Re: [manet] Reactive Protocol Situation

[Ulrich Herberg <[e-mail]>]

Hi Phil,

maybe we should open a separate email thread about RPL
and draft-clausen-lln-rpl-experiences (and probably not in this WG).

Best
Ulrich

On Thu, Nov 1, 2012 at 9:45 AM, Philip Levis <[e-mail]> wrote:

> On Nov 1, 2012, at 9:27 AM, Dearlove, Christopher (UK) wrote:
>
> > They can be good evidence of the failure of protocols ;)
> >
> > But what is clear to me is that one important issue (and another of my
> posts is attempting to both be more precise, as well as going elsewhere) is
> the handling of unidirectional links. So any good evidence needs to
> consider those.
>
> Since communication in wireless is rarely binary, I think the more common
> term is asymmetric links. I'm confused; I don't believe that unit disc
> models capture asymmetric links. Is the implied statement that RPL doesn't
> properly handle asymmetric links but LOADng does? I think this came up in
> draft-clausen-lln-rpl-experiences and there was some discussion on the ROLL
> list about it. The neighbor set in RPL is defined in 8.2.1:
>
> "First, the candidate neighbor set is a subset of the nodes that can be
> reached via link-local multicast."
>
> then in DIO processing (8.2.3.1) it reads:
>
> "As DIO messages are received from candidate neighbors, the neighbors may
> be promoted to DODAG parents by following the rules of DODAG discovery as
> described in Section 8.2."
>
> I want to be clear here; I haven't read deeply about LOADng, thought about
> it much, or experimented with it at all. So I have zero to say about
> LOADng's strengths and weaknesses.
>
> But just because somebody publishes (and republishes) a draft saying
> something doesn't mean it's true. There are, in my opinion, some very valid
> points in draft-clausen-lln-rpl-experiences that relate to fundamental
> design decisions in RPL. For example, I think that the issues raised about
> the state requirements of floating DODAGs and RPL message fragmentation are
> valid and reasonable and something we need to look at.
>
> However, there are others that are the result of naive mistakes anyone can
> make when implementing any wireless routing protocol, such as link
> asymmetry and protocol convergence. Unfortunately the draft doesn't
> distinguish the two. Implementing a protocol poorly then saying it doesn't
> work isn't particularly meaningful. As I said in Paris, I thought the draft
> is valuable because it outlines many of the basic mistakes one makes the
> first time you try implementing a wireless routing protocol.
>
> Phil
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