[Contiki-developers] 6LoWPAN multicast address

[Damien Roth]

Hello,

I'm currently trying to understand the autoconfiguration mechanism of 6LoWPAN. My question is "How the MAC layer understand the All Router multicast address (FF02::2) used by the Router Solicitation messages ?"

According to me, the packet should be broadcasted on the radio medium and only the "routers" should handle it. Stop me if I am wrong.

However, I cannot figure how the packet is sent in a 802.15.4 star topology (or a cluster-tree). Does somebody know how 802.15.4 handles this ?

I tried to analyze how it works in Contiki but I am stuck in the uip_nd6_rs_output function of the uip-nd6.c file. I did not understand when the packet is sent in this function.

Thanks in advance.

-- 
Damien ROTH - PhD student
Strasbourg University, France

[David Kopf]

I think broadcasts like NS/NA/RS/RA only go to nodes within listening
distance. If you want multihop you would need to configure at least one of
those also as a router.
RPL does mesh configuration through node-to-node broadcasts but those are
constructed by each node, not forwarded. After the mesh forms unicast
packets are forwarded using the routing tables.

If you did forward broadcasts I think they would bounce around until
reaching the hop limit, possibly in a geometrically increasing chain
reaction.

-----Original Message-----
From: Damien Roth
Sent: Tuesday, August 09, 2011 4:49 AM
To: contiki-d...@lists.sourceforge.net
Subject: [Contiki-developers] 6LoWPAN multicast address

Hello,

I'm currently trying to understand the autoconfiguration mechanism of
6LoWPAN. My question is "How the MAC layer understand the All Router
multicast address (FF02::2) used by the Router Solicitation messages ?"

According to me, the packet should be broadcasted on the radio medium and
only the "routers" should handle it. Stop me if I am wrong.

However, I cannot figure how the packet is sent in a 802.15.4 star topology
(or a cluster-tree). Does somebody know how 802.15.4 handles this ?

I tried to analyze how it works in Contiki but I am stuck in the
uip_nd6_rs_output function of the uip-nd6.c file. I did not understand when
the packet is sent in this function.

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[Kerry Lynn]

See http://tools.ietf.org/html/draft-hui-6man-trickle-mcast-01
I think this is the main (only?) option being discussed for
multicast forwarding in 6LoWPANs.

-K-

[Michael Richardson]

>>>>> "Damien" == Damien Roth <ro...@clarinet.u-strasbg.fr> writes:
Damien> Hello,

Damien> I'm currently trying to understand the autoconfiguration
Damien> mechanism of 6LoWPAN. My question is "How the MAC layer
Damien> understand the All Router multicast address (FF02::2) used
Damien> by the Router Solicitation messages ?"

6LowPAN usees a whiteboard do replace much of the functionality provided
by RA/ND.

--
] He who is tired of Weird Al is tired of life! | firewalls [
] Michael Richardson, Sandelman Software Works, Ottawa, ON |net architect[
] m...@sandelman.ottawa.on.ca http://www.sandelman.ottawa.on.ca/ |device driver[
Kyoto Plus: watch the video <http://www.youtube.com/watch?v=kzx1ycLXQSE>
then sign the petition.

[Kerry Lynn]

After I create a local Contiki repo:
git clone git://contiki.git.sourceforge.net/gitroot/contiki/contiki

1) How can I git-diff against the origin to see the changes others
have committed since my clone?

2) Can I git-fetch incremental changes to my repo, or do I need
to clone all over again?

Thanks, -K- (git challenged)

[Mariano Alvira]

On Tue, Aug 09, 2011 at 12:34:28PM -0400, Kerry Lynn wrote:
> After I create a local Contiki repo:
> git clone git://contiki.git.sourceforge.net/gitroot/contiki/contiki
>
> 1) How can I git-diff against the origin to see the changes others
> have committed since my clone?

(assuming you have the branch you want to compare checked out)

git fetch origin

this downloads all the objects in the remote repo. Now you know
what they know.

git diff origin/master

so the diffs.

I use 'git lol' a lot which is aliased to:

(in ~/.gitconfig)

[alias]
lol = log --oneline --decorate --graph

also color is nice:

[color]
ui = true

Visualization tools, like gitk, can be useful to see the
history/branches etc...

> 2) Can I git-fetch incremental changes to my repo, or do I need
> to clone all over again?

git fetch will download all the objects. But I'm inferring that what
you want to do is grab some commits and try them out. There are
somethings you can do.

Make a new test branch to work on, from the good-but-old branch (e.g. master):

git checkout -b test good-but-old

Then use git lol, git log, gitk to find interesting commits and apply
them:

git cherry-pick 6355545

Or you could graft your set of changes on to a commit as the new head
with git rebase:

git rebase 63555

I do this if, say, I have some code that I'm working on, but I want
the most recent version of everything else. So you can just

git rebase master

This will rewind the branch to a common point with master,
fast-forward up master, then reapply everything in order. It can be a
great way to avoid a merge.

And you can always merge:

git merge new-thing

-Mar.

[Damien Roth]

Hello,

Thank you four your responses.
I've done some research about the whiteboard and I didn't found where is it specified.

The only information I got is in the changelog section of Neighbor Discovery draft.
It is written that Whiteboard related sections are removed.
Is there another (valid) document where the Whiteboard is specified ?

Thank you in advance

--
Damien ROTH - PhD student
Strasbourg University, France