Re: [6tisch] follow up LIST cmd 6P

[Thomas Watteyne <[e-mail]>]

Tero,

Thanks for the explanation.

I looks like a single sentence in the 6P draft banning piggybacking
non-6P IEs would make the problem disappear, no?

Thomas

On Thu, Sep 8, 2016 at 2:46 PM, Tero Kivinen <[e-mail]> wrote:

> Thomas Watteyne writes:
> > I agree no functionality is lost if the mote must return at least one
> cell.
> > But it's a race condition: what happens if there are so many other IEs
> that
> > there is no space at all, even for a single cell.
>
> If we have that many other IEs, then we do have other issues too. I
> mean, the examples we have given are using really tiny frames,
> something like 30 octets. The default frame size is 127, so I do not
> really expect it to lower the number of cells down to 4, but closer to
> 20...
>
> > And while I am not doubting that many more IEs will be invented for many
> > different things, I'm skeptical when you explain that all of these will
> > happily be piggybacked in 6P messages. Surely there must be a sentence in
> > 15.4-2015 that explains the rules for piggybacking?
>
> Nope. All of that is left for upper layers to decide. IEEE
> specifications just define the IEs, and how they are encoded, and in
> latest version it also includes in which frame types they are
> typically used, but when to send them is mostly left for
> implementations to decide.
>
> In some cases it do say that certain IEs shall be piggybacked, like
> Time Correction IE and Link Margin IE (from 802.15.4q). Those both are
> in Enhanced ACKs so they are not an issue here, but for example the
> 802.15.10 (mesh networking) will put some routing etc IEs on all
> frames. Fortunately it is most likely not used with 6tisch.
>
> Anyways mostly this is just in case someone adds more and more IEs
> that do things on frames. Currently there is not that many that are
> added in the data frames, or at least there is no defined use for
> them...
>
> This issue is much bigger on the Enhanced Beacons, as there is so many
> different IEs you can put there.
> --
> [e-mail]
>



-- 
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Thomas Watteyne, PhD
Research Scientist & Innovator, Inria
Sr Networking Design Eng, Linear Tech
Founder & co-lead, UC Berkeley OpenWSN
Co-chair, IETF 6TiSCH

www.thomaswatteyne.com
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