Re: [Roll] Review of draft-ietf-roll-enrollment-priority-04

[Konrad Iwanicki <[e-mail]>]

Hi Pascal,

On 10/08/2021 22:45, Pascal Thubert (pthubert) wrote:
>> Le 10 août 2021 à 19:42, Michael Richardson <[e-mail]> a écrit :
>> Pascal Thubert (pthubert) <[e-mail]> wrote:
>>>> 3. Even if the this approach were covered in the draft, it still has
>>>> some issues, which I was about to explain but the new version of the
>>>> draft appeared.
>>
>>> Yes we need to sync. I think Michael still has in mind that the minimum
>>> is incremented down. That was the initial idea.
>>
>> So there are three possible things, I think:
>> 1) root expresses constant to entire DODAG
>>    each 6LN expresses it's local increment
>>
>> 2) root expresses base value, 6LNs increment it
>>
>> 3) root expresses base value, 6LNs increment or decrement it
>>
>> I can't see a situation where there is a need to decrement it.
>> Is there someone who has a use case that needs that?
>>
>> I thought that (2) was simplest in terms of code.
> 
> It’s not that simple since a node cannot infer what the value really means.
> 
> With 1) plus a sequence, the value has a global meaning and the most recent value is the truth. Nodes can take a same logical decision regardless of their location in the network, eg jump onto another disaggregation to rebalance.
> 
> With 2) different parents may give different values for the same sequence. Which should our node pick? The one from the preferred parent? Or should the node reparent to the best offer? There’s complexity and consequences to that decision of picking one value. And then no way to know the abstract desirability of the next dodag since the value from the root is lost.

Let me reply with the issues and a possible way of addressing some of 
them in the e-mail I have already been writing for a while.

Best,
-- 
- Konrad Iwanicki.