Re: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf" flag in ARO]

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Fri, 22 April 2011 06:50 UTC

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Date: Fri, 22 Apr 2011 08:49:53 +0200
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Thread-Topic: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf" flag in ARO]
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From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: "Geoff Mulligan" <geoff@proto6.com>
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Subject: Re: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf" flag in ARO]
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Geoff:

My sense is that we failed to meet a quorum to work efficiently on the backbone router. After the split, it was always a few hands both ways.
Nevertheless, this group worked on the problem for over a year after Dublin, and the design was pretty clear. 
The TID was required to distribute the LBRs.

This thread is not about the backbone router draft. Here, we are talking about the TID in the ND options. 

Scaling to thousands is a requirement in a number of environments I'm dealing with, in particular industrial.
So I'm asking you and the group which plan B we have to scale if there is no TID. I've not seen any so far.
If there's none then yes, we're hitting a wall. That's problem 1.

In any fashion, I've not seen how the current ND  draft operates if control packets are lost or out of order (eg mesh under).
For all I've seen, the host cannot be sure of the final state in the router because the ack is not correlated with the req.
That's problem 2.

Finally, a TID in the control also helps protect the protocol against replay attacks. Any MIC is enough.

I'd like to see a real sense of the group whether we want the TID in or not. Guys, please?

