On Oct 27, 2010, at 14:56, Anders Brandt wrote: > Is the NS+ARO message sent with multicast when I do registration the first > time?
One of the problems with specifying 6LoWPAN-ND as a delta to 4861 is that it more than doubles the effective size of the spec (6LoWPAN-ND is 59 pages, 4861 is 97 pages). 4861 says: 4.3. Neighbor Solicitation Message Format ... Neighbor Solicitations are multicast when the node needs to resolve an address and unicast when the node seeks to verify the reachability of a neighbor. Well, we don't need to resolve an address, so it should be unicast. I think the general rule is: -- Hosts only ever multicast RS (link-local, which is just radio-range for Route-Over!) -- Routers MAY multicast RAs, but generally unicast them -- NS and NA (as well as DAR/DAC) are never multicast. I think it couldn't hurt to say this succinctly somewhere. But the answer to your specific question is in there: 5.1. Forbidden Actions A host would never multicast a Neighbor Solicitation message. 5.2. Interface Initialization ...nobody multicasts Neighbor Solicitations in this type of network See also section 3: The most important part of the optimizations is the evolved host-to- router interaction that allows for sleeping nodes and avoids using multicast Neighbor Discovery messages except for the case of a host finding an initial set of default routers, and redoing such determination when that set of routers have become unreachable. But then there is some weird text in 6.5.5: Optionally Routers can use multicast Neighbor Solicitations as in [RFC4861] to resolve each others link-layer addresses. Thus Routers MAY multicast Neighbor Solicitations for other routers, for example as a result of receiving some routing protocol update. Routers MUST respond to multicast Neighbor Solicitations. This implies that Routers MUST join the Solicited-node multicast addresses as specified in [RFC4861]. Rationale is not given and unknown to me; I don't think one should implement either of these MUSTs. Gruesse, Carsten _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
