[Olsr-users] Suggested OLSR Timer Values

[Henning Rogge]

Am Friday 13 February 2009 05:55:32 schrieb Bhat, Ishwara:
> Hi,
>
> I have a question about OLSR timers. My usage mode is such that
>
> 1.	All newly joined nodes shall be known within 1 second.
> 2.	Any node dropped out of network shall be known in 1 second.
> (Mandatory for 1-hop links. Other mesh nodes- 1 sec desired; But can be
> delayed).
> 3.	I have only 4 nodes in this mode, mostly in linear topology.
>
> What is the suggested timer values?
>
> HelloInterval 0.5
> HelloValidity 0.5
> TC Interval  0.5
> TCValidity Interval   0.5
It cannot work this way... set the validity time AT LEAST to 5 times the 
corresponding interval.

Try something like this:

HelloInterval 0.2
HelloValidity 2.0
TCInterval 0.5
TCValidity 3

This values will only work for small networks, but they should increase the 
speed of node detection and deletion.
Do NOT use etx_ff (it only creates ONE LQ value each second), use etx_fpm as 
your lq algorithm.

> When I tested in a 2 node system,
>
> 1.	The hellos seem to work well in recognizing the new nodes.
> 2.	But for loss of any existing node, it appears to take about 5
> seconds.
>
> I was hoping that since upon TCValidity expiry, mesh would expect fresh
> topology info and would invalidate existing information.

> I observed that irrespective of timers the 1-hop links are retained till
> ETX is 3. (Just that with shorter timers, the value is calculated more
> frequently and this has some effect on the link loss declaration. But
> still could not detect link loss in a second).
With validity = interval you sometimes loose a hello link just because you 
missed a single hello !

> Please tell me what values would achieve the link loss detection of 1 or
> 2 seconds.
>
> Also with short TC timers won't the control traffic choke the network ?
> While using OLSR should I resist any specification of the order of 1
> second ?
Of course it will. That's the tradeof.

No, OLSR will work fine with highspeed settings, but you should keep your 
network small.

Henning

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