Subject: Re: [Roll] FW: New I-D on composite routing metrics

From: Mischa Dohler <[email-masked]>
Date: Thu, 29 Sep 2011 10:22:53 +0200

Hi Panos and Theodore,

I have gone through your updated draft 
http://tools.ietf.org/html/draft-zahariadis-roll-metrics-composition-01. 
It reads much better now and seems to have addressed the worries issued 
by Cedric and Pascal before.

I personally fully second your findings on the need for composite 
routing metrics, facilitating in a sense some QoS framework over LLNs. I 
also like that you corroborate this by some theoretical framework on 
routing algebra (something coming a little too short in this WG so far).

I would welcome however that you stated more clearly in the introduction 
that prior ROLL documents, notably
- "draft-ietf-roll-minrank-hysteresis-of",
- "draft-ietf-roll-routing-metrics" and
- "draft-ietf-rollof0"
define objective functions composed of one metric, but that the recently 
issued
-"draft-ietf-roll-applicability-ami-03"
clearly states the need for using more than one to get practical 
deployments viably going.

It would be great if you could attend an upcoming IETF meeting to make a 
case for your draft which I am sure the entire WG would greatly profit from.

Thanks and kind regards,
Mischa.
______________________________

Dr Mischa Dohler

Head of [IQe], CTTC, Barcelona
www.cttc.es/home/mdohler

CTO Worldsensing, Barcelona
www.worldsensing.com
______________________________

[Roll] ÎÏÎÏ: Re: FW: New I-D on composite routing metrics

     To: C Chauvenet <c.chauvenet at watteco.com>
     Subject: [Roll] ÎÏÎÏ: Re: FW: New I-D on composite routing metrics
     From: Panos Trakadas <trakadasp at yahoo.gr>
     Date: Sun, 7 Aug 2011 10:58:21 +0100 (BST)
     Cc: roll at ietf.org
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Hi Cedric,
We will take into consideration your comments in the newer version of 
our draft.
Furthermore, we are developing RPL for JSim simulation platform 
(hopefully it will be ready by mid August).
We could benefit from this simulator towards many directions such as 
evaluation of several QoS composite metrics, experimentation with 
multiple application-specific instances, as well as accurate estimation 
on hysteresis threshold.
Best regards,
Theodore and Panos.

From: C Chauvenet <c.chauvenet at watteco.com>;
To: Panos Trakadas <trakadasp at yahoo.gr>;
Cc: zahariad at teihal.gr <zahariad at teihal.gr>; roll at ietf.org 
<roll at ietf.org>;
Subject: Re: [Roll] FW: New I-D on composite routing metrics
Sent: Sat, Aug 6, 2011 2:29:35 PM

Hi,

See inline.

Le 5 aoÃt 2011 Ã 01:58, Panos Trakadas a Ãcrit :

