Responses - well, mostly more questions - inline...
On Nov 16, 2009, at 1:05 AM 11/16/09, Carsten Bormann wrote:
Quick answers:
On Nov 16, 2009, at 06:43, Ralph Droms wrote:
1. In a mesh-under network, the L2 characteristics of the lowpan are
close to those usually assumed for implementation of IPv6; in
particular, there are no "lowpan routers" at L3 and L3 messages *can*
be delivered (perhaps with lower probability of success) directly
between lowpan nodes. Why is ND not sufficient in this model?
RFC 4861 ND works in a pure RFC 4944 mesh-under network if:
1) the mesh-under (L2) routing protocol provides subnet-wide
multicast,
2) that is efficient enough to be used for routine ND messages,
3) nodes are awake often enough to detect and reply to NS messages.
Such networks do exist, but these assumptions are not necessarily
compatible with many application scenarios we have in mind; this is
the reason we started with ND optimizations.
OK, and I understand you're working on application scenarios. I think
you need a digest from the applications scenarios into a set of
characteristics of the underlying L2 services that is explicitly
written down somewhere.
Can you reuse the scenario work from the roll WG?
Would
proxy ND be sufficient?
I haven't seen such a design yet, so I don't know.
Might be good to consider it...
2. In a route-over network, all nodes are routers
That is not the assumption: The assumption is that there are hosts
and routers, and that the forwarding function is performed by the
routers. There needs to be a protocol that enables hosts to
register themselves to routers, independent of the routing protocol.
Is it commonly assumed in lowpans that there are both hosts and
routers or is that architectural assumption specific to the 6lowpan/
802.15.4 work?
Since the host-router relationship is somewhat ephemeral due to the
nature of the wireless links, address assignment needs to be lowpan-
wide instead of per host-router relationship.
As ND-07 is not by itself supporting host-host communication,
address resolution only happens between hosts and routers.
Do you mean that the only address resolution is for a router to
resolve the MAC address of a destination host?
Re one other term: "relaying" is the term ND-07 is using for what
routers do between themselves to process host NR messages; it is not
IP forwarding.
Is this relaying specific to ND-07; i.e., does ND-07 require a
forwarding overlay?
It is probably more appropriate to give the inter-router message a
different name (e.g., relayed NR, RNR), so the confusion between
this relaying process and IP forwarding is reduced; this is the part
that will move to the second document after the split.
Gruesse, Carsten
- Ralph
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