Pascal
http://www.xtranormal.com/watch/7011357/

> -----Original Message-----
> From: Geoff Mulligan [mailto:geoff@proto6.com]
> Sent: Thursday, April 21, 2011 9:42 PM
> To: Pascal Thubert (pthubert)
> Cc: Erik Nordmark; nicolas.riou@schneider-electric.com; 6lowpan@ietf.org
> Subject: RE: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf" flag in
> ARO]
> 
> Pascal,
>   I couple of people supporting the TID is not group consensus.  We have had
> many presentations and discussions about multiple LBRs, backbone LBRs and
> more and none have met with the support of the working group.
> 
> In your opinions we are crashing, but I fail to see that this is the opinion of
> the working group.
> 
> If there are other in the working group that strongly advocate this TID idea or
> the work on multiple and backbone LBRs then they need to speak up now en
> masse or we must move on.
> 
> 	geoff
> 
> 
> On Thu, 2011-04-21 at 21:32 +0200, Pascal Thubert (pthubert) wrote:
> > Geoff:
> >
> > There is twice as much support for restoring the TID than there is for  not
> doing it.
> > Before we drop the TID, I'd like to see a proposal that allows a 6LoWPAN
> ND subnet to scale with multiple LBRs, allows nodes to move from a router to
> the next, and that does not need a TID.
> > Otherwise, we are not speeding towards the wall, we're already crashing.
> >
> > Pascal
> > http://www.xtranormal.com/watch/7011357/
> >
> > > -----Original Message-----
> > > From: Geoff Mulligan [mailto:geoff.ietf@mulligan.com]
> > > Sent: Thursday, April 21, 2011 5:41 PM
> > > To: Pascal Thubert (pthubert)
> > > Cc: Erik Nordmark; nicolas.riou@schneider-electric.com;
> > > 6lowpan@ietf.org
> > > Subject: Re: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf"
> > > flag in ARO]
> > >
> > > Pascal,
> > >   We need to close on this discussion.
> > >
> > > Back in Hiroshima the Working Group decided that Backbone router
> > > stuff and "address defense" across backbone routers was not going to
> > > be part of ND draft.  It appeared that the draft was getting way to
> > > complicated and the Working Group decided to simplify things.
> > >
> > > I have not seen much support on the list for making these changes to
> > > include the TID in ND.
> > >
> > > We need to get this draft completed.  If there is a large "unheard from"
> > > support group for these changes, please speak up or we shall move
> > > forward with the draft as it is.
> > >
> > > 	geoff
> > >
> > >
> > >
> > >
> > > On Thu, 2011-04-21 at 09:27 +0200, Pascal Thubert (pthubert) wrote:
> > > > Hi Erik
> > > >
> > > > The TID is not a strong coupling between the H2R and the R2R
> > > > operations,
> > > and it is not a coupling with a RPL version  explicitly.
> > > > It is an abstract information that if defined properly can be used
> > > > by many
> > > forms or R2R interactions.
> > > > As demonstrated by older versions of the ND spec (Backbone
> > > > Router), RPL,
> > > and MIP.
> > > >
> > > > 6LoWPAN ND cannot scale if the node needs to register to all LBRs.
> > > 6LoWPAN ND does not define anymore any LBR interaction.
> > > > IOW, 6LoPWAN ND lost the capability to scale when the backbone
> > > > router
> > > piece was removed from the draft.
> > > > Which means that it lost its capability to apply in the domains
> > > > I'm looking at
> > > (industrial and metering).
> > > >
> > > > With the TID, we know that we can restore scalability in the
> > > > future, and we
> > > know how. I do not know of a plan B.
> > > >
> > > > Pascal
> > > > http://www.xtranormal.com/watch/7011357/
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Erik Nordmark [mailto:nordmark@acm.org]
> > > > > Sent: Thursday, April 21, 2011 1:25 AM
> > > > > To: nicolas.riou@schneider-electric.com
> > > > > Cc: Pascal Thubert (pthubert); 6lowpan@ietf.org; Dijk, Esko
> > > > > Subject: Re: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf"
> > > > > flag in ARO]
> > > > >
> > > > > On 4/20/11 1:21 AM, nicolas.riou@schneider-electric.com wrote:
> > > > > >
> > > > > > Dear Pascal and al,
> > > > > >
> > > > > > I support the idea of reviving the TID in ARO and DAR/DAC.
> > > > > > Supporting a TID directly in the node initiating the initial
> > > > > > NS appears much simpler than time stamping in the parent router.
> > > > >
> > > > > How would you make this work if the protocol between the routers
> > > > > is not RPLv1, but some future version of RPL or a completely
> > > > > different routing protocol?
> > > > >
> > > > > The decoupling of the host-router interaction from router-router
> > > > > interaction has served us well in the history of the Internet.
> > > > >
> > > > >       Erik
> > > > >
> > > > > > A simple and efficient method to detect mobility of hosts
> > > > > > along a backbone of Edge Routers is an important feature to
> > > > > > deploy backbones of Edge Routers in Buildings and should be
> > > > > > clarified before closing 6LoWPAN WG.
> > > > > >
> > > > > > Cheers,
> > > > > > Nicolas
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > *"Pascal Thubert (pthubert)" <pthubert@cisco.com>* Envoyé par :
> > > > > > 6lowpan-bounces@ietf.org
> > > > > >
> > > > > > 18/04/2011 10:37
> > > > > >
> > > > > >
> > > > > > A
> > > > > > 	"Dijk, Esko" <esko.dijk@philips.com>, "Erik Nordmark"
> > > > > > <nordmark@acm.org> cc
> > > > > > 	6lowpan@ietf.org
> > > > > > Objet
> > > > > > 	Re: [6lowpan] FW: TID in ARO [was: "Advertize on Behalf"
> flag
> > > > > > in
> > > > > ARO]
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > Hi Esko, Erik
