Re: [B.A.T.M.A.N.] is the multicast performance throttled?

["Linus Lüssing" <linus.luessing@c0d3.blue>]

On Thu, Aug 11, 2016 at 06:09:34PM +0200, Ignacio Quezada wrote:
> Hi Linus,
> 
> On tor, 2016-08-11 at 17:47 +0200, Linus Lüssing wrote:
> > Hi Ignacio,
> > 
> > Could you describe your setup a little more, just two devices?
> > What hardware are you using, which wifi cards? Which operating
> > system and version?
> > 
> > Which version of batman-adv are you using? What is your kernel
> > version?
> 
> The test environment is 2 android phones with Android 5.1 running
> kernel 3.4 where I backported batman 2016.2, same wifi chip (same soc)
> BCM4339.

Note sure how usable IBSS on Android is. Last time I heard someone
talking about it, it was supposedly unusable. But maybe someone
else has some more current information :-).

> 
> > What is a typical bitrate your wifi cards are agreeing on (iw
> > station dump)? What multicast rate have you configured for your
> > wifi cards?
> 
> Sadly, the support of iw for these kind of chipsets is very limited and
> iw dev wlan0 station dump returns nothing. I don't know how to get you
> that information.

And the multicast rate is still left at the 1MBit/s default?
Unfortunately, usually multicast packets are sent at the lowest
rate available as there are no wifi ACKs. To maximize the probability of
reception. There are some tweaks in OpenWRT though.

Also, often people change the bitrate from 1MBit/s to more like
12MBit/s or even above. That gives more free airtime and enhances the
batman-adv estimations (BATMAN IV).

> 
> > What software are you using for testing? What is the bitrate you
> > have configured in there? Is the unicast test UDP as well? What
> > bitrates are you able to achieve via TCP? Does a lower payload
> > length make any difference?
> > 
> 
> The software used is a java program with 1 socket each where one sends
> and the other receives. The unicast is UDP as well, yes. I haven't
> tried with TCP but I can do it if it is necessary, my application only
> relies on UDP.

UDP has no flow control. That's why I was asking about the bitrate
you have configured in the application. Sending with "as fast as
possible" will basically jam your (and your neighbors) wifi. And
will create trouble for batman-adv to find usable routes too
without any airtime available.

Regards, Linus