Subject: [Roll] Nodes Mobility Support in RPL

From: Leila Ben Saad <[email-masked]>
Date: Wed, 06 Jan 2010 15:52:54 +0100

Dear WG,

Is RPL able to support the mobility of DAG roots ? Because if we move  
DAG roots frequently, the topology will be modified, new DODAGS must  
be constructed, more DIO messages will be sent which can can diminish  
the energy of nodes and limit their lifetime.

Has RPL been already evaluated in network with mobile nodes ?

Thanks,

Leila Ben Saad
PhD Student
ENS Lyon France

---

From: Emmanuel Baccelli <[email-masked]>
Date: Wed, 6 Jan 2010 16:10:42 +0100

Hi Leila,

basically RPL targets sensor where nodes basically do not move relatively to
one another. So in that sense, the answer to your question is: not really ;)

cheers,

Emmanuel

On Wed, Jan 6, 2010 at 3:52 PM, Leila Ben Saad
<[email-masked]>wrote:

> Dear WG,
>
> Is RPL able to support the mobility of DAG roots ? Because if we move DAG
> roots frequently, the topology will be modified, new DODAGS must be
> constructed, more DIO messages will be sent which can can diminish the
> energy of nodes and limit their lifetime.
>
> _______________________________________________
> Roll mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/roll
>

---

From: Michael Richardson <[email-masked]>
Date: Wed, 06 Jan 2010 10:49:18 -0500

At some point it was suggested that there would be subsystems of
multiple nodes where one node would run RPL, and the others nodes
would be tethered in some way to that node.
(For instance, a residential house participating in a neighbourhood
DAG, where the systems inside the house are wired.  Or all the actuators
and sensors components on a large machine...)

That is, not every system in a DAG needed to run RPL, as long as they
had good connectivity to one that did. 

I was thinking about this the other day, and forgot about the wired part
of this initially, and was thinking about a situation where one node
would run RPL (with a single radio for instance, but multiple antenna), 
such that the other nodes would need to hear RAs from some place, and
need to be given addresses.  

I worried that the RAs from the node would be heard by the other RPL
nodes, and then thought that this might not work.  
Well, it does, if you have a wired interface, or multiple radios and the
RPL node acts as bridge, and the bridge can therefore filter traffic a
bit.  It's not clear to me that this works well if "local" traffic can
leak. 

But, if you have multiple interfaces, you might also do L3 routing
instead.  Do people imagine this?  Is it reasonable to use DHCPv6-PD to
number that interface?  I think that it is not a problem for the DIO to
contain those prefixes...

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]   Michael Richardson, Sandelman Software Works, Ottawa, ON    |net architect[
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---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 13 Jan 2010 15:00:13 +0100

As a pre-requisite, I would consider looking at the RoLL requirements
documents and search for 'mobil' and find some use cases which were used
as motivators for RoLL.  But during the subsequent RoLL work, the
mobility aspects were not hugely important.

Le 06/01/2010 15:52, Leila Ben Saad a écrit :
> Dear WG,
>
> Is RPL able to support the mobility of DAG roots ?

Well I guess DAG roots could move around a little bit and stay within
the link-layer's reachability range (e.g. 10meters).  If this is
considered 'mobility' then automatically RPL does support it I believe.

On another hand, if we consider 'mobility' to involve a change of the
address assigned to a node then I don't think RPL has much support for
it.  I am not sure this is needed either in RPL.

> Because if we move DAG roots frequently, the topology will be
> modified, new DODAGS must be constructed, more DIO messages will be
> sent which can can diminish the energy of nodes and limit their
> lifetime.
>

I don't know.  Do you mean a Mobile Node as in Mobile IPv6?  Or just
entities which could be mobile?  I.e. is a DAG Root a Mobile Node?  Or
are only the nodes within the RoLL network (not the DAG Root) mobile nodes?

Just some comments,

Alex

>
> Thanks,
>
> Leila Ben Saad PhD Student ENS Lyon France
>
>
>
>
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