> > > > > >
> > > > > > The discussion on RPL and hosts should happen on the RPL list
> > > > > > under a different topic. The point being discussed here is this:
> > > > > >
> > > > > > The reality is also that those (LLN) networks will need to
> > > > > > scale to large subnets in plants, building, etc... (see the
> > > > > > requirement drafts in ROLL). Registering to all LBRS is totally
> impractical.
> > > > > > 6LoWPAN ND requires a coordination between LBRs but does not
> > > > > > say
> > > how it happens.
> > > > > > This problem was discussed in 6LoWPAN; the answer was in
> > > > > > ND-01to07; and it requires a TID, for the same reason as RPL.
> > > > > > Removing the backbone operation and the TID from the draft is
> > > > > > ostrich
> > > policy.
> > > > > >
> > > > > > BTW 6LoWPAN ND needs a TID to correlate the NS and the NA as
> > > > > > all other registrations do when strict ordering is not
> > > > > > guaranteed (MIP being an example). Say that due to some
> > > > > > config, a node registers a lifetime of X, then deregisters
> > > > > > (lifetime 0), then reregisters (lifetime X) in a rapid sequence, but
> does not get an answer yet.
> > > > > > Then it finally gets 2 AROs back, lifetime X and 0. What's the
> > > > > > final state
> > > in the router?
> > > > > >
> > > > > > I'd like to hear what others think.
> > > > > >
> > > > > > Pascal
> > > > > > http://www.xtranormal.com/watch/7011357/
> > > > > >
> > > > > >
> > > > > >  > -----Original Message-----
> > > > > >  > From: Dijk, Esko [mailto:esko.dijk@philips.com]  > Sent:
> > > > > > Monday, April 18, 2011 10:19 AM  > To: Erik Nordmark; Pascal
> > > > > > Thubert
> > > > > > (pthubert)  > Cc: 6lowpan@ietf.org  > Subject: RE: [6lowpan] FW:
> > > > > > TID in ARO [was: "Advertize on Behalf" flag in  > ARO]  >  >
> > > > > > Hello Erik,
> > > > > > >  > taking the definition you quoted:
> > > > > >  > 'host' refers to an LLN device that can generate but does
> > > > > > not forward  > RPL traffic  >  > the question may arise what
> > > > > > is "RPL traffic"? It is not defined in the RPL draft  > it
> > > > > > seems. Pascal clarified to me it is traffic associated to a
> > > > > > RPL instance, not  > necessarily RPL protocol messages. This
> > > > > > means that a host could generate  > RPL traffic without being
> > > > > > aware of the existence of RPL at all. So, _not_ all  > hosts have to
> speak RPL?
> > > > > >  > The RPL draft does not explicitly state if "hosts" in a RPL
> > > > > > network always  > speak RPL, never speak RPL, or can be mixed
> > > > > > RPL/non-RPL speakers.
> > > > > >  >
> > > > > >  > Taking the definition of 'node' in the RPL draft:
> > > > > >  > 'node' refers to any RPL device, either a host or a router
> > > > > > >
> > > > > > > rules out (?) the option that all "hosts" are non-RPL
> > > > > > > speakers,
> > > > > > since there  > may be a "RPL device" (i.e. RPL-speaking
> > > > > > device, I
> > > > > > assume) that is also a host.
> > > > > >  >
> > > > > >  > I communicated these perceived unclarities to Pascal and
> > > > > > the RFC editor 2  > weeks ago. Once this is clear I think the
> > > > > > present discussion can continue.
> > > > > >  > And then there is the related discussion of ND support for
> > > > > > sleepy devices,  > the original topic of Anders ;)  >  > best
> > > > > > regards,  >  > Esko  >  >  >  > -----Original Message-----  > From:
> > > > > > 6lowpan-bounces@ietf.org [mailto:6lowpan-bounces@ietf.org] On
> > > > > > > Behalf Of Erik Nordmark  > Sent: Friday 15 April 2011 18:39  > To:
> > > > > > Pascal Thubert (pthubert)  > Cc: 6lowpan@ietf.org  > Subject: Re:
> > > > > > [6lowpan] FW: TID in ARO [was: "Advertize on Behalf" flag in
> > > > > > > ARO]
> > > > > > >  > On 4/14/11 11:43 PM, Pascal Thubert (pthubert) wrote:
> > > > > >  >
> > > > > >  > > RPL can do what all classical IGPs can do WRT hosts. That
> > > > > > is as long  > > as the host address belongs to the router's
> > > > > > prefix and stays attached  > > to that router.
> > > > > >  >
> > > > > >  > I just realized that we might be talking about a different
> > > > > > definition of "host".
> > > > > >  > What I mean by "host" is a node which does not participate
> > > > > > in a routing  > protocol, and does not forward packets (except
> > > > > > packets explicitly addressed  > to itself using e.g., a routing header).
> > > > > >  >
> > > > > >  > However, RPL has a different definition:
> > > > > >  > 'host' refers to an LLN device that can generate but does
> > > > > > not forward  > RPL traffic  >  > Basically per the RPL
> > > > > > definition there is no such thing as a node which does  > not
> > > > > > participate in the RPL protocol.
> > > > > >  > IMHO what is in RPL should have been defined as a
> > > > > > non-forwarding node, so  > that we can have a sane discussion
> > > > > > without getting entangled in terminology  > issues.
> > > > > >  >
> > > > > >  > Which definition of "host" are you using above?
> > > > > >  >
> > > > > >  > Per the RPL definition there is no need for 6lowpan-nd,
> > > > > > since all nodes will  > speak RPL. This is rather confusing, don't you
> think?
> > > > > >  >
> > > > > >  > Erik
> > > > > >  >
> > > > > >  > > When the topology becomes multilink subnet and mobility
> > > > > > is required  > > then it is a new problem entirely, and NO,
> > > > > > 4861 is not a suitable  > > interaction with the router to
> > > > > > allow the router to redistribute a host route.
