Iperf ignoring "UDP buffer size" and "TCP window size"

If I execute Iperf(version 2.0.5 (08 Jul 2010) pthreads) client with
"iperf -c 192.168.2.1 -u -fm -t60 -d -b 10m -w 4m" command, Iperf
server with "iperf -s u -w 4m" command, Iperf client with "iperf -c
192.168.1.1 -t 60 -w 2m" command etc, I get the "TCP window size: 50.0
KByte (WARNING: requested 2.00 MByte)", "UDP buffer size: 0.01 MByte
(WARNING: requested 4.00 MByte)" or similar warning. In other words
the value of the "-w" flag seems to be ignored. One example:

[root <at>  ~]# iperf -c 192.168.2.1 -u -fm -t60 -d -b 10m -w 4M
------------------------------------------------------------
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size: 0.04 MByte (WARNING: requested 4.00 MByte)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.2.1, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 0.01 MByte (WARNING: requested 4.00 MByte)
------------------------------------------------------------
[  4] local 192.168.1.1 port 31589 connected with 192.168.2.1 port 5001
[  3] local 192.168.1.1 port 5001 connected with 192.168.2.1 port 38678

What might cause this?

I Googled with 'iperf "WARNING: requested *"', but found anything useful.

regards,
martin

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Re: Iperf ignoring "UDP buffer size" and "TCP window size"

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Re: Iperf ignoring "UDP buffer size" and "TCP window size"

On Mon, 4 Apr 2011, Martin T wrote:

> If I execute Iperf(version 2.0.5 (08 Jul 2010) pthreads) client with
> "iperf -c 192.168.2.1 -u -fm -t60 -d -b 10m -w 4m" command, Iperf
> server with "iperf -s u -w 4m" command, Iperf client with "iperf -c
> 192.168.1.1 -t 60 -w 2m" command etc, I get the "TCP window size: 50.0
> KByte (WARNING: requested 2.00 MByte)", "UDP buffer size: 0.01 MByte
> (WARNING: requested 4.00 MByte)" or similar warning. 

This warning message means that your operating system denies the
request from iperf. Probably because your request is deemed too big
and would consume too much kernel memory. You either need to configure
your operating system to be more generous, or be less greedy yourself.

Marc.

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Re: Iperf ignoring "UDP buffer size" and "TCP window size"

Hi Martin,

Iperf isn't ignoring the -w flag, it's asking the OS for 4M of space
but the OS is denying the request.  Most likely this is due to the
limits on the system being set too low.  You can find information on
raising those limits on this page:

http://fasterdata.es.net/fasterdata/host-tuning/

Jon

On Mon, Apr 4, 2011 at 7:38 AM, Martin T <m4rtntns@...> wrote:
> If I execute Iperf(version 2.0.5 (08 Jul 2010) pthreads) client with
> "iperf -c 192.168.2.1 -u -fm -t60 -d -b 10m -w 4m" command, Iperf
> server with "iperf -s u -w 4m" command, Iperf client with "iperf -c
> 192.168.1.1 -t 60 -w 2m" command etc, I get the "TCP window size: 50.0
> KByte (WARNING: requested 2.00 MByte)", "UDP buffer size: 0.01 MByte
> (WARNING: requested 4.00 MByte)" or similar warning. In other words
> the value of the "-w" flag seems to be ignored. One example:
>
> [root <at>  ~]# iperf -c 192.168.2.1 -u -fm -t60 -d -b 10m -w 4M
> ------------------------------------------------------------
> Server listening on UDP port 5001
> Receiving 1470 byte datagrams
> UDP buffer size: 0.04 MByte (WARNING: requested 4.00 MByte)
> ------------------------------------------------------------
> ------------------------------------------------------------
> Client connecting to 192.168.2.1, UDP port 5001
> Sending 1470 byte datagrams
> UDP buffer size: 0.01 MByte (WARNING: requested 4.00 MByte)

