Re: [Roll] FW: New Version Notification for draft-thubert-roll-eliding-dio-information-01.txt

["Li Zhao (liz3)" <[e-mail]>]

Hello Pascal,

It looks good if router always need these options. And if a node wants to act as a leaf, it can only request R/D/P.

I'm interested and it's my pleasure to add some sections for AOO-DAO. I'll send it to you later.


Best regards,
Li

On 2019/10/21, 17:58, "Roll on behalf of Pascal Thubert (pthubert)" <[e-mail] on behalf of [e-mail]> wrote:

    Hello Li (and all, please read on as there are additional things we could be doing with the draft listed below)
    
    Let's see below
    
    [Li] Do you mean that child should know ALL option type it needs before select the parent? E.g. one child need R/D/P/M/O to join network but another child only need R/D/P.
    So how does child know this info? Is it pre-defined in child?
    
    <Pascal> The draft assumes that all R/D/P/M/O are always present and always needed. This seems to be the general case. We can make it so that one option would not be present by indicating in the DIO if you think that case is relevant. Please let me know. 
    
    But how will a child know that it does not need an option that is present? Maybe there is something in there that is mandatory to know, e.g., to act as a router. We could say that a node that does not pull all the options can only act as a leaf. Is that what you have in mind?
    
        
        
        2. Is AOO necessary? If DIO can fragment options and don't always send all options, can we use DIO without options to indicate the AOO? 
            The shortest DIO Base Object without DODAGID is only 8 bytes.
        
     <Pascal> AOO is RECOMMENDED to elide the option. A DIO an option elided (no option, no abbreviation) and an unchanged RCSS is perfectly OK. But if an option is elided AND the RCSS is incremented then after a reasonable time-out the children will pull the options to check if they changed and the parent will need to send either the AOO or the option in full or both in which case the RCSS of the AOO wins. It is always possible to place the option in full without a AOO but if it is done with an increased RCSS in the DIO that will mechanically increase the "RCSS of the option" as seen by the children and will cause the whole subdag to pull the option to no avail. 
     
     [Li] Agree, AOO is better than DIO with no option. It’s a nice abbreviated mechanism for RPL Control Message.
           Can we consider to extend AOO for DAO? Maybe put AOO in a new Control Message Options, then DIO/DAO can both leverage it.
           In some case, child will send large DAO packet to parent periodically. E.g. 1. child notifies its capability to parent .2 child has several RPL Target or Transit Information (storing mode?).
    
    <Pascal> Yes we could. Say that the content of a non-storing DAO is fully stable, it could be all replaced by a sequence. Would you be interested in adding that?
    
    If we have to abbreviate elements therein, per target, then we still need to indicate the target so we'll save little, and a different technique like indexing the targets with a BIER bit, would be more efficient.
    
    
    Many thanks again and again Li, for your excellent comments.
        
    Pascal    
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