[Olsr-dev] OLSR on OLPC?

Hannes Gredler (spam-protected)
Wed Jun 4 20:21:16 CEST 2008

hi scott,

see comments inline:

C. Scott Ananian wrote:
> The OLPC XO-1 has really nice and spiffy 802.11s hardware.
> Unfortunately, we're having some difficulty actually making it scale
> properly in dense or high-traffic scenarios.  I'm interested in:
>  a) consulting with you folks, who seem to have actual real-world
> experience deploying large scale mesh networks,
>  b) actually deploying olsrd as a fall-back mechanism on the XO --
> giving up the power benefits of running 802.11s autonomously in the
> wireless chip in exchange for perhaps better behavior in some
> scenarios,
>  c) finding out how well you are scaling these days: multiple hundreds of nodes?
>  d) discovering your experience with OLSR in dense networks: if I put
> 100 machines in a single room running olsrd, does the network break
> down due to discovery traffic?

most likely, since all the hello timers run at fixed intervals.
most of our municipal networks have a sparse neighborhood,
with typical a handful of nodes in the 1hop neighborhood.

it should not be too difficult to progressively decrease the
hello(and dead) timers if the neighborhood per interface
grows beyond lets say 10 nodes.

>  e) do you separate data and control traffic?  If not, do you have
> problems with interference causing routing instabilities under high
> traffic conditions?

yes we do. transit traffic is all handled within the kernel
(except the BMF plugin which handles multicast in a seperate thread).

>   f) your thoughts on the OLSR extensions to the 802.11s standard: are
> they worth implementing, or did you need to tweak the standard OLSR
> protocol to make it work in real life?

any wireless mesh protocol, without the ability to convey a loss or
usable bandwidth metric is hopelessly broken.

>  g) the media access protocol in standard 802.11 doesn't seem to scale
> much past 30-or-so nodes wanting to talk at the same time.  Have you
> run into this problem in dense deployments?

i'll defer that question to the berlin guys. they have real-world experience
from running olsrd at conventions like the CCC.

>  h) there's some talk on the wiki about a new v2 rfc for olsr -- is
> there some place I could look at the work in progress?  what
> particular challenges does it aim to tackle?

the original goals we have posted at
we have come quite along way, what is missing is a good tool set
to help diagnose problems and aid troubleshooting.


-proper logging and tracing in olsrd (a configurable logger)
-a command line shell people are used from commercial router OSes.
-build in GUI
-runtime reconfiguration of olsrd

> Y'all seem to be doing great work, and I hope to start trying out
> olsrd on the XO builds, which at the least would give us a way to give
> non-XO-using developers a way to play with some of the mesh networking
> features of our software.

thanks !


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