Hi Etienne, I’m also not sure many of the classical network operators assembled in NANOG work with 6LoWPANs today, but I still can answer your question.
> While trying to build a holistic view of LoWPANs, I'm consulting the IETF's > informational and standards documents. > > I'm struck by the impression that, despite the significance of RFC6775's > extension of Neighbor Discovery(ND) to low-power and lossy networks (LLNs), > it is largely ignored by RFC6550 (RPL), with little to no reference to the > ontological plane created in RFC6775's terminology section. Yes, you could say that. ND (Neighbor discovery) describes interfaces between hosts and between hosts and routers. 6LoWPAN-ND does not use host-to-host interfaces (different from Ethernet, all traffic goes over routers, which RFC 4861 already forsaw in the L — on-link — bit, which isn’t set in 6LoWPAN-ND). RFC 6550 was completed at a time when many people who came in from the WSN (wireless sensor network) world thought they could get away with a network that is wholly composed of routers. Even the “leaf” nodes in the RPL world were participating in the routing protocol and therefore didn’t really need a host-router interface. There was no separate host-router interface in that world, because there were no non-router hosts. > (a) router advertisements and router solicitations are substituted by DAG > information objects (DIO) and DAG information solicitations (DIS) Right, DIO and DAO are router-to-router messages. If there are no hosts (and routers don’t bootstrap themselves as hosts), you don’t need ND. > (b) the terms "mesh-under" and "route-over" (widely cited), defined in > RFC6775, are absent from RFC6550 RFC6550 is route over by definition. Actually, the term was coined by the people working closely with the RPL development; RFC 6775 does appropriate it as 6LoWPAN-ND is applicable in either case. > (c) jarringly: RFC6775 describes the route-over topologies as multi-IP-hop, > while RFC6550 gathers DODAG nodes within the confines of the same IPv6 prefix > as their border router - no multiple IP hops. I’m not sure where you get this interpretation: RFC 6550 (RPL) is very much about IP hops. Maybe you mean the address architecture that was defined explicitly in RFC 6775; RFC 6550 does not really say much about addresses. Note that the RPL people have since proceeded to (at least partially) embrace the host-router concept from the IP architecture; RFC 8505 is an update to RFC 6775 that makes 6LoWPAN-ND more palatable to RPL people. I have CCed Pascal Thubert who, as a co-author to all three RFCs, certainly will have another perspective on this. Grüße, Carsten
