Re: [B.A.T.M.A.N.] broadcast storms

[Simon Wunderlich <sw@simonwunderlich.de>]

[-- Attachment #1: Type: text/plain, Size: 1684 bytes --]

On Tuesday, November 13, 2018 2:55:31 PM CET Jake.Harris@zf.com wrote:
> > Mhm, this is really not much data ... did you try the multicast as
> > suggested in an earlier reply?
> What earlier reply are you referring to? The only one I'm noticing is the
> tip to boost the multicast bandwidth, but I cannot see this being fruitful
> to update the configuration of all 50 nodes when worst-case I'm using less
> than 1% of the max throughput.

One aspect is that the multicast rate is also changing the modulation rate of 
beacons. If you have >50 nodes beaconing with 1 Mbit/s you are already filling 
up your airtime with beacons. Do the math - one beacon takes about 1ms on 1 
Mbit/s, each node sends about 10 beacons per second ...

This is actually very important and will most likely help already. It would be 
a better fix than changing the protection window.

> > BATADV_RESET_PROTECTION_MS is a define in the batman-adv C-code, so it
> > can't be set at runtime but only at compile time.
> While this sounds like an utter pain in the butt to recompile and update the
> code on all the nodes to make this change, I believe this has a far better
> chance of alleviating the issue, I'm looking into how to do this since I've
> never compiled anything myself but I can't see it being too difficult.
> 
> One observation I made when rebooting the swarm all at once, about a minute
> after all the pi's go down the laptop I work off (running batctl td bat0)
> reports a whole bunch of backbone unannounced messages I believe. I'm
> assuming there is one message per node but have not verified, my guess is
> this is normal and is not the cause of these issues?
> 
> Again, thank you


[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 833 bytes --]