Re: [manet] NHDP: Link quality based on seq-num

[Thomas Heide Clausen <ietf at thomasclausen.org>]

On Nov 10, 2009, at 12:02 AM, Teco Boot wrote:

> Hi Ulrich,
>
> > -----Oorspronkelijk bericht-----
> > Van: Ulrich Herberg [mailto:ulrich at herberg.name]
> > Verzonden: maandag 9 november 2009 23:41
> > Aan: Teco Boot
> > CC: Dearlove, Christopher (UK); manet at ietf.org
> > Onderwerp: Re: [manet] NHDP: Link quality based on seq-num
> >
> > Teco,
> >
> > On Mon, Nov 9, 2009 at 11:31 PM, Teco Boot <teco at inf-net.nl> wrote:
> > > What if someone defines a reliable transport and suppress
> > > repeating messages?
> >
> > In that case, that mechanism of using packet seq. numbers would not
> > work. But I think this is okay, since the NHDP draft does not mandate
> > this mechanism. If one decides to use packet sequence numbers for
> > indicating lost packets, one probably has to assume a non-reliable
> > transport transport protocol such as UDP.
>
> You missed my point.
> The protocol would suppress the repeated info.

Then I do not understand. Your L2 (or "something-behaving-as-L2")  
below IP is reliable. That's fine, you'll get 100% of packets across.  
A great L2 and a great feat if you can do reliable broadcast to an  
unknown recipient set (I'd like to learn more if you have one at hand).

> > > Are we sure we want to use missing sequence numbers as
> > > indication of missed packets?
> >
> > No, we don't want to mandate it. It is just *one* possible way, under
> > certain assumptions (no reliable transport protocol).
>
> But it is an impossible way, as defined today in the spec.

How so? Your L2 does not lend itself to "counting packets" - so you  
won't, you'll use something else (more appropriate to your L2) for  
establishing the quality.

This is not only enabled by the spec, but even recommended.

> > > What if other reasons caused the loss, e.g. tail drop during
> > > congestion caused by the MANET protocol itself?
> >
> > Well, in that case the router will face problems anyway, since it  
> > does
> > not receive control traffic any more.
>
> And send more traffic. See a nearby museum for what can happen if a  
> system
> is speeding up its own explosion.

I think that's an inappropriate reference.

I also think that it's an inappropriate and incorrect characterization  
of what NHDP would do....

Thomas


> Teco.
>
>
> > Ulrich
> >
> > > Teco.
> > >
> > > > -----Oorspronkelijk bericht-----
> > > > Van: manet-bounces at ietf.org [mailto:manet-bounces at ietf.org] Namens
> > > > Ulrich Herberg
> > > > Verzonden: maandag 9 november 2009 22:11
> > > > Aan: Dearlove, Christopher (UK)
> > > > CC: manet at ietf.org
> > > > Onderwerp: Re: [manet] NHDP: Link quality based on seq-num
> > > >
> > > > On Mon, Nov 9, 2009 at 8:03 PM, Dearlove, Christopher (UK)
> > > > <Chris.Dearlove at baesystems.com> wrote:
> > > > > My, not fully worked out, thought is that per interface
> > > > > packet sequence numbers should be allowed, or even
> > > > > preferred. That leaves a procedural issue of how to get
> > > > > from where we are to where we want to be.
> > > >
> > > > I agree that we should allow packet sequence numbers per  
> > > > interface. At
> > > > the moment, I cannot think about a good reason for not preferring
> > > > them, but maybe there is...
> > > >
> > > >
> > > > Ulrich
> > > > _______________________________________________
> > > > manet mailing list
> > > > manet at ietf.org
> > > > https://www.ietf.org/mailman/listinfo/manet
>
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