[OLSR-users] unstable routing tables with 0.4.8

[Thomas Lopatic]

Hi Franca,

Your application traffic is probably unicast traffic, whereas OLSR
traffic is broadcast traffic. For unicast frames 802.11 uses
acknowledgements and retransmits a frame if it is not acknowledged. For
broadcast frames no such mechanism exists. Hence, in 802.11 unicast
traffic is inherently more reliable than broadcast traffic. If there's
packet loss on a link, broadcast packets are more prone to loss than
unicast packets.

What you experience might be that your application traffic increases the
load on your wireless links substantially, which in turn leads to an
increasing number of lost frames on your links. As menioned above, OLSR
traffic will suffer more than your application traffic from this decay
in link quality. Apparently, in your scenario, hardly any OLSR broadcast
packets make it through the air, once your application starts sending
unicast traffic.

What you might want to do:

* Decrease the intervals for OLSR message emission, e.g. the HELLO
interval, so that OLSR nodes transmit OLSR packets more often.

* Increase the validity times for OLSR messages, e.g. the HELLO validity
time, such that a couple of lost messages do not result in expired links.

Could you send your configuration file? I'll then be able to come up
with more detailed suggestions.

-Thomas