Re: [manet] LOADng-06

[Ulrich Herberg <[e-mail]>]

Hi Bo,

On Mon, Oct 22, 2012 at 6:39 PM, Bo Berry <[e-mail]> wrote:

> Hi Alex
>
> For those of us that have not have the opportunity to follow
> the Loadng discussions, could you please describe the similarities
> and the unique differences of Loadng relative to Dymo.  I'm aware
> of the discussions about lousy nets and manets, but less between
> the two protocols.
>
> I think this would help everyone on the WG understand the benefits.
>


I agree with that, and it is a fair question to ask. Let me try to list a
few differences, others may chime in with more.

First the commonalities:
 - Both are reactive protocols, based on AODV, with the intended status of
"Proposed Standard" (AODV is "Experimental"). The MANET charter lists that
the WG has to come up with a std. track reactive protocol. Essentially, in
a reactive protocol, routes are requested "on-demand" (i.e. when there is
data traffic and no route exists for the destination of the data packet).
Therefore, you will see similar message types in both protocols (Route
Requests, Route Replies, and Route Errors), and essentially the same basic
mechanism.
- Both are applicable to MANETs (see also below for your next question),
and both support RFC5444. LOADng is decoupling the mechanism from the
message format; RFC5444 is mapped to the mechanism, but other message
formats could easily be specified (e.g., with a more compressed message
format for extremely limited links in terms of bandwidth).

Now some differences:
- Most importantly: LOADng has achieved what DYMO failed to do: to gather
broad industrial support from several large companies, several large-scale
deployments with several thousands of nodes, LOADng has an updated MIB
document, and documented interoperability test of at least four recent
implementations.
- Part of the reason, I believe, is that the writing style is very
different. LOADng has a more algorithmic way of writing. That's immediate
to see when you compare section 5.3 of DYMO with section 12 of LOADng. It
is, IMO, much harder to implement DYMO. The goal for LOADng was to make it
so straight forward to implement that an undergrad student could take the
spec, spend a few days implementing it and have a reasonable and
interoperable implementation. I have implemented LOADng in one day, based
on the specification.
- There are multiple optional features in DYMO that have deliberately not
been included in LOADng (expanding ring multicasts, intermediate RREPs,
precursor lists etc). The reason was the following: in an experimental
protocol (AODV) it is fine to have many options, in order to explore
whether they are useful. We have that experience now with AODV. For some of
the options, such as iRREP, it has not been shown over the last decade that
they are of general use. In some cases, they may be beneficial, but not in
general. Also, they make it very hard to provide end-to-end security.
LOADng kept the mantra of a small, slim, and efficient protocol. Having
many options makes it hard to assure interoperable devices out of the box,
in particular if there is no negotiation of capabilities.
Moreover, reactive protocols are often used in cases where memory is an
extremely scarce resource, and where proactive protocols cannot be used.
That makes a slim design preferable, IMO, for such protocols.
- LOADng may be used in other layers as L3, e.g. as mesh-under protocol.
- LOADng supports optimized broadcasting mechanisms such as MPR flooding
- There is no Route Reply ACK in DYMO; this is part of LOADng to verify
bidirectionality of links; as in wireless channels, links are rarely
symmetric.


>
> Looking at the Tools page, the draft was first submitted October 24, 2011,
> draft-clausen-lln-loadng-00.  The title was, "The LLN On-demand Ad hoc
> Distance-vector Routing Protocol - Next Generation (LOADng)."  The
> abstract included the statement "The protocol is derived
> from AODV and extended for use in LLNs".
>
> Then in the July 14, 2012 version, draft-clausen-lln-loadng-05, the
> line "The protocol is derived from AODV (RFC3561) and extended for
> use in LLNs." was removed.  This version also supported RFC 5444.
>
> The draft posted tonight, October 22, 2012, draft-clausen-lln-loadng-06,
> for the most part changes "Low power and Lossy Networks (LLN)"
> references to "Mobile Ad hoc NETworks (MANETs)."
>


The draft started out from where the deployments exist, which some call
LLNs. However, as a basic reactive protocol, LOADng also covers the more
general MANET case that includes a wider ranger of resources (from
extremely constrained to not-so-constrained) and mobility. In particular,
by supporting RFC5444 it fits well in the MANET architecture and the
surrounding security extensions, flooding optimizations and TLVs etc. for
RFC5444.

I hope I could shed some light on that question. I invite you to read both
drafts, there is probably more to say here.

I won't go into details here, but most of the discussions we had were not
so much about technical issues, but about procedural. LOADng has started
when DYMO was stalled for more than 2 years. I think we have a well mature
document, supported by strong industry backing and running code. The latter
is crucial in the IETF.

Best regards
Ulrich




>
> Thanks
> -Bo
>
>
>
> On Oct 22, 2012, at 8:03 PM, Axel Colin de Verdière wrote:
>
> > Dear all,
> >
> > we have updated LOADng, to make it clear that it is in scope and charter
> for MANET. Unfortunately, it is only a minor revision of the technical
> content, since we have been in discussions with the DYMO authors and the WG
> leadership for several months on how to proceed with the reactive protocol
> in MANET. The chairs will likely reply very soon to the list with an
> outcome of the discussion.
> >
> > Best regards,
> >
> > Axel Colin de Verdiere
> >
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