In particular, I think that it would be
unfortunate if forwarding messages between two LoWPANs
required that any router doing such forwarding have a
whiteboard. Is this the case?
Right now, the architecture is that packets only enter and leave a
LoWPAN through an ER.
ERs have whiteboards and (if multiple) are interconnected by a fast
backbone link.
Can you give more details of a scenario where this is suboptimal?
Would it be possible to avoid the need for a whiteboard in a
network by only using IPv6 addresses derived from EUI64s?
While conflicts are still possible, they are very unlikely
(outside of development and testing, where they can happen
with some regularity).
I've got one word for you: counterfeiting.
(So the point is less the detection of IPv6 address collisions but of
EUI-64 collisions, indeed.)
802.15.4 16-bit addresses could
still be used for link-layer next-hop addresses, as that
requires only local, and not global, conflict detection.
How does local conflict detection work when nodes tend to attach to
routers they haven't seen before?
Of course, a node could have many 16-bit short addresses if we were
using the cluster approach (with separate PAN IDs per router).
Is that what you are hinting at?
(Such an approach would cost some header compression efficiency, at
about 8 bytes per message.)
On a related note, there is some discussion of what happens
when a non-Edge-Router reboots (using a lollipop mechanism
for TIDs), but I didn't see anything about what happens if
an Edge Router reboots. Is the expectation that the
whiteboard will be kept in non-volatile storage?
That would help.
(If you don't do that, it will be hard to avoid a blackout for about a
registration lifetime, unless we have something like an "ER reboot
sequence" disseminated through the network. Which will bring a
galopping herd of re-registrations, unless dithered, which will cause
blackouts for the dithering period.)
Gruesse, Carsten
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