Zach Shelby a écrit :
[...]
If you try to do a multicast with scope > 2, then you have a flooding
problem unless multicast is implemented in some other way. This is
why we use the Whiteboard approach in 6lowpan-nd, to avoid the need
to flood the LoWPAN.
6lowpan-ND Whiteboard instead of link-layer multicast... maybe we
should make another thread...
For example it says:
Another consequence [of forming address from MAC] is that the
link-local address is presumably unique on the Extended LoWPAN,
This is not a very safe assumption IMHO.
At least because the uniqueness assumed with IPv6 addresses formed from
short 16bit addresses is a uniqueness relative to a "PAN id" (and not to
a LoWPAN, not an Extended LoWPAN), even less globally unique. And we
don't know anything about the uniqueness of PAN-IDs, do we?
which enables the use of Optimistic Duplicate Address Detection
(oDAD) [RFC4429] over the Transit Link and the LoWPAN.
AFAIK oDAD does use the typical ND link-local multicast messages, so
does 6LoWPAN use ND link-local multicast messages or not?
(Transit Link on Edge Router overlaps its link-local scope over the
LoWPAN)
To simplify address resolution it is assumed that nodes within a
LoWPAN use addresses in a homogeneous way and that the unicast IPv6
address IIDs resolve directly to a corresponding link-layer address.
I just suppose it unsafe to assume an IPv6 address IIDs address resolves
directly into a MAC address, IMHO. Because:
-it prohibits the use of manually assigned link-local addresses.
-it requires link-layers to have MAC addresses (not all have).
-in particular for IPv6-over-802.15.4 it is difficult to
distinguish an IID to correspond to a short (16bit) or normal MAC
address. What is the MAC address from which this IPv6 address was
formed?
fe80::21:70ff:feb8:8252
After removing the fffe and the fe80 - is there a short 16bit MAC
address in there concatenated to the PAN ID? Or is it a locally unique
manually assigned 48bit MAC address? Or a locally-unique self-derived
non-standard USB address?
Upon a registration flow, an edge router doing DAD
Doing DAD or DAD?
If successful, this address is returned in an Address Option of the
RC with the 'A' flag set and the assigned IPv6 address formed from
the generated link-layer address with the defualt prefix inline.
This is typically a DHCPv6 function (a router forming an address for a
host and sending it for assignment on interface). One would expect the
draft to refer DHCPv6 and say why not, no?
Alex
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