[olsr-dev] OLSR and consistency

giuseppe de marco (spam-protected)
Thu Feb 22 02:31:26 CET 2007

Thank you for your reply.
I'll answer inline.
Bernd Petrovitsch wrote:
> On Wed, 2007-02-21 at 09:04 +0900, giuseppe de marco wrote:
>> Suppose we want to update the routing module (OLSR) with a modified 
>> version of it, or also
>> we want to change the parameters in all OLSR modules running inside the 
>> nodes of an ad-hoc net.
>> How we can handle it automatically?
> - Deploy the new version
> - update the config files: Changes in most variables are relatively uncritical
>    - one can never rule out the possibility of (short-time) routing loops.
>    The only critical thing is that "LinkQualityLevel" must be either "0" on all
>    or no nodes (and "UseHysteresis" must have also the correct value since these
>    are incompatible).
>   Folks, please correct me if there is something important missing!
> - restart the daemon 
It's not totally true. Even if you use LQ but with different window size 
among nodes, results are very difficult
to predict or at least to understand. We tried in our testbed two simple 
1) all nodes with LQ and window size = 10 and then window size = 20
2) all nodes with LQ but different window size
In 1) all is ok, and in particular with window size =20 throughput goes 
better. In 2) sometimes the network runs, sometimes it doesn't.
Same thing if we change the frequency of HELLO messages.

>> I think OLSR should maintain a state variable which indicate the 
>> consistency with respect to all others nodes.
> Well, one doesn't want such a state variable (because of the reasons
> below)and that was the historical reason to develop the concept of a
> "protocol" where you can change everything as long as the protocol
> didn't change.
I agree. In fact I think this is a problem of the application, or 
network management.
>> If the consistency is perfect then we can use the new 
>> downloaded/uploaded version, Otherwise we must wait....but until when?
>> The consistency means that every node runs the same OLSR version with 
>> the same configuration parameters.
> FunkFeuer has AFAIK an unknown number of OLSRD versions (from the last
> several years) in parallel (because it is a lot of work to update the
> firmware on dozens of nodes so it is at most done if someone fixes a
> problem there and the one is fed up with the old version) in the mesh
> (with "LinkQualityLevel 2" - it is much better in larger nets) and it
> works ATM.
I agree. But suppose the other side of the story. An enterprise, or a 
mesh network ruled out by one
authority. There are also other examples.
>> Does anyone implemented a technique to handle this problem?
> Personally I'm not fond of: updating software automatically on a net of
> (more or less) independent nodes run/managed by different people.
> <paranoid>I wouldn't allow something on my nodes (unless I'm in control
> of it).</paranoid>
> 	Bernd
As the previous.
This is another problem, I think it's related to security.
On the other hand, don't you allow your Linux/Windows machine to do 
automated download/update of new softwares?


Giuseppe De Marco, phD
Toyota Technological Institute
468-8511 Aichi 2-12-1 Hisakata, Tenpaku-ku, 
Nagoya, Japan
Email: demarco at toyota-ti dot ac dot jp
Tel (int): +81 (052)-809-1802
Skype-Id: giuseppe_dem2

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