Dale,
Agreed, although what you propose results in the same behaviornasnASN. ASN
is what was chosen.
Thomas

On Friday, September 23, 2016, Dale R. Worley <[email protected]> wrote:

> Thomas Watteyne <[email protected] <javascript:;>> writes:
> > You raise a valid point. There are a couple of points, though, that make
> an
> > "Absolute Slot Number" more favorable compared to an "Absolute Slotframe
> > Number":
> > - if you schedule multiple cells between two nodes in a single slotframe,
> > you want those different transmissions to happen at a different frequency
>
> Although you could construct the schedule so that the nodes have
> different channel offsets for the different slots within the schedule.
>
> > - ASN is used to construct a nonce when securing link-layer frames.
> > Security is such that we never want to re-use the same nonce.
>
> Although you could construct the nonce to be (ASFN * nSlots +
> slotOffset).  And you need to do a construction like that to make sure
> that different nodes with different channel offsets during the same slot
> do not use the same nonce.
>
> I suspect the main reason is that several slotframe schedules of
> different lengths can be active at the same time in one network.
> Keeping a separate ASFN for each schedule would require a lot of work.
>
> Dale
>


-- 
_______________________________________

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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