Curious if iperf2  <https://sourceforge.net/projects/iperf2/>exhibits
similar behavior?  It shouldn't have an issue with low packet rates.

Bob


On Mon, Apr 16, 2018 at 2:25 PM, Bruce A. Mah <b...@es.net> wrote:

> If memory serves me right, Michael Fox wrote:
> > The iperf3 bandwidth option doesn't seem to work (or perhaps I'm not
> using
> > it correctly).
> >
> > iPerf3 version 3.1.3 on Ubuntu server and Windows client.
> >
> > I'm trying to test radio links at various bandwidths, ranging from 32
> Kbps
> > to 400 Kbps, and various packet sizes, ranging from 256 to 1520 bytes.
> But
> > setting the bandwidth down to the link bandwidth (or lower) doesn't slow
> the
> > output from the client.
> >
> > Example:  In the example below, bandwidth is clearly set at 128K, but
> > resulting bandwidth in 200K.
> >
> > How do I get the iperf client to only send at the specified rate?
>
> I think the #1 thing you should try is to get newer executables of
> iperf3.  Starting with iperf-3.2 (3.5 is current now) we re-tuned a
> bunch of stuff with how the transmitter side paces stuff (or rather we
> made it so it isn't so horribly broken).  The use cases where this
> really helps is for UDP, which tended to send packets in huge bursts,
> and also had difficulty sending at very low bitrates as you are doing.
> (iperf3 was originally designed for high-speed environments, such as
> multiple-10Gbps.)
>
> If this doesn't work, sending smaller packets might help, although I
> think controlling the packet size is part of your tests, so that might
> not be feasible.
>
> Bruce.
>
> >> iperf3 -c 192.168.8.10 -u -l 1472 -b 128K
> > Connecting to host 192.168.8.10, port 5201
> > [  4] local 192.168.7.147 port 59396 connected to 192.168.8.10 port 5201
> > [ ID] Interval           Transfer     Bandwidth       Total Datagrams
> > [  4]   0.00-1.00   sec  25.9 KBytes   212 Kbits/sec  18
> > [  4]   1.00-2.00   sec  24.4 KBytes   200 Kbits/sec  17
> > [  4]   2.00-3.00   sec  24.4 KBytes   200 Kbits/sec  17
> > [  4]   3.00-4.00   sec  25.9 KBytes   212 Kbits/sec  18
> > [  4]   4.00-5.00   sec  21.6 KBytes   177 Kbits/sec  15
> > [  4]   5.00-6.00   sec  24.4 KBytes   200 Kbits/sec  17
> > [  4]   6.00-7.00   sec  21.6 KBytes   176 Kbits/sec  15
> > [  4]   7.00-8.00   sec  24.4 KBytes   200 Kbits/sec  17
> > [  4]   8.00-9.00   sec  23.0 KBytes   189 Kbits/sec  16
> > [  4]   9.00-10.00  sec  23.0 KBytes   188 Kbits/sec  16
> > - - - - - - - - - - - - - - - - - - - - - - - - -
> > [ ID] Interval           Transfer     Bandwidth       Jitter
> Lost/Total
> > Datagrams
> > [  4]   0.00-10.00  sec   239 KBytes   195 Kbits/sec  0.049 ms  0/165
> (0%)
> > [  4] Sent 165 datagrams
> >
> > iperf Done.
> >
> >
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>
>
>
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