Truth is, 6LoWPAN ND needs RPL for tying the subnet together. > > > > On a related topic.... > > 6lowpan network have the particularity that you cannot use on-link > > prefix due to the non-transitivity of the wireless links. This means > > we need to tell routers how to reach neighboring IPv6 hosts. So > > essentially 6lowpan-ND is using a registration mechanism to establish > > a "route" between the router and the host. > > It is actually letting the host and router know about each other (router > discovery), their reachability (NUD) and their L2 addresses (address > resolution). These are all standard features of ND. > > > It is not clear to me whether this is the role of ND or of the routing > > protocol. I think it could actually be both. > > Hence the questions: > > - Are IPv6 hosts possible in a 6lowpan network where the RPL protocol > > is used? > > Better be, or you just broke an important model of IPv6. I would say it MUST > be possible for hosts to attach to a LoWPAN running RPL (and stay blissfully > ignorant of RPL). [Pascal]. If you look at it, the IP header is the abstraction of a set of instructions by the end point to the routing fabric. The flow label is an integral part of that abstraction and RPL makes use of it to select an instance. This capability is much needed in a LLN a host connected to a RPL network should be able to make use of it. A given deployment can always resort to instance 0 to accept nodes that are not RPL aware at all.. > > - Should IPv6 hosts be part of a RPL topology (as leaf node) or should > > IPv6 hosts use the 6lowpan-ND host-router spec? > > ND is clearly the standard host-router interface regardless of IPv6 or > 6LoWPAN. Forcing hosts to know anything about RPL would be insane... [Pascal] Just as incorporating a routing protocol in ND would be. 6LoWPAN managed to work with ISA100. ROLL managed to work with ZigBee IP. Can't 6LoWPAN and ROLL manage to work together now? Pascal _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
