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

[Ignacio Quezada <dreamtrick@gmail.com>]

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.

> 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.

> 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.

I just tried a lower payload (504 bytes) and the amount of packets per
second becomes considerably higher but the amount of data is still
almost the same.

> Regards, Linus
> 
> 
> On Thu, Aug 11, 2016 at 05:13:01PM +0200, Ignacio Quezada wrote:
> > 
> > Hello,
> > I am trying to build an application using UDP multicast sockets
> > based
> > on a network mesh built with devices connected in IBSS mode. 
> > 
> > The kernel documentation says that this was the place to ask
> > questions
> > or anything :).
> > 
> > Testing the application in the mentioned environment, it suffers
> > some
> > kind of throttling or buffering limiting the throughput. Testing
> > with
> > my application, without the batman interface, just 2 IBSS connected
> > devices, the multicast rate goes around 100kb/s (not saying that
> > the
> > wifi link actually tops at that speed), but then just to add the
> > batman-adv interface and use that instead, the multicast rate
> > becomes
> > unstable between 0-20kb/s.
> > 
> > Disabling multicast optimization, it changes a bit the behaviour
> > but
> > still the same speed.
> > 
> > If I change the multicast packet to a unicast packet, both setups
> > achieve the same speed (~100kb/s), so the batman interface is
> > working
> > but the multicast packets are being handled in a different way. Is
> > it
> > supposed to be like that?
> > 
> > The packets are sent right away according to the iptables counter
> > of
> > packets as well as tcpdump, but the receiver only gets them in a
> > very
> > slow way (counting but not calculating, I think it is around 8
> > packets
> > per second).
> > The MTU is set as advised, 1532 and the payload for the UDP packets
> > is
> > as big as it can be so the packet does not get fragmented.
> > 
> > Any way to increase the rate or disabling the throttling?
> > -- 
> > 
> > MVH
> > Ignacio Quezada

--

MVH
Ignacio Quezada