[Olsr-users] route instability

Kim Hawtin (spam-protected)
Thu Sep 13 06:33:30 CEST 2007

Hi Gian,

Gian Maria Giani wrote:
> We have some problems with a network running OLSR v.0.4.10, in that the
> routes are not very stable.
> The problem seems strange. The main points are:
> -          the network contains 10 nodes. They are in fixed positions.
> Each node has about 3 neighbours, and the maximum distance between nodes is 3
> hops.
> -          the routes are not stable. If one observes the routing table
> of one node in a given moment in time, and then observes it again after
> some seconds, many times the observed routes are different
> -          this seems related to the fact that some neighbors are listed
> as non-symmetric (they appear as symmetric for some moments, then appear as
> asymmetric, then again as symmetric)
> -          the percentage of lost packets over these asymmetric links,
> however, is 0% in both directions
> We have already tried in many ways to solve the problem... in particular
> we have increased the validity time of hello messages up to 60 seconds,
> but the problem is still there. Any idea?

I recently did a demo for my local linux user group, and we noticed this
behaviour too.

So we had a look at the link quality (LC) settings. After enabling LC
the route map stability was significantly improved.

You can visualise the route map with dot-draw and the perl script from
here; http://wirelessafrica.meraka.org.za/wiki/index.php/OLSR_Dot_Draw

Info from the LinuxSA is demo here;

Compare the second and third diagrams;
 the second did not use LC
 the third used LC=2

have fun,

Operating Systems, Services and Operations
Information Technology Services, The University of Adelaide

"I am not a finite state machine"

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