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

"Li Zhao (liz3)" <liz3@cisco.com> Sat, 26 October 2019 00:54 UTC

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From: "Li Zhao (liz3)" <liz3@cisco.com>
To: Routing Over Low power and Lossy networks <roll@ietf.org>
Thread-Topic: [Roll] FW: New Version Notification for draft-thubert-roll-eliding-dio-information-01.txt
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Archived-At: <https://mailarchive.ietf.org/arch/msg/roll/63ycJNoCO7OjwsnJMku4nCpEfHU>
Subject: Re: [Roll] FW: New Version Notification for draft-thubert-roll-eliding-dio-information-01.txt
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Agree. We can use MOPEX to indicate the capability. Hope that MOPEX can move on in 106.

Best regards,
Li

On 2019/10/25, 21:18, "Roll on behalf of Pascal Thubert (pthubert)" <roll-bounces@ietf.org on behalf of pthubert@cisco.com> wrote:

    It's now merged, Li.
    
    We'll probably need a capability to indicate that the abbreviations are supported, in particular for DAO.
    
    All the best
    
    Pascal
    
    > -----Original Message-----
    > From: Roll <roll-bounces@ietf.org> On Behalf Of Li Zhao (liz3)
    > Sent: jeudi 24 octobre 2019 08:56
    > To: Routing Over Low power and Lossy networks <roll@ietf.org>
    > Subject: Re: [Roll] FW: New Version Notification for draft-thubert-roll-eliding-
    > dio-information-01.txt
    > 
    > Hello Again Pascal,
    > 
    > I've written it in https://github.com/roll-wg/eliding-dio-information/pull/2.
    > Could you please take a look?
    > 
    > Best regards,
    > Li
    > 
    > On 2019/10/24, 11:20, "Roll on behalf of Li Zhao (liz3)" <roll-bounces@ietf.org
    > on behalf of liz3@cisco.com> wrote:
    > 
    >     Hello Pascal,
    > 
    >     Add new flag in DAO is a better option. I'll write it down later.
    > 
    >     Best regards,
    >     Li
    > 
    >     On 2019/10/23, 20:57, "Roll on behalf of Pascal Thubert (pthubert)" <roll-
    > bounces@ietf.org on behalf of pthubert@cisco.com> wrote:
    > 
    >         Hello Li
    > 
    >         The AOO abbreviates an option. It is strange to me to use it to abbreviate a
    > full RPL control message. And I do not think we need that.
    > 
    >         Currently there should not be a DAO with no option in it. So we do not
    > really have a collision with RFC 6550. Still I understand your point and I'd be
    > happy to add a flag in the DAO to say that the DAO is globally abbreviated.
    > 
    >         Would that work for you?
    > 
    >         Pascal
    > 
    >         -----Original Message-----
    >         From: Roll <roll-bounces@ietf.org> On Behalf Of Li Zhao (liz3)
    >         Sent: mercredi 23 octobre 2019 04:01
    >         To: Routing Over Low power and Lossy networks <roll@ietf.org>
    >         Subject: Re: [Roll] FW: New Version Notification for draft-thubert-roll-
    > eliding-dio-information-01.txt
    > 
    >         Hello Pascal,
    > 
    >         The reason why we need AOO in DAO is to distinguish whether this DAO
    > carries elide options.
    > 
    >         Otherwise, there is a compatibility issue if the behavior for DAO with no
    > option changes. Because currently when node receives this DAO with no option,
    > it does nothing according to RFC6550.
    > 
    >         For the 2 targets case, can we use Abbreviated Option as 0x00 or 0xff to
    > indicate all options unchanged?
    > 
    >         Best regards,
    >         Li
    > 
    >         On 2019/10/22, 23:44, "Roll on behalf of Pascal Thubert (pthubert)" <roll-
    > bounces@ietf.org on behalf of pthubert@cisco.com> wrote:
    > 
    >             Hello Li
    > 
    >             My initial thought was that we'd not use AOO at all in DAO messages,
    > we'd  elide all options or no option.
    >             I do not really see how we could do partial increments of some options
    > and not others.
    >             I see that your proposal requires AOOs in DAOs as well. Do you have a
    > case in mind?
    >             If we start replacing stuff with AOO tin DAOs things could get hairy, like I
    > have 2 targets with a few transit each. One target changes. Or one transit
    > changes. How would we use the AOO?
    > 
    >             The keep it simple way is to add a section on DAO that does not use AOO
    > at all.
    > 
    >             Take care,
    > 
    >             Pascal
    > 
    >             -----Original Message-----
    >             From: Roll <roll-bounces@ietf.org> On Behalf Of Li Zhao (liz3)
    >             Sent: mardi 22 octobre 2019 16:36
    >             To: Routing Over Low power and Lossy networks <roll@ietf.org>
    >             Subject: Re: [Roll] FW: New Version Notification for draft-thubert-roll-
    > eliding-dio-information-01.txt
    > 
    >             Hello Again Pascal,
    > 
    >             I've written it down but it seems that I don't have permission to push it to
    > github.
    >             The main change is in section 4.3 as following:
    > 
    >             The abbreviated version of an option is a replacement for any option.
