From: Jonathan Hui <[email protected]>
Date: Sun, 12 Apr 2009 11:26:19 -0700
On Apr 12, 2009, at 3:42 AM, Zach Shelby wrote:
>> Specific to the 6LoWPAN ND draft, you do bring up an important case
>> - one where two or more Edge Routers are not connected by a
>> "backbone" network. I think there are interesting questions there
>> that are not dealt with in the current 6LoWPAN ND draft (e.g. how
>> is the whiteboard information distributed between edge routers if
>> at all? can we have a particular whiteboard specific for a prefix
>> maintained at only the Edge Router that advertises that prefix? do
>> whiteboards have to be maintained at edge routers?). We should
>> probably open a new thread on this topic in the 6LoWPAN ML...
>
> The Whiteboard is specific to a LoWPAN (= a prefix). Whiteboard
> information is not distributed between different LoWPANs (there is
> no point). In an extended LoWPAN multiple whiteboards on ARs are
> part of the same LoWPAN (same prefix) and use a backbone link to
> perform DAD and claim/defend node addresses across the whole LoWPAN.
Be careful about your definition of a "LoWPAN". Just because a LoWPAN
is defined by a single prefix doesn't mean that a PAN cannot support
multiple prefixes.
In Richard's case, I see two different Access Routers *not* connected
over a backbone but advertise different prefixes to the same PAN.
Nodes in the PAN may be multihomed and configure addresses for the two
different networks. If we define a whiteboard to manage addresses for
a particular prefix, then we have two whiteboards and let's assume
that each resides at their respective advertising Access Router.
Ouch. I have been worrying about where to find the space to
store one whiteboard and now there are two. Does the
whiteboard have to be on a LoWPAN device or can it be on
some other router reachable via a backhaul network?
-Richard Kelsey
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