> > > > > >  > > Because the neighbor cache that 4861 builds is not a of
> > > > > > the same
> > > > > > > > nature as the binding table that 6LoWPAN ND builds.
> > > > > > > > Another thing
> > > > > > that  > > 6LoWPAN ND fails to express correctly. I proposed
> > > > > > text to explain that  > > (attached) but it was not
> > > > > > considered, contributing to the illusion  > > that a cache is a table.
> > > > > >  > >
> > > > > >  > > The reality is also that those networks will need to
> > > > > > scale to large  > > subnets in plants, building, etc... (see
> > > > > > the requirement drafts in  > > ROLL). Registering to all LBRS
> > > > > > is totally
> > > impractical.
> > > > > > 6LoWPAN ND  > > requires a coordination between LBRs but does
> > > > > > not say how it happens.
> > > > > >  > > This problem was discussed in 6LoWPAN; the answer was in
> > > > > > ND-01to07;  > > and it requires a TID, for the same reason as RPL.
> > > > > > Removing the  > > backbone operation and the TID from the
> > > > > > draft is ostrich
> > > > > policy.
> > > > > >  > >
> > > > > >  > > RPL already adapted to the new reality of large multilink
> > > > > > subnet with  > > inner mobility. Placing the blame on RPL is
> > > > > > another illusionist trick.
> > > > > >  > > And this is not RPL last call.
> > > > > >  > >
> > > > > >  > > BTW 6LoWPAN ND needs a TID to correlate the NS and the NA
> > > > > > as all other  > > registrations do when strict ordering is not
> > > > > > guaranteed (MIP being an  > > example). Say that due to some
> > > > > > config, a node registers a lifetime of  > > X, then
> > > > > > deregisters (lifetime 0), then reregisters (lifetime X) in a
> > > > > > > > rapid sequence, but does not get an answer yet. Then it
> > > > > > finally gets
> > > > > > 2
> > > > > >  > > AROs back, lifetime X and 0. What's the final state in the router?
> > > > > >  > >
> > > > > >  > > It seems we can never agree on any of this. I'd like to
> > > > > > hear what
> > > > > > > > others think.
> > > > > >  > >
> > > > > >  > > Pascal
> > > > > >  > > http://www.xtranormal.com/watch/7011357/
> > > > > >  > >
> > > > > >  > >
> > > > > >  > >> -----Original Message-----  > >> From:
> > > > > > 6lowpan-bounces@ietf.org [mailto:6lowpan-
> > > > > bounces@ietf.org]
> > > > > > On  > >> Behalf Of Erik Nordmark  > >> Sent: Friday, April 15,
> > > > > > 2011
> > > > > > 1:30 AM  > >> To: 6lo>> '6lowpan'
> > > > > >  > >> Subject: Re: [6lowpan] Fwd: Re: "Advertize on Behalf"
> > > > > > flag in ARO  > >>  > >>  > >> On 4/13/11 12:53 AM, Pascal
> > > > > > Thubert
> > > > > > (pthubert)
> > > > > > wrote:
> > > > > >  > >>> Hi Erik:
> > > > > >  > >>>
> > > > > >  > >>> The RPL (DAO) sequence number allows the node to
> > > > > > increment rapidly  > >>> in case of rapid changes and then
> > > > > > lazily when the situation is  > >>> stable and DAO are scarce.
> > > > > > The increase is strictly monotonous which  > >  > >>> is critical to us.
> > > > > >  > >>>
> > > > > >  > >>> A time stamp imposes a synchronization between the
> routers.
> > > > > > We do  > >>> not have such mechanism in RPL. A time unit (a
> > > > > > granularity) must be  > >>> agreed upon. Within that unit,
> > > > > > movements go undetected so the time  > >>> unit must be thin
> > > > > > grained
> > > to cover rapid changes.
> > > > > > Yet, depending on  > >>> the medium, the time unit, and the
> > > > > > size of the network, it is not  > >>> necessarily
> > > > > > easy/possible to guarantee a strictly monotonous value  > >>>
> > > > > > with a thin grained time unit. And we have limited space (2
> > > > > > octets)
> > > > > >  > >>> and have to deal with wrap around, which divides the
> > > > > > space by at  > > least 3.
> > > > > >  > >>>
> > > > > >  > >>> So RPL went for a sequence number.
> > > > > >  > >>
> > > > > >  > >> But the unstated assumption that RPL made is that all
> > > > > > host-to-router  > >> protocols have to now be RPL aware. That
> > > > > > doesn't sound like good  > > design.
> > > > > >  > >> A host isn't aware of whether the routers speak IS-IS or
> > > > > > OSPF, so why  > >> do the hosts need to be aware of RPL by
> > > > > > passing some TID around?
> > > > > >  > >>
> > > > > >  > >>> I think ND has the same need as MIP for a TID == Sequence #
> .
> > > > > > We  > >>> know of MIP; We know of RPL. We know of the
> backbone
> > > > > > router
> > > > > > > >>> operation. We know we'll need the TID and we know
> > > > > > > >>> exactly why. I think we should have it in the 6LowPAN ND
> > > > > > > >>> spec right away to
> > > > > > avoid  > >>> interop issues when we add RPL and BR operations.
> > > > > >  > >>
> > > > > >  > >> I don't see a need in 6lowpan-nd for a TID; the protocol
> > > > > > works fine  > > without it.
> > > > > >  > >> I think RPL needs to be improved to deal with reality.
> > > > > > Isn't there a  > >> desire for RPL to handle 4861 hosts? Those
> > > > > > would never know about a  > > TID.
> > > > > >  > >>
> > > > > >  > >> Erik
> > > > > >  > >>
> > > > > >  > >> _______________________________________________
> > > > > >  > >> 6lowpan mailing list
> > > > > >  > >> 6lowpan@ietf.org
> > > > > >  > >> https://www.ietf.org/mailman/listinfo/6lowpan
> > > > > >  > > _______________________________________________
> > > > > >  > > 6lowpan mailing list
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> > > > > >  > >
> > > > > >  >
> > > > > >  > _______________________________________________
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