Subject: [Roll] Unique destinations and the protocol survey draft

From: <[email-masked]>
Date: Thu, 20 Nov 2008 17:29:32 +0100

The protocols survey document states

"However, as many low-power and lossy networks behave principally as
data collection networks and principally communicate through routers to
data collection points in the larger Internet, scaling with the number
of such collection points is reasonable.  Protocols whose state scales
with the number of destinations pass."

I can give several counter examples.

Home automation very often involves control - switching lights on and
off, opening and closing shutters.
I can make the same case for Building automation: lights, heating are
turned on and off or turned on and down.

Don't know much about Industrial automation. 
The claim is probably most valid for Urban networks except for one very
important case, AMI.
Smart energy solutions involve demand response and load control. This
implies messages from the utility to the electric meter. So here again
we have a large number of unique destinations.

It is entirely possible that the data traffic for commands is much
smaller than reporting traffic. However the number of unique
destinations is not orders of magnitude less than N and will very likely
be greater than L.

Madhu

_______________________________________________
Roll mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/roll

---

From: Philip Levis <[email-masked]>
Date: Thu, 20 Nov 2008 10:21:23 -0800

On Nov 20, 2008, at 8:29 AM, <giyyarpuram.madhusudan@orange- 

> destinations is not orders of magnitude less than N and will very  

Madhu,

I fear you might be misinterpreting that paragraph. The point is not  
to say that all apps have a small D, but rather that apps which do  
have a small D should not have to pay a big price to maintain many  
unused routes. Apps that need many routes of course need to maintain  
them. That's why it says "many" and not "all." The "many" is big  
enough that we can't just ignore it.

Does that make sense?

Phil

---

From: <[email-masked]>
Date: Fri, 21 Nov 2008 11:58:02 +0100

>>However, as many low-power and lossy networks behave principally as 
>> data collection networks and principally communicate through routers 
>> to data collection points in the larger Internet, scaling with the 
>> number of such collection points is reasonable.  Protocols whose
state 
>> scales with the number of destinations pass."

>> The claim is probably most valid for Urban networks except for one 
>> very important case, AMI.

>> destinations is not orders of magnitude less than N and will very 
>> likely be greater than L.
>> Madhu

> Madhu,
> I fear you might be misinterpreting that paragraph. 
> The point is not to say that all apps have a small D, but rather that
apps 
> which do have a small D should not have to pay a big price to maintain
many 
> unused routes. Apps that need many routes of course need to maintain
them. 
> That's why it says "many" and not "all."  The "many" is big enough
that we can't just ignore it.
> Phil
Phil,
I agree that apps with small D should not have to pay the price for big
D apps. 
However there seems to be the supposition that the small D is the
"general" case and the big D
is the exception. Hence claims like O(D) scaling passes or O(D) route
updates passes.
It seems to me that the trend in "many" apps is towards more active
contol as opposed to pure data
collection. This has been true in AMR which is becoming more AMI. 
Also this is not a just a sensor/actuator ratio. Even for sensors that
only send reports one may want
to send configuration commands that change the frequency of reporting or
request frequent updates for a
short period of time or change the threshold for events.
However I would buy the argument that data collection traffic will be
much higher than 
command/query/configure traffic. So perhaps it is a question of
optimizing for data collection 
and shifting the burden for command traffic onto the originator (such as
source routing).
Madhu