Hi,
Thread now on 6lowpan only.
Jonathan Hui wrote:
Hi Richard,
If both egress routers are advertising default routes, then I see no
problem with the stub network deciding which to choose. If they have
different costs, then definitely the two should be advertising different
costs. If the meter network only wants to accept traffic to a particular
prefix, then it should only be advertising that.
Agreed.
I do think we need to better define what exactly is an Edge Router in
and out of a 6lowpan context. In general, I think of an Edge Router as
nothing more than a router that routes between an L2N network to a
non-L2N network. In the 6lowpan context, we typically associate an Edge
Router with one that also maintains the "whiteboard" for nodes in the
6lowpan network. However, I'm not sure we need to bind them together.
Yep, I agree it needs to be a generic term usable in both 6LoWPAN and IP
contexts (e.g. in roll).
Proposal 1: We call it an Access Router (AR) and agree to share that
term with ROLL. An AR is simply a router that routes between L2N and
non-L2N networks.
Proposal 2: We define Whiteboard as an additional feature that SHOULD be
implemented in an Access Router but MAY be implemented on any other node
in the network (e.g. in the ad-hoc LoWPAN case).
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.
A Whiteboard does not need to be located at an AR, but it is a logical
place in most cases. In the Extended LoWPAN case the whiteboard needs to
be located on nodes which have a shared backbone link (usually ARs).
We discuss that a little in the ND draft but I think it can be expanded
to make that clear with an example.
- Zach
--
Jonathan Hui
On Apr 10, 2009, at 1:01 PM, Richard Kelsey wrote:
From: Carsten Bormann <[email protected]>
Date: Fri, 10 Apr 2009 19:00:42 +0200
(I don't tend to think about the case where there is no
Edge Router -- ...)
I have a question on this, stemming from my lack of
familiarity with the details of IP routing.
Suppose I have a 6LowPAN/ROLL network being used for energy
management in a home. The network includes the electric
meter, which has a backhaul connection back to the utility.
The utility, being very protective of its backhaul network,
has a firewall in the meter to keep out everything except
the utility's own traffic. Given the presence of the
firewall, does it still make sense to use the meter as an
Edge Router?
-Richard Kelsey
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Zach Shelby
Head of Research
Sensinode Ltd.
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88610 Vuokatti, FINLAND
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