On 05/10/10 05:41 AM, Pascal Thubert (pthubert) wrote:
Hi Erik:
I think Zach and I came up with a common understanding. My concern had
not to do with a backbone. It has to do with 2 routers in a same mesh
under topology, and without the assumption that any node can reach any
other node using the mesh under technology.
To illustrate this, say you use the ND base draft in a Frame Relay
network. You build a hub and spoke with the router at the hub. The
router is at a central office, and there are DTEs at the branch office.
I agree, the draft works great! The router can resolve any incoming
packet because it has a proactive registration for it. Then we want to
place a second router.
OK
We place a switch between those and we split the
DLCIs in half between the routers. So each of the routers get half of
the registrations. There is simply no DLCI for the hosts to register to
the other router.
But that isn't how nd-09 works. See section 5.5.
(The hosts register with more than one default router.)
In a same fashion, you do not want a node to register to all routers and
receive multicast from all routers in a LoWPAN that grows to the
thousands.
If applications want to do multicast in a lowpan then the hosts would
use MLD. That is orthogonal to the nd-09 registration option.
So with the draft alone, if router 1 gets a packet for a node attached
to router B, the registration does not help. So the router will either
multicast, which we wanted to avoid, or drop. That's my concern, that's
why I've been telling you it was broken for mesh under. Zach and I
agreed we could resolve this question by saying that 2 routers is
already an extended LoWPAN, that will be addressed by the spec left to
be done. Would you agree with that resolution?
Might make sense for you to read nd-09, since it doesn't work that way.
Erik
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