Re: [Roll] [Anima] ACP RPL profile and dynamics

[Toerless Eckert <[e-mail]>]

Hi Hendrik,

The questions you ask are referrring to details of
rfc8994 that where contributed by Pascal Thubert, and i am
not deep enough into RPL details to answer, so Cc'ing ROLL WG to
maybe get more insight. Michael Richardson might also know...

I do remember that i successfully tested changes in topology of a node
(what you call mobility) in a pre-standard implementation, but i would
know how to relate that to the RPL feature details you mention.

Btw: If there is something coming out of the thread that you
think shows some insufficiency, un-clarity or the like in rfc8994,
i want to encourage you to open an issue on

https://github.com/anima-wg/autonomic-control-plane

so that it can be tracked better.

Cheers
    Toerless

On Tue, Sep 06, 2022 at 09:12:50PM +0200, Hendrik Mahrt wrote:
> Hi,
> 
> I've got some questions regarding the ACP RPL profile. I would be very
> grateful if someone can help me with better understanding how it is supposed
> to work in dynamic scenarios.
> 
> First question: In the ACP RPL profile it is stated that "Nodes SHOULD
> select more than one parent, at least three if possible". But I'm not sure
> how multiple parents are selected by OF0 without nodes being greedy. The OF0
> RFC [RFC 6552] does not contain any information about multiple parents,
> except for a 'backup feasible successor' (Section 4.2.2). But if I
> understand correctly this successor is not 'actively' sought after, i.e.,
> the node does not actively increase its rank to obtain it, as that would
> surely violate the rules of RPL on greediness formulated in RFC 6550 in
> sections 3.7.1 and 8.2.2.4?! Or am I mistaken?
>
> Second question: The ACP RPL profile, as I understand it, features no form
> of global repair or DODAG version increase (except manual intervention by
> admin). How would that work with node mobility (which is mentioned in
> Appendix A.4)? MaxRankIncrease would limit a node's rank movement within a
> DODAG version and is only reset by a version increase, or not? I can also
> imagine other scenarios besides mobility where the maximum rank increase
> might lead to nodes not being able to select a parent in the long run,
> without violating it.
> 
> I also looked at the 'unstrung' RPL implementation for enlightenment but
> found nothing really regarding multiple parents or handling link failures?
> The implementation looks to be WIP though. I might also have missed
> something, in which case I would be grateful if someone can point me to the
> relevant code sections.
> 
> 
> Thank you!
> 
>  Hendrik
> 

-- 
---
[e-mail]