Re: [Roll] Trickle clarification: (in)consistency

["Julien Abeille (jabeille)" <jabeille at cisco.com>]

Hi Pascal,

Not sure I understand your explanation. In a DIO there are informations
that are global to the DAG and some that are node specific. We use
trickle because we consider DIO sending a consitency problem, hence we
focus on the global information. They come both from parents and childs,
so I would also increment C when hearing from a child. Am I missing
something?

Julien

> -----Original Message-----
> From: roll-bounces at ietf.org [mailto:roll-bounces at ietf.org] On 
> Behalf Of Pascal Thubert (pthubert)
> Sent: vendredi 20 novembre 2009 20:12
> To: Jonathan Hui; Mathilde Durvy (mdurvy)
> Cc: roll at ietf.org
> Subject: Re: [Roll] Trickle clarification: (in)consistency
> 
> Hi Mathilde;
> 
> I agree with Jonathan that we want to avoid redundancy.
> 
> The rank of metric that a node advertises is an information 
> about self that cannot be inferred from the neighbors so it 
> is *not* redundant. If a number of nodes go down at the same 
> time and one does not advertise, then that node will look 
> better and will attract the traffic. It will also attract the 
> neighbors that went down and that will be tempted to reattach 
> to that apparent survivor.
> 
> The information in the DIO that relates to the DAG 
> configuration will be centralized in an option that IS 
> redundant. We could add text that a node that see C of it MAY 
> filter it out from its DIO.
> 
> Finally the new sequence is redundant. I proposed to use it 
> to limit the density of routers using trickle. When you hear 
> C router advertising a new sequence you are entitled to stop 
> being a router for that sequence (stop trickle timer). The 
> trickle timer would then be restarted upon a DIS to serve 
> orphans, and upon a next sequence to redistribute the load.
> 
> Pascal
> 
> >-----Original Message-----
> >From: roll-bounces at ietf.org [mailto:roll-bounces at ietf.org] 
> On Behalf Of
> Jonathan Hui
> >Sent: vendredi 20 novembre 2009 16:41
> >To: Mathilde Durvy (mdurvy)
> >Cc: roll at ietf.org
> >Subject: Re: [Roll] Trickle clarification: (in)consistency
> >
> >
> >Hi Mathilde,
> >
> >On Nov 19, 2009, at 9:24 AM, Mathilde Durvy (mdurvy) wrote:
> >
> >>> - when do we increment C?
> >>
> >> The node MAY increment C when it hears another DIO.
> >>
> >> I think the spec says that a node MAY increment C each 
> time it hears
> a
> >> "consistent DIO for this DAG from a DAG parent". What fields are 
> >> included in the consistency check? If only generic DAG information
> are
> >> checked you might want to look at DIO from non-DAG parents, no?
> >
> >You're right, this text in the draft is incorrect.  There's an 
> >important distinction to make here.  We want to quickly send DIO 
> >transmissions (reset the Trickle timer) whenever 
> *inconsistencies* are 
> >detected.  But you want to suppress DIO transmissions (increment C) 
> >whenever *redundancies* are detected.  While you can detect 
> >inconsistencies by listening to your DAG parent(s), 
> redundancies will 
> >probably come from your siblings/cousins.
> >
> >We are looking to update the text around incrementing C and 
> make what 
> >constitutes a redundancy more precise.
> >
> >--
> >Jonathan Hui
> >
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