Re: [Roll] Erik Kline's Discuss on draft-ietf-roll-useofrplinfo-42: (with DISCUSS and COMMENT)

[Erik Kline <[e-mail]>]

On Wed, Dec 16, 2020 at 10:01 AM Michael Richardson <[e-mail]>
wrote:

>
> Erik Kline via Datatracker <[e-mail]> wrote:
>     >   I might recommend instead referring to RFC 6554 S4.2 for how to
>     > handle RH3's if the node is also a RPL-aware router and say it MUST
>     > drop the packet if segments left is non-zero and it's not a RPL-aware
>     > router.
>
>     >   Related: I'd also recommend:
>
>     >   "It should just be noted that an incoming RH3 must be fully
> consumed,
>     > or very carefully inspected."
>
>     ->
>
>     >   "It should just be noted that an incoming RH3 MUST be fully
>     > consumed."
>
> I think that Pascal and I, when we write the "carefully inspected", is
> that we are imagining situations where the topology is a bit subtle.
> Perhaps there are firewalls involved.
> Perhaps a device has multiple interfaces (many radios for instance) and the
> extra segments address the other interfaces.
>
> Also draft-ietf-anima-autonomic-control-plane uses storing mode, so never
> has
> RH3 headers, but imagine if it did.
>
> One could have a situation where the physical system containing one or more
> layers of container was not the ultimate last hop from a logical point of
> view.  Rather than inner container was.  So, it's all the same stack
> actually.  In that case, an optimization might be to process more than
> one segment in that stack.
> (The ANIMA ACP definitely supports having VMs and containers inside
> routers)
>

(trying to respond to both threads)

I guess, one way to look at it would be: for any given node, receiving a
packet with an RH3 and segments left > 0, does the discussion here change
anything?  If the node is part of nested layers of networking it might do
what it's configured to do, and if it's a plain vanilla host it should
reject the packet.

If there's no behaviour change then perhaps we can just trim all the text
and point text elsewhre (I have a note from reading last night about
roll-unaware-leaves S5.4 being a possible landing spot for a pointer, as
Pascal mentioned above).

Thanks for the ongoing discussion!

So, I can live with your suggestion, because in my case above,
> we can argue that it's still "consumed"
>
>     > * I'm confused by the use of "consumed" here.  Is the final RH3 entry
>     > RUL's address?  I guess you could say RH penultimate hop "consumes"
> the
>     > header because the ultimate destination address is put in the header
> DA
>     > field.  Seems a bit odd though.
>
> Yes, that's what we mean.
> Once that ultimate destination is in the DA, then the RH3 is a dummy, but
> one
> we are aren't supposed to remove.
>
>     >   I assume 6LR_n gets RUL's address from the last segment in RH3.
>
>     >   "Consumed" means segments left == 0, I guess?  I suppose should
> have
>     > picked up on this terminology when it was first used in Section 2.
>     > Maybe clarify what it means in that section (2)?
>
> Yes.
>
>
> --
> Michael Richardson <[e-mail]>   . o O ( IPv6 IøT consulting )
>            Sandelman Software Works Inc, Ottawa and Worldwide
>
>
>
>
>