My understanding is that the problem in the permuted schedule arises during 
COJP_REKEYING_GUARD_TIME after nodes in the network started using the new keys, 
but have still kept the old key in case someone has not yet switched. When 
coupled with a rekeyed permutation key to calculate the schedule, this means 
that during COJP_REKEYING_GUARD_TIME a node would need to follow two schedules, 
one with the old permutation key and one with the new one. The problem in 
following two schedules for COJP_REKEYING_GUARD_TIME is that 
draft-tiloca-6tisch-robust-scheduling-01 recommends both the slotOffset and the 
channelOffset be permuted so that it may occur that there can be a collision in 
slotOffset between the new and the old schedule.

The problem that draft-tiloca-6tisch-robust-scheduling solves seems to be the 
predictability of the channel on which a transmission is going to take place. 
With that in mind, I have second thoughts about the recommendation on permuting 
the slotOffset, especially taking into account that this will break any 
scheduling function that optimizes for latency, as discussed in Section 6.3.

Mališa


> On 4 Apr 2019, at 17:40, Michael Richardson <m...@sandelman.ca> wrote:
> 
> Can you see how the old/new key issue interacts poorly with the permuted
> schedule?

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