 > Dear Cedric,
 >
 > We believe that the definition of "order relation" is correct: the 
order relation is used by the OF to compare link/node weights along the 
path (equivalently, metric values) and select parent node.
 >
 >
 > [C.C] I Agree with your definition.
 >
 > As an example, consider the case where the ETX is aggregated along 
the traversed path. If node A receives DIO messages from nodes B and C 
(potential parents) with ETX values of 2.5 and 3.2, respectively, then 
the order relation will help selecting node B (advertising the minimum 
value of ETX) as the parent of node A.
 > In this concept, your comment is right; the order relation of LQL 
must be minimum (and not maximum). Please consider it as a typo.
 >
 > [C.C] OK
 >
 >
 > Regarding link-color comment: Apart from being used as a 10-bit flag 
field (e.g. for indicating the encrypted links, as described in 
rpl-metrics draft), link color may be used to indicate the number of 
nodes along the path transmitting at a specific radio channel; in this 
way interference can be reduced by selecting transmission in the "least 
occupied" channel. In this case, the order relation must be "minimum" 
and the domain is integer.
 >
 > [C.C] I think that the confusion is greatly due to the very wide 
range that the link color metric may cover. You example of the usage of 
this metric is interesting, but many others usage may be possible, and 
so an global order relation seems difficult to find for this metric.
 >
 > In general, we will re-format Table 1, following the metric 
description in rpl-metrics draft. Also, we will replace words 
"minimum"/"maximum" in the "order relation" column by "less-than" and 
"greater-than" in accordance to the order relation definition.
 >
 > [C.C] I agree that it would increase the readability.
 >
 > Before submitting this draft, there was a discussion on whether we 
should include examples and formulas in this initial version of the 
document; it seems that our decision was wrong... We will be happy to 
include examples and formulas to improve readability of this draft.
 >
 > [C.C] Nice. I think this would provide precious guidelines for 
readers, and speed up some RPL design.
 >
 > Finally, we think that "hysteresis" can provably improve RPL 
performance, and thus it will be included in this draft. To be honest, 
there is a "hidden" phrase: "...and if the first component values are 
equal *or differ less than a predefined threshold*..." (section 4.1, 
first sentence) indicating our effort to include hysteresis in this 
draft. We will give more emphasis on that point.
 >
 > [C.C] I noticed that reference, but it should be worth to explicitly 
speak about it. I also agree that the Hysteresis mechanism defined in 
the MRHOF draft greatly improve the stability of the topology and should 
be highly recommended. BTW, some guidelines about how to determine the 
good threshold value would be interesting.
 >
 > Thanks for your valuable comments,
 > Panos.
 >
 > CÃdric.
 >
 >
 > --- ÎÏÎÏ ÎÎÏ., 03/08/11, Î/Î C Chauvenet <c.chauvenet at watteco.com> 
ÎÎÏÎÏÎ:
 >
 >
 >     ÎÏÏ: C Chauvenet <c.chauvenet at watteco.com>
 >     ÎÎÎÎ: Re: [Roll] FW: New I-D on composite routing metrics
 >     ÎÏÎÏ: "zahariad at teihal.gr" <zahariad at teihal.gr>
 >     ÎÎÎÎ.: "TRAKADAS PANOS" <trakadasp at adae.gr>, "roll at 
ietf.org" <roll at ietf.org>
 >     ÎÎÎÏÎÎÎÎÎÎ: ÎÎÏÎÏÏÎ, 3 ÎÏÎÎÏÏÏÎÏ 2011, 18:46
 >
 >     Hi Theodore,
 >
 >     I found your draft interesting and it gave me some useful 
guidelines for metric's design.
 >
 >     I've several comments on this :
 >
 >     I fail to understand well the "Order Relation" you use in Table 1.
 >     The definition of "metric order relation" given on page 4 doesn't 
really helped me.
 >     Could you help me understand the Order Relation column in the table?
 >
 >     In this table in particular (Figure 1):
 >
 >         - Could you precise your view of the  Link-Color metric (Why 
is it in the integer domain, why the order relation in "minimum" ?).
 >
 >         - As far as I understand the Order Relation, it seems that 
the LQL order relation should not be "maximum" but rather "minimum" 
(same relation as ETX, excluding the 0 value).
 >
 >
 >     More generally, I would be happy to see in the document some 
formulas examples for metric computation, or maybe some guidelines.
 >
 >     Some example of metrics composition would also be great (You 
mention one in your draft with is ETX + RE (remainging Energy). Do you 
have some idea about other set of metric that would be interesting to bind ?
 >
 >     I finally think that it should be worth to add some content about 
the mechanisms that aim to deal with metric's dynamics (Multi Threshold, 
EWMA, Low pass Filters, ...). Some of them are mentioned at the end of 
the rpl metric draft.
 >
 >     Best,
 >
 >     CÃdric.
 >
 >     Le 2 aoÃt 2011 Ã 02:55, Theodore Zahariadis a Ãcrit :
 >
 >     > Dear all,
 >     > My colleague Dr. Panos Trakadas and myself are working on an 
EC-funded
 >     > research project, called VITRO (Virtualized Distributed 
platform of Smart
 >     > objects - http://www.vitro-fp7.eu/), which has adopted RPL as 
the primary
 >     > routing protocol and we are currently performing some 
simulations and tests.
 >     >
 >     > By monitoring roll, we have noticed that three (sorry if we 
have missed any)
 >     > I-D are discussed in the ROLL WG 
(draft-ietf-roll-minrank-hysteresis-of,
 >     > draft-ietf-roll-of0, draft-gnawali-roll-etxof), defining RPL 
Objective
 >     > Functions related to a single routing metric (either hop-count 
or ETX).
 >     >
 >     > In VITRO, each sensor may be part of many virtual networks 
(even from
 >     > different administrative domains) and must be able to 
concurrently support
 >     > multiple user requests even with contradicting QoS 
characteristics. It is
 >     > obvious that in such cases, a composite routing metric is of great
 >     > importance.
 >     >
 >     > In draft-zahariadis-roll-metrics-composition-00
 >     > 
(http://datatracker.ietf.org/doc/draft-zahariadis-roll-metrics-composition/)
 >     > , we aim at specifying the guidelines for designing efficient 
composite
 >     > routing metrics to be applied at RPL routing protocol.
 >     >
 >     > We would be happy to receive your comments
 >     >
 >     > Best Regards,
 >     > Theodore Zahariadis
 >     >
 >     >
 >     > ------------------------------------
 >     > Ass. Prof. Theodore Zahariadis, PhD
 >     > Technological Educational Institute of Chalkida
 >     > Psachna, Chalkida, Greece
 >     > Tel:             +30 22280 99550      ,             +30 
6932495045
 >     > Skype: theodore.zahariadis
 >     >
 >     >
 >     > _______________________________________________
 >     > Roll mailing list
 >     > Roll at ietf.org
 >     > https://www.ietf.org/mailman/listinfo/roll
 >
 >
 >     _______________________________________________
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