[olsr-dev] Re: [OLSR-users] Differing metrics for route decision

Sven-Ola Tuecke (spam-protected)
Mon Feb 27 14:34:11 CET 2006

One more (sorry to nerve wreck everybody),

most of our routings loops are caused by overloaded devices - since packets 
are dropped because the thing does repeat the dijstra calculation too fast. 
Visible effect: 30-50% packet loss on ethernet wires. So that unmentioned 
directive may be the thing to have here.

Other remark: This weekend I was able to solve the BSSID-split-in-Ad-Hoc 
thing for Broadcom Wifi. Have two WRTs talking to each other in my bedroom 
on our olsr.freifunk.net SSID, but they don't care about other becons flying 
around. Means: No more unpredictable channel switches, no BSSID wars, no 
fallback-to-b-mode-only, no hacking with TSF=500.000 years etc. To be 
evaluated next wednesday in the c-base Wifi-hell where a couple of PCMCIA 
card owners normally bring the local area down :)

LG Sven-Ola

"Thomas Lopatic" <(spam-protected)> schrieb im Newsbeitrag 
> Hey Sven-Ola,
>> Alone the dijstra algo is the most expensive part now -> will be very
>> hairy to optimize that. Hence a question: Is it possible to slow down
>> the "dijstra-rate"? E.g. a 10 seconds Net-Info-Collection phase followd
>> by a single dijkstra calculation...? Or do OLSRd need to work on any
>> single change here?
> Ha! I've been hoping for a long time that somebody would finally ask
> this question on the mailing list, as this gives me the chance to show
> off our "LinkQualityDijkstraLimit" configuration directive. :-) It's
> basically fish-eye in reverse. Let's look at an example.
>  LinkQualityDijkstraLimit 5 10
> olsrd will then collect TC information and update its internal data
> structures just like before, but only TCs from nodes less than 5 hops
> away will actually trigger a Dijkstra run.
> In addition to the Dijkstra runs triggered by incoming TCs from nodes
> less than 5 hops away, every 10 seconds an additional Dijkstra run will
> be triggered. Just in case there haven't been any Dijkstra runs for 10
> seconds.
> So, to achieve the desired behaviour, simply say
>  LinkQualityDijkstraLimit 0 10
> This will switch off Dijkstra runs triggered by TC messages and only run
> Dijkstra every 10 seconds.
> Be aware, however, that this could lead to routing loops in a network
> that frequently changes its topology.
> -Thomas
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