Hi Vignesh,
The way iperf works is the client makes a tcp connection to the server, and
sends 10 seconds worth of data. However, the client-side kernel is buffering
that data up, and sending it, and, in the case of loss, resending it. If you
have a very lossy connection, it may take far more than 10 seconds for the
server to receive '10 seconds' worth of data. If you add a '-i 2' to the server
side command-line, you can see the rate it's receiving the data at every 2
seconds which should help you see what's happening.
Cheers,
Aaron
On Jul 16, 2012, at 6:10 AM, vignesh venkateswaran wrote:
> I am using Iperf 2.0.4 on linux 2.6.32.10 loaded in two Mikrotik Routerboards
> 411AR.
> I tried to run iperf in these two boards through serial connections from the
> boards to my laptop via minicom and measure the 802.11 performance.
> When I run iperf tcp test setting one board as server and another as client,
> I can see only
> the following message:
>
> root@OpenWrt:/# iperf -s
> ------------------------------
> ------------------------------
> Server listening on TCP port 5001
> TCP window size: 85.3 KByte (default)
> ------------------------------------------------------------
> [ 4] local 192.168.1.20 port 5001 connected with 192.168.1.6 port 41061
>
>
> root@OpenWrt:/# iperf -c 192.168.1.20
> ------------------------------------------------------------
> Client connecting to 192.168.1.20, TCP port 5001
> TCP window size: 16.0 KByte (default)
> ------------------------------------------------------------
> [ 3] local 192.168.1.6 port 41061 connected with 192.168.1.20 port 5001
>
>
> At this point, the client hangs and the results are not displayed, not even
> much later
> than 10 secs. Sometimes, the results are displayed after arbitrary time
> intervals like
> 17.4 secs, 1092.2 secs and so on.
>
> UDP works fine. I get the results exactly after 10 secs.
>
> Can somebody identify the problem behind this and also suggest an appropriate
> solution?
>
>
> Vignesh
>
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