Re: Iperf ignoring "UDP buffer size" and "TCP window size"

Jon, Marc:

thank you for information! I modified following kernel parameters:

#UDP socket receive buffer
net.ipv4.udp_rmem_min
#UDP socket send buffer
net.ipv4.udp_wmem_min
#TCP socket receive max buffer size
net.core.rmem_max
#TCP socket send max buffer size
net.core.wmem_max

..under Debian like this(all values are in bytes):

test: ~# sysctl -w net.ipv4.udp_rmem_min=4194304
net.ipv4.udp_rmem_min = 4194304
test: ~# sysctl -w net.ipv4.udp_wmem_min=4194304
net.ipv4.udp_wmem_min = 4194304
test: ~# sysctl -w net.core.rmem_max=8388608
net.core.rmem_max = 8388608
test: ~# sysctl -w net.core.wmem_max=8388608
net.core.wmem_max = 8388608
test: ~#

Please correct me if those kernel parameters are not the correct
ones(I doubt about "net.ipv4.udp_rmem_min" and "net.ipv4.udp_wmem_min"
because of "_min") or if values are stupid.

However, I managed to start both Iperf server and client in both TCP

Re: Iperf ignoring "UDP buffer size" and "TCP window size"

Martin,

 This should answer your Linux tuning questions:

http://www.psc.edu/networking/projects/tcptune/#Linux

Cheers,

Marc

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Re: Iperf ignoring "UDP buffer size" and "TCP window size"

Excerpts from Martin T's message of Wed Apr 06 18:43:12 -0500 2011:
> Jon, Marc:
> 
> thank you for information! I modified following kernel parameters:
> 
> #UDP socket receive buffer
> net.ipv4.udp_rmem_min
> #UDP socket send buffer
> net.ipv4.udp_wmem_min
> #TCP socket receive max buffer size
> net.core.rmem_max
> #TCP socket send max buffer size
> net.core.wmem_max
> 
> ..under Debian like this(all values are in bytes):
> 
> test: ~# sysctl -w net.ipv4.udp_rmem_min=4194304
> net.ipv4.udp_rmem_min = 4194304
> test: ~# sysctl -w net.ipv4.udp_wmem_min=4194304
> net.ipv4.udp_wmem_min = 4194304
> test: ~# sysctl -w net.core.rmem_max=8388608
> net.core.rmem_max = 8388608
> test: ~# sysctl -w net.core.wmem_max=8388608
> net.core.wmem_max = 8388608
> test: ~#
> 
> 
> Please correct me if those kernel parameters are not the correct
> ones(I doubt about "net.ipv4.udp_rmem_min" and "net.ipv4.udp_wmem_min"
> because of "_min") or if values are stupid.

sender reachs 54M to send packets when link disconnect (802.11g)

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Re: sender reachs 54M to send packets when link disconnect (802.11g)

Hi,

   What seems to happen is that your sending operating system is 
dropping all the packets internally. Since UDP is not reliable your 
operating system is perfectly allowed to do that.

How would you like your operating system to behave instead?

Cheers,

Marc

On Wed, 20 Apr 2011, 清 廖 wrote:

> Dear all,
> I use 802.11g and 54M bandwidth to send udp packet.
> 
> When I use only one transmit link to send udp packet, the sender shows the bandwidth is about 24M and the
> receiver shows the throughput is also about 24M and lost packet is 0%. I thinks it is normal.
> 
> But when I use two transmit links to send udp packet in the same channel, the sender shows the bandwidth is 54M
> and receiver shows the throughput is very low and the lost packet percentage is about 100%.
> 
> Furthermore, when link disconnects the sender also reach 54M to send packets.
> 
> Could anyone tell me why the sender will reach 54M to send packets when link disconnect or packet loss is high?
> Thanks a lot！
> 
> Best,
> Qing
> 
> 

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udp bandwidth in iperf

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