[Olsr-users] INFINITE cost in all links

Antonio Anselmi (spam-protected)
Wed Jul 30 19:47:44 CEST 2014

2014-07-30 19:35 GMT+02:00 Henning Rogge <(spam-protected)>:

> On Tue, Jul 29, 2014 at 2:37 PM, Antonio Anselmi <(spam-protected)>
> wrote:
> > hi Ben, nice to read you again!
> >
> > running olsrd with the minimal (default) configuration will be the first
> > step for debugging, in addition to compile olsrd with the flag
> > NO_DEBUG_MESSAGES=0 (Openwrt Makefile). This way, as soon as that
> condition
> > occurs, we'll try to grab the debug lines for off-line examination based
> on
> > a well-known configuration.
> > Unfortunatelly, we can't reproduce the "ETX=infinite situation" and the
> > interested networks are all production networks that serve several user
> > connections.
> If the production network Olsrd crashs anyways you could start it
> there with logging activated and then pipe the stderr output into some
> ringbuffer so you only see the end when it crashes again.
> > By the way, we noticed that "ETX=infinite" occurs more frequently when
> the
> > olsrd-gateway manages about a hundred connections from the users
> associated
> > to the APs of the meshed nodes (every mesh node runs a second VAP in
> master
> > mode): so the rate of that error, if I may say so, seems to be related to
> > the traffic/connections.
> > The more a node is under load the more is its
> > latency, then it begins to lose packets and its LQ decreases, routes
> change
> > and TC propagates the changes.
> Could it be that the outgoing interface is congested to that Olsrd
> cannot get its own packets out? If the outgoing UDP buffer of Olsrd
> fills up it will just drop packets at some point.
> Are you using prioritization for the Olsr UDP port?

that's an interesting point, it could make the difference.
Do you know examples about tc implementation that prioritizes UDP packets?

> > Maybe incorrect timings could cause slow
> > refreshes of the routing tables so that a loop could occur?
> No. Unless the system clock misbehaves the timing should be stable.
> > But all the
> > nodes and all at the same time?... unlikely. Moreover, the gateway node
> - as
> > I wrote - continues to receive olsrd packets, sign that the other nodes
> are
> > alive.
> Henning

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