Re: [Roll] do we need a dominating set?
Emmanuel Baccelli <Emmanuel.Baccelli@inria.fr> Wed, 18 November 2009 10:06 UTC
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From: Emmanuel Baccelli <Emmanuel.Baccelli@inria.fr>
Date: Wed, 18 Nov 2009 11:05:54 +0100
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Subject: Re: [Roll] do we need a dominating set?
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Hi Stephen, indeed, MPR is what comes to mind in this context. This mechanism is used to identify and maintain connected dominating sets in RFC 5449, RFC 3626, and a slew of soon-to-be RFCs such as draft-ietf-manet-nhdp, draft-ietf-ospf-manet-or, draft-ietf-manet-olsrv2. In order for nodes to see 2 neighbors in the dominating set, you just need to set the value of the MPR_coverage parameter to 2. Emmanuel On Wed, Nov 18, 2009 at 9:07 AM, Pascal Thubert (pthubert) < pthubert@cisco.com> wrote: > Hi Stephen: > > I've seen evidence that " trickle performs fine (well)" for propagating > network invariants. > The state of a node being NOT a network invariant, I see strong evidence > that we are using a very good hammer for pulling screws. > The sequenceNb being a network invariant in an instance, my proposal seems > to be using trickle for what it is good at. > > Pascal > > >-----Original Message----- > >From: sdhags@gmail.com [mailto:sdhags@gmail.com] On Behalf Of Stephen > Dawson-Haggerty > >Sent: mardi 17 novembre 2009 19:15 > >To: Pascal Thubert (pthubert) > >Cc: Philip Levis; roll@ietf.org > >Subject: Re: [Roll] do we need a dominating set? > > > >We have lots of evidence that trickle performs fine (well) in lots of > >settings, including dense ones, when used correctly. This > >"improvement" seems pretty speculative-- do we know that this is > >necessary __in_addition_to_trickle_? I'm only familiar with the MPRs > >in OLSR which seem to perform this function, but there trickle is not > >used. We'd need strong evidence that trickle was insufficient to > >include this. > > > >Steve > > > >On Tue, Nov 17, 2009 at 8:48 AM, Pascal Thubert (pthubert) > ><pthubert@cisco.com> wrote: > >> Hi Phil: > >> > >>>> > >>>> The current RPL draft uses trickle to address density. Trickle has a > >>>> number of fine properties to throttle the control when things are > >>>> stable. > >>>> Still, when an accident occurs, like a parent high in the DAG > >>>> degrades its rank, possibly most of the nodes in the whole network > >>>> will have to reassess their rank and reset their trickle timer. > >>>> My understanding of that process is that it can yield quite a bit > >>>> of activity, that grows with the number of nodes acting as routers. > >>> > >>>Not really, if you have a small redundancy constant. Don't forget, the > >>>number of messages scales logarithmically with density. > >> > >> I understand that the redundancy counter should eliminate redundancies. > >> I can see how DIO options that contain network wide constants can be > >> omitted one the > >> But the fact that a node changes its rank is not a redundancy. > >> Upon the accident up there, all nodes will have to advertise their new > >> rank since they are being used wrongly if they don't. > >> > >>>> What I think is that even if we have trickle, we should be > >>>> considering some control on the density of nodes that act as a > >>>> router. To address that, there's already ample work and large WSN > >>>> deployments that leverage the concept of dominating set. > >>>> A dominating set is a connected set of routers that enables > >>>> connectivity for all > >>>> , that is all nodes in the network is connected to at least one > >>>> member of the dominating set. > >>>> > >>> > >>>I don't think a dominating set is what you mean: a dominating set can > >>>be disconnected. You're talking about a connected dominating set. > >> > >> :) > >> > >>> > >>>> Because we have trickle, such a set does not need to be shrink to > >>>> minimal/optimal. In fact, we'd want that each node in the network > >>>> sees at least 2 members of the dominating set. > >>>> > >>>> Can that be achieved simply? Possibly. > >>>> > >>>> Each time a new sequence is spread, nodes are entitled to reassess > >>>> their need to be a router. When the sequence spreads, a form of > >>>> trickle could be used to decide Not TO advertise self as a router > >>>> and act as a host for the new sequence. > >>>> Like if enough neighbor routers advertise the new sequence before T > >>>> elapse, then there might be no need for self to act as a router. > >>> > >>>This is exactly what trickle is designed to do, with its redundancy > >>>counter. > >> > >> I fail to see that we can do it in the example above. I see that if too > >> many nodes act as router, we'll get many more paths to manage and many > >> more DIOs generated in case of accident. > >> > >> I think we should trickle out the duplicate information in DIO (like DAG > >> config) when many neighbors have already cried out loud that info. > >> But we should also trickle out / redistribute the role of router when > >> opportunity presents itself, that is upon a new sequence. > >> > >> > >>>I thought the major design goal right now to make RPL *less* > >>>complicated? > >> > >> Not having trickle would be a lot less complicated. But also a lot less > >> efficient. So I'm not going there, see? > >> > >> Pascal > >> _______________________________________________ > >> Roll mailing list > >> Roll@ietf.org > >> https://www.ietf.org/mailman/listinfo/roll > >> > > > > > > > >-- > >stephen dawson-haggerty > >http://cs.berkeley.edu/~stevedh > >uc berkeley wireless and embedded systems lab > >berkeley, ca 94720 > _______________________________________________ > Roll mailing list > Roll@ietf.org > https://www.ietf.org/mailman/listinfo/roll >
- Re: [Roll] do we need a dominating set? Michael Richardson
- Re: [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Philip Levis
- [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Maxence Dalmais
- Re: [Roll] do we need a dominating set? Philip Levis
- Re: [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Stephen Dawson-Haggerty
- Re: [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Emmanuel Baccelli
- Re: [Roll] do we need a dominating set? Philip Levis
- Re: [Roll] do we need a dominating set? Philip Levis
- Re: [Roll] do we need a dominating set? Michael Richardson
- Re: [Roll] do we need a dominating set? Philip Levis
- Re: [Roll] do we need a dominating set? JP Vasseur
- Re: [Roll] do we need a dominating set? Pascal Thubert (pthubert)
- Re: [Roll] do we need a dominating set? Philip Levis