Re: [Roll] How to react if Trickle Interval > Default Lifetime

Dear Cenk,

In Contiki we send periodic multicast DIS until the node has joined any DAG.
After that, one thing you can do if enable "probing", which will
periodically send a unicast DIS to your preferred parent (and also cover
other candidates neighbors, to keep link estimates up-to-date).

In general wouldn't it be the expected practice to advertise trickle
parameters that never surpass the default lifetime?

Simon

On Mon, May 2, 2016 at 9:25 PM, Cenk Gündogan <cnkgndgn@gmail.com> wrote:

> Dear RPL Veterans,
>
> I recently came across the question of how a RPL router may react,
> if a parent's default lifetime (and unit -- specified in the DODAG Conf.
> Opt.)
> is surpassed by the parent's continuously rising trickle interval?
>
> Without any action from the children, I would assume that the upward link
> to
> the parent would time out before the next DIO arrives to refresh the
> lifetime,
> hence breaking the child -> parent relation.
>
> Implementations seem to handle this case very differently..
>
> * The RPL implementation of RIOT uses unicast DIS messages to request a
> one-shot DIO
> from a parent that has a link which is about to expire.
> * From what I could gather in [1], Contiki also seems to send unicast DIS
> messages randomly in an interval of 30~55 seconds (Please correct me if I
> am wrong).
> * In an off-list discussion with Michael, I learned that unstrung is e.g.
> handling
> this case by not letting the Trickle interval exceed the default lifetime
> (Again, please correct me if I am wrong).
>
> I couldn't find any hints regarding this situation in RFC6550.
> Is there actually an obvious way to handle this, but I am just not seeing
> it?
>
> Best,
> Cenk Gündoğan
>
> [1]
> https://github.com/contiki-os/contiki/blob/master/core/net/rpl/rpl-timers.c
>
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