On Oct 14, 2009, at 1:27 , Colin O'Flynn wrote:
Hi Jonathan,
I agree with you there - these nodes would *not* be participating in
real IP
or mesh forwarding.
Right, not all nodes are routers. We do have the concept of a host,
and it is a useful one also in LoWPANs.
However the ND process needs to function with these nodes. If we
rely on
4861, these nodes which are going to miss packets must have a way to
defend
their address!
Jonathan is assuming the link provides a service guaranteeing nodes
within radio range can communicate within some bounded latency using
duty-cycling or other techniques. This is an assumption you may be
able to make. But if you do that then routers may need to answer on
behalf of hosts as those hosts may be sleeping asynchronously to
eachother if the router is e.g. powered.
It is safe to assume that there is synchronization on the host-router
and router-router interfaces - OK. It is not safe to assume
synchronization between peer hosts attached to the same router. Nor
between different sections of a LoWPAN. No, we are not trying to solve
DTN.
Zach
-Colin
-----Original Message-----
From: Jonathan Hui [mailto:[email protected]]
Sent: October 13, 2009 11:04 PM
To: Colin O'Flynn
Cc: 'Adam Dunkels'; '6lowpan'
Subject: Re: [6lowpan] Fundamental concerns about 6lowpan ND
Hi Colin,
On Oct 13, 2009, at 2:56 PM, Colin O'Flynn wrote:
My concern for this sleeping method is very low power nodes. These
would be
parasitic nodes for example that can only wake up every few seconds
at most.
These super-low power nodes could not listen continuously. Forcing
them to
require waking up would basically eliminate them from the picture.
For these very special devices, I often prefer to view them as
wireless peripherals rather than IP devices. They most likely won't
be able to participate in forwarding/routing functions. Any bi-
directional communication tends not to be end-to-end since they want
to minimize round-trip time.
--
Jonathan Hui
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Head of Research
Sensinode Ltd.
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