Re: [6lowapp] [6lowpan] hardware trends, new vs. existing protocols [Re: 4861 usage in LLNs]

["Pascal Thubert (pthubert)" <[e-mail]>]

Hi Kris:

Nothing says that DHCP cannot be used in that world, for what DHCP is
for. 
The question is whether we can use DHCP as ND. 
My short answer is no, these are 2 different models, like a push and a
pull.
I agree with Jonathan that there are good reasons why the flows in
6LoWPAN ND look so much like DHCP.
Where I disagree is pushing the analogy as far as getting confused
between the 2.

Pascal

>-----Original Message-----
>From: [e-mail] [mailto:[e-mail]] On
Behalf Of Kris Pister
>Sent: mardi 10 novembre 2009 03:53
>To: Jonathan Hui
>Cc: Carsten Bormann; 6lowpan; [e-mail]
>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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