Re: [Roll-bier-dt] roll-bier-dt

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Fri, 19 October 2018 14:54 UTC

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From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: Toerless Eckert <tte@cs.fau.de>
CC: Carsten Bormann <cabo@tzi.org>, "roll-bier-dt@ietf.org" <roll-bier-dt@ietf.org>
Thread-Topic: [Roll-bier-dt] roll-bier-dt
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Subject: Re: [Roll-bier-dt] roll-bier-dt
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Please consider this then :)

https://datatracker.ietf.org/doc/draft-thubert-6lo-bier-dispatch/

take care,

Pascal

> -----Original Message-----
> From: Toerless Eckert <tte@cs.fau.de>
> Sent: vendredi 19 octobre 2018 15:52
> To: Pascal Thubert (pthubert) <pthubert@cisco.com>
> Cc: Carsten Bormann <cabo@tzi.org>; roll-bier-dt@ietf.org
> Subject: Re: [Roll-bier-dt] roll-bier-dt
> 
> On Fri, Oct 19, 2018 at 01:20:11PM +0000, Pascal Thubert (pthubert) wrote:
> > Sure, but the mystery to me is what goes transported with BIER.
> 
> As said, BIER proper can encapsulate anything deemed important enough to get
> a code point in the BIER encap. I am saying "proper" because ROLL may not
> want to take RFC8296 given the likely competition with 6LowPan.
> 
> > Because that is the heart of the problem we are facing in this DT.
> > If BIER transports a same IP packet to multiple destinations, then they must all
> accept the same packet.
> 
> More a property of the larger clas of multicasting overall assuming tojust copy
> the payload - and not to modify it.
> 
> I thought we had killed in last weeks meeting the idea of trying to come up with
> a mechanism that manages to use packet replication (BIER) and then modding
> received copies to fake different per-receiver IP unicast packets
> - because of the problem of making this architecturally work well with higher
> layers like UDP that also have a notion of an IP (pseudo) header.
> Too much faking needed. At least thats what i tried to summarize in my slides.
> 
> Aka: We use BIER-TE for unicast packets but then the expectation is that there is
> just one destination, and the whole purpose of BIER-TE is not replication but
> source routing. And we use BIER-TE(/BIER) for IP multicast packets where there
> can be 1 or more destinations.
> 
> [ Of course there are fun extensions later, e.g.: a unicast packet could  still be
> sent to redundant nodes sharing an IP adddress and therefore  able to
> receive/process the same packet, but i think thats less likely  something one
> would do in a ROLL domain. ]
> 
> > Moreover, if the destination is not the router indicated by the bit
> > but a neighbor or a set of neighbors to that router, then the inner
> > packet must indicate that.
> > All in all, that tells me that the transported packet is IP multicast.
> 
> Yes, we have two layers. The BIER layer that only reaches nodes with an
> assigned BIER bit, and they can communicate potentially any payload across
> BIER, IP or other. And then on top of that there is IP multicast between the BIER
> edge nodes and IP unicast/multicast only nodes. The pictures in the slide deck
> posted intend to show that (that IP multicast building block picture still TBD).
> 
> > What do I miss?
> 
> I think primarily me wanting to figure out the encap we use within the BIER-
> ROLL domain: RFC8296 vs. 6LowPan+extensions.
> 
> Cheers
>     Toerless
> 
> > Take care,
> >
> > Pascal
> >
> > > -----Original Message-----
> > > From: Toerless Eckert <tte@cs.fau.de>
> > > Sent: vendredi 19 octobre 2018 15:14
> > > To: Pascal Thubert (pthubert) <pthubert@cisco.com>
> > > Cc: Carsten Bormann <cabo@tzi.org>; roll-bier-dt@ietf.org
> > > Subject: Re: [Roll-bier-dt] roll-bier-dt
> > >
> > > On Fri, Oct 19, 2018 at 12:36:06PM +0000, Pascal Thubert (pthubert)
> wrote:
> > > > Hello Toerless:
> > > >
> > > > Well, there is as Carsten says a multicast support for RPL storing
> > > > mode, but not
> > > for non-storing. This is where Carsten's draft comes in to play.
> > >
> > > Sure. As said, i may not have correctly captured what Mcr was
> > > explaining,
> > >
> > > > In normal BIER, the bits indicate the routers, don't they? So
> > > > there's an IP
> > > packet inside, correct, like in my tunnel mode? But then I expect it
> > > is the same packet for all destinations. So how does htat work, is
> > > it a mcast packet or do all the destination have a same IP address?
> > >
> > > "Proper BIER" (TM) (the stuff done by BIER-WG) has defined its own
> > > encapsulation header (RFC8296) that sits on top of MPLS or ethernet
> > > and that has its own next-proto field/registry, so it can be
> > > followed by IP or anything else that BIER-WG feels deserves a code point in
> that registry.
> > >
> > > Cheers
> > >     Toerless
> > >
> > > > Pascal
> > > >
> > > > > -----Original Message-----
> > > > > From: Roll-bier-dt <roll-bier-dt-bounces@ietf.org> On Behalf Of
> > > > > Toerless Eckert
> > > > > Sent: vendredi 19 octobre 2018 14:21
> > > > > To: Carsten Bormann <cabo@tzi.org>
> > > > > Cc: roll-bier-dt@ietf.org
> > > > > Subject: Re: [Roll-bier-dt] roll-bier-dt
> > > > >
> > > > > That was me taking notes what Michael said, and maybe i didn't
> > > > > transcribe it correctly. Hope Michael is subscribed here to answer.
> > > > >
> > > > > I think i was more wondering about the suport of compressed IP
> > > > > multicast headders in 6LowPan because that is unclear to me and
> > > > > we probably need to take one of the DT meetings to detail more
> > > > > what extensions we need to do for 6LowPan to support BIER.
> > > > >
> > > > > Cheers
> > > > >     Toerless
> > > > >
> > > > > On Fri, Oct 19, 2018 at 07:45:50AM +0200, Carsten Bormann wrote:
> > > > > > On Oct 19, 2018, at 04:56, Toerless Eckert <tte@cs.fau.de> wrote:
> > > > > > >
> > > > > > > https://raw.githubusercontent.com/toerless/roll-bier/master/
> > > > > > > note
> > > > > > > s/18
> > > > > > > 1017-roll-bier-notes.txt
> > > > > >
> > > > > > What do you mean with ???RPL does not support multicast.????
> MOP=3?
> > > > > > (That is of course storing mode only, and storing mode
> > > > > > doesn???t exist :-), so
> > > > > you have a point.
> > > > > > That???s why we did ccast, to fill in multicast for
> > > > > > non-storing
> > > > > > mode.)
> > > > > >
> > > > > > Grüße, Carsten
> > > > >
> > > > > --
> > > > > ---
> > > > > tte@cs.fau.de
> > > > >
> > > > > _______________________________________________
> > > > > Roll-bier-dt mailing list
> > > > > Roll-bier-dt@ietf.org
> > > > > https://www.ietf.org/mailman/listinfo/roll-bier-dt
> > >
> > > --
> > > ---
> > > tte@cs.fau.de
> >
> > _______________________________________________
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> > https://www.ietf.org/mailman/listinfo/roll-bier-dt
> 
> --
> ---
> tte@cs.fau.de