rfc4944 doesn't seem to say a link-local scope multicast address is
mapped into 0xffff, but probably into something like 0x8001.
That depends.
Section 9 addressing is explicitly for mesh-under only (section 9,
first sentence) -- if there is an actual multicast framework under/in
the adaptation layer, it was considered useful to map the L3 multicast
addresses to different MAC addresses as well.
If not, all multicast maps to 0xffff broadcast.
BEsides, it doesn't seem to say what IP address corresponds to the
16bit MAC broadcast address 0xffff. If the rule used for mapping
ff02::1 into 0x8001 were used to map 0xffff into an IP address then
that would be ff02::9f, which is different than the all-nodes link-
scoped multicast address ff02::1.
No, section 9 addressing only uses 16-bit addresses of the form
100xxxxx xxxxxxxx.
0xffff is 11111111 11111111, so it is not section 9 addressing.
For example NS is sent to 33:33::1/ff02::1
whereas RS is sent to 33:33::2/ff02::2
We don't use Ethernet's 48-bit MAC addresses in 4944.
(Let's try to focus the discussion on the 6lowpan list to 6lowpan,
please.)
PS: there is more error in rfc4944 saying that "IPv6 level multicast
packets MUST be carried as link layer broadcast frames" - because
only the link-local scoped IP multicast packets should, and not the
globally-scoped multicast packets.
This is the non-mesh-under multicast case. No error.
PPS: there is even more error in rfc4944 requiring every byte in the
IP multicast address (bytes 1 to 16) to correspond to "100 DST[15]
DST[16]" because globally multicast packets (i.e. group ff0e::1) I
doubt should be multicast at link-layer, they should be unicasted to
the router.
Not with mesh-under multicast.
Discussing mesh-under multicast is always a bit difficult because
there is no actual system instance to discuss it relative to.
One could argue that putting currently unused functionality into 4944
might have been premature, but it might also help commonality of any
mesh-under multicast solutions that arise.
Gruesse, Carsten
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