On Nov 10, 2009, at 7:12 AM, Kris Pister wrote:
> Abandoning the installed base just goes to reinforce the idea
> that IP isn't an appropriate technology for things.
Michael - I think that we have the same goal, but I disagree with
that statement. I think that re-writing every protocol from
discovery through transport to applications, from scratch, is what
reinforces the idea that IP isn't an appropriate technology for
things.
I strongly second this statement. What worries me here is the tendency
to jump on new protocols without any evidence that existing protocols
can be used. Yes there are areas where we need new IP protocols for
constrained devices but there are also many more cases where existing
protocols could be re-used as such or with a small adaptation.
I realize that there are pressures from an installed base, but at
this point it's a tiny fraction of the overall potential. If we let
the 1% installed base dictate the path for the next 99%, we should
do our best to ensure that it's the right path.
ksjp
Stuber, Michael wrote:
Life may be getting better, but that doesn't mean we have the wrong
target. Abandoning the installed base just goes to reinforce the
idea
that IP isn't an appropriate technology for things. Qualifications
for
parts in appliances, meters, and cars may take much longer than in
other
consumer electronics. There are lots of products shipping today with
802.15.4 chips that do not match the (nicer) specs you outline below.
If we want to enable IP everywhere, we must acknowledge that small
footprint parts are an important part of "everywhere."
That said, I too am in favor of exploring optimized DHCP. It would
provide the flexibility of living in an edge router, or being
centralized. It is a well defined, characterized protocol.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Kris Pister
Sent: Monday, November 09, 2009 6:53 PM
To: Jonathan Hui
Cc: Carsten Bormann; 6lowpan; [email protected]
Subject: [6lowpan] hardware trends, new vs. existing protocols [Re:
4861
usage in LLNs]
+1 in favor of using optimized DHCP if possible (no opinion on 'if
possible'), rather than inventing something new.
As I've shared with several people in private emails recently, it's
pretty clear that lowpan nodes are going to get more capable moving
forward, not less. Why? Radios don't scale down in area when you
scale
CMOS processes. Today's 15.4 single-chip nodes are made in
technologies
that are several (maybe five?) generations behind the cutting
edge. This makes economic sense because the sales volumes don't
support the need for expensive mask sets yet.
When there's a volume application, and someone puts a 5mm2 radio
into modern CMOS, it just doesn't make sense to put 48kB of rom/
flash and 10kB of RAM next to it. You'll put hundreds of kB of rom/
flash, and many tens of kB of RAM, and the radio will still be by
far the biggest thing on the chip.
Even the 48k/10k node from the (very nice) 6lowapp bof presentation
is not up to commercial standards - it's a five year old,
expensive, academic platform - great for it's time, but old.
Single-chip nodes from Jennic, Freescale, etc. have ~200kB ROM/
flash + 128kB RAM, a 32bit processor, and they aren't made in
cutting-edge processes yet either. Life is just going to get
better. Let's try to find the smallest optimized set of *existing*
protocols that serve our needs, that run on the existing new low-
cost hardware (not the old workhorses). Let's invent the absolute
minimum of new "optimized" protocols, because it's not at all clear
to me that we are optimizing the right things at this point. The
less we invent, the broader the set of applications and
applications programmers we address.
ksjp
Jonathan Hui wrote:
On Nov 9, 2009, at 5:50 PM, Carsten Bormann wrote:
Again, entirely getting rid of a function is always the best
optimization.
Can we do that for DAD?
The *need* for DAD is the core question for me. As specified
within 6lowpan-nd now, IPv6 addresses are maintained using a
centralized protocol. That protocol looks and smells like DHCP -
there's request/response, lease times, relays. The whiteboard may
also administratively assign addresses. So in the end, it's not
clear to me why we would need to *detect* duplicates when we
essentially *avoid* them from the beginning.
I've voiced my comment several times over the past 1+ years and
presented a draft that argues for the use of optimized DHCP in
Dublin,
so this is not new from my end. The fact that the current 6lowpan-
nd document has evolved towards using DHCP-like mechanisms is not
an accident. But if what we do is DHCP-like, it would seem to
make sense
to utilize existing DHCP infrastructure rather than defining
something
new.
--
Jonathan Hui
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