Re: [Roll] AD review of draft-ietf-roll-p2p-measurement-06
"JP Vasseur (jvasseur)" <jvasseur@cisco.com> Thu, 06 December 2012 15:27 UTC
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From: "JP Vasseur (jvasseur)" <jvasseur@cisco.com>
To: "<adrian@olddog.co.uk>" <adrian@olddog.co.uk>
Thread-Topic: [Roll] AD review of draft-ietf-roll-p2p-measurement-06
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Date: Thu, 06 Dec 2012 15:27:46 +0000
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Cc: "<draft-ietf-roll-p2p-measurement.all@tools.ietf.org>" <draft-ietf-roll-p2p-measurement.all@tools.ietf.org>, "<roll@ietf.org>" <roll@ietf.org>
Subject: Re: [Roll] AD review of draft-ietf-roll-p2p-measurement-06
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Hi, Thanks Adrian - I would agree to post a new revision addressing your comment before IETF LC. Thanks. JP. On Dec 5, 2012, at 3:22 PM, Adrian Farrel wrote: > Hi, > > I have done my usual AD review of your document as part of processing > the publication request. This review should be considered alongside > my review of draft-ietf-roll-p2p-rpl as the documents are closely > linked. > > I have a number of questions and minor issues that I would like to > resolve before advancing the documents. > > As usual, all of my comments are up for discussion, but I think that a > new revision will be needed, so I have moved the document into "Revised > I-D Needed" state in the data tracker and will wait for your emails > and/or a new revision. > > Many thanks for your work, > Adrian > > > --- > > As with draft-ietf-roll-p2p-rpl, I would like some discussion in the > Introduction about why this Experimental and what you expect to > discover. I think the text is easier for this document... > > This document provides a mechanism that can be used to determine > whether and how to establish a new point-to-point route in an LLN. > This utility of the mechanism described in this document is, > therefore, dependent on the existence of a protocol mechanism for > establishing P2P routes. [I-D.ietf-roll-p2p-rpl] is targeted at > publication as an Experimental RFC for reasons described in that > document. It makes sense, therefore, for this document also to be > targeted as Experimental. > > As experience is gained using the mechanisms described in > [I-D.ietf-roll-p2p-rpl] it is hoped that the mechanisms described in > this document will also be used, and feedback will be provided to the > ROLL working group on the utility and benefits of this document. > > --- > > I think that "quality" is the wrong word. "Quality" is usually > associated with measures like packet loss, delay, and jitter. I don't > think you are measuring those things, and while I understand why you > say "quality of a route", I think you need some other phrase. > > I think this more like... > > A Mechanism to Record the end-to-end Metrics of a Point-to-point > Route in a Low Power and Lossy Network > > In the Introduction, you have some nice words... > > to measure > the aggregated values of the routing metrics along the existing > route > > --- > > Abstract > > I'm confused :-) > > The document title is very specific to P2P routes. But the Abstract > (deliberately?) does not mention P2P. Section 1 seems to imply that I > could run the mechanisms on any route from origin to target to see if it > is good enough - and that would include routes created using normal RPL. > But section 2 explicitly constrains the mechanism to P2P routes. > > Furthermore, the redefined terminology in 1.1 (see below for my > objection to that!) seem to suggest measuring from an arbitrary origin > to an arbitrary target regardless of whether a P2P route exists. > > Can you: > - unconfuse me > - make sure that the abstract and introduction explain the real > situation > - make sure the document title is accurate > - make sure that the document is consistent > - be careful with terminology (just because you run the mechanism from > A to B in a point-to-point sort of way, doesn't mean that there is a > P2P route from A to B) > > --- > > 1.1 > > Did you really need to redefine these terms instead of use new terms for > new concepts? Given how close the two documents are, it's a shame to > confuse things. > > --- > > 3.1 > > I was going to say... > > Seems like the H flag is not needed since leaving it clear is > semantically equivalent to setting RPLInstanceID=0b10000000 > > Not very important, but you increase the chances of a malformed > message, and you use your last bit that could be reserved for > future use. > > ...but then I read the text lower down about how a transit router > can change the H flag under special circumstances. Now I am confused > because if the H flag setting is changed, surely the rule governing > the RPLInstanceID is broken. > > --- > > 3.1 > > Some of the flag settings that have no meaning dependent on other > flag settings are described as "MUST be set to zero" which is fine. > But should you also say they should be ignored? > > --- > > 3.1 > > I found the description of what goes in the Metric Container Options > inadequate. There should at least be a forward pointer to some section > that describes how this piece of the MO object is constructed, but some > text would help as well. > > --- > > Section 4 > > The Origin MUST discard the MO message if: > > That reads a bit odd. Didn't the Origin just build the message? Why > would it build a message and then discard it? Why not just not build a > bad message? > > --- > > Section 5 > > An Intermediate Router MUST discard the packet with no further > processing if the received MO is not a Measurement Request. > > For clarity and consistency with other paragraphs, can you add... > > i.e., if the T flag is not set to one. > > --- > > Section 7 > > The Origin MUST discard the packet with no further processing ... > ... if the Origin has no > recollection of sending a Measurement Request with the sequence > number listed in the received MO. > > Trying to decide why that is a "MUST". > I guess there are some security/bug considerations. > But are you unduly limiting the Origin implementation to be required to > keep track of the MOs that it sends? > > --- > > Section 7 > > The Origin MUST examine the routing metric objects inside the Metric > Container options to evaluate the quality of the measured P2P route. > If a routing metric object contains local metric values recorded by > routers on the route, the Origin MUST aggregate these local values > into an end-to-end value as per the aggregation rules for the metric. > > That is going too far in the use of "MUST". The Origin can do anything > it likes with the Measurement Reply including discard it, hash it and > use it as a random number, or process it according to policy! I think > what you need is... > > The Origin can use the routing metric objects inside the Metric > Container to evaluate the metrics for the measured P2P route. If a > routing metric object contains local metric values recorded by > routers on the route, the Origin can make use of these local values > by aggregating them into an end-to-end metric according to the > aggregation rules for the specific metric. An Origin is then free to > interpret the metrics for the route according to its local policy. > > --- > > Section 8 > > Question. Can I use this mechanism to find out stuff about the network > that should/would otherwise be private? And could I, as an outside node > do that? > > For example, if I sit next to the network and ping every possible P2P > route, can I find out which nodes are almost out of battery, and which > nodes are key nodes in the topology? Knowing this would help me attack > the network. What are the protections? > > > --- > > 11.2 > You have used [I-D.ietf-roll-p2p-rpl] as a normative reference (at > least for the terminology). > > _______________________________________________ > Roll mailing list > Roll@ietf.org > https://www.ietf.org/mailman/listinfo/roll
- [Roll] AD review of draft-ietf-roll-p2p-measureme… Adrian Farrel
- Re: [Roll] AD review of draft-ietf-roll-p2p-measu… JP Vasseur (jvasseur)