    >                It does not advertise the content of the option but indicates the
    >                sender's value for the last modified sequence of that option. It
    >                is transported in a 4-bytes long Abbreviated Option Option (AOO).
    >                AOO MAY be present in DIO and DAO messages as follows:
    > 
    >                  0                   1                   2                   3
    >                  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
    >                  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    >                  |  Option Type  | Option Length | Abbrev. opt.  | Last Mod Seq. |
    >                  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    > 
    >                              Figure 3: Abbreviated Option Option Format
    > 
    >                Option fields:
    > 
    >                Option Type
    >                   One byte indicating "Abbreviated Option", see Table 2 in
    >                   Section 8.2
    > 
    >                Option Length
    >                   MUST be set to 2 indicating Option data of 2 bytes
    > 
    >                Abbreviated Option
    >                   The Option Type of the option being abbreviated
    > 
    >                Last Modification Sequence
    >                   The last modified RCSS when carried in DIO or the last modified
    >                   DAOSequence when carried in DAO
    > 
    >                When a node receives a DAO-ACK for a given DAO sequence, then if the
    >                next DAO has the unchanged options, the node MAY reuse the
    > DAOsequence
    >                and elide all options with AOO. Abbreviated Option SHOULD be ignored.
    >                The Last Modification Sequence is the last DAOsequence. The next DAO
    >                MAY also unset ‘K’ flag to not expect a DAO-ACK, if node can assume
    >                the risk that the DAO is lost and the state times out at the DAO
    >                receiver. It is RECOMMENDED in non-storing mode because DAO always
    > has
    >                the same content.
    > 
    > 
    >             Best regards,
    >             Li
    > 
    >             On 2019/10/22, 19:27, "Roll on behalf of Li Zhao (liz3)" <roll-
    > bounces@ietf.org on behalf of liz3@cisco.com> wrote:
    > 
    >                 Hello Pascal,
    > 
    >                 Agree with you.
    >                 We can use AOO with last Modification DAO sequence to elide all
    > options in DAO. In this case, we can ignore the Abbreviated Option field or set it
    > to 0xFF. Which do you prefer?
    > 
    >                 For the DAO lost case, even in normal DAO case, node has the risk of
    > lost DAO message. Node should set 'K' flag according to different network
    > environment.
    >                 It should also work in DAO-AOO case. Admin can balance the risk of lost
    > DAO message and 4-bytes DAO-ACK load.
    > 
    > 
    >                 Best regards,
    >                 Li
    > 
    >                 On 2019/10/22, 16:53, "Roll on behalf of Pascal Thubert (pthubert)"
    > <roll-bounces@ietf.org on behalf of pthubert@cisco.com> wrote:
    > 
    >                     Hello Again Li:
    > 
    >                     I looked at it and an simple step could be that when a node receives a
    > DAO-ACK for a given DAO sequence, then if the next DAO has the same content
    > the node may reuse the DAO sequence and elide the options. It may also decide
    > not refrain from asking an ack, at the risk that the DAO is lost and the state times
    > out at the DAO receiver.
    > 
    >                     All the best;
    > 
    >                     Pascal
    > 
    >                     -----Original Message-----
    >                     From: Roll <roll-bounces@ietf.org> On Behalf Of Pascal Thubert
    > (pthubert)
    >                     Sent: mardi 22 octobre 2019 07:58
    >                     To: Routing Over Low power and Lossy networks <roll@ietf.org>
    >                     Subject: Re: [Roll] FW: New Version Notification for draft-thubert-
    > roll-eliding-dio-information-01.txt
    > 
    >                     Hello Li
    > 
    >                     Would be great!
    > 
    >                     The xml is available on github under roll-wg.
    >                     My expectation is that the source of the non storing DAO increases a
    > sequence nb when there is a change and abbreviates it when there is none.
    > 
    >                     You need to think of what happens when the updated DAO is lost, eg
    > MUST an ack or something and only abbreviate after a positive DAO ACK...
    > 
    >                     Regards,
    > 
    >                     Pascal
    > 
    >                     > Le 22 oct. 2019 à 04:29, Li Zhao (liz3) <liz3@cisco.com> a écrit :
    >                     >
    >                     > 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)" <roll-bounces@ietf.org on behalf of pthubert@cisco.com> 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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