Hello,
I am running a test on two windows machines that are connected to each other
through a local Gigabit 8-port switch. One is a Dell power edge Windows 2003
server and one is an XP laptop. Ports on both machines are running at 1Gbps and
they have no other apps running on them besides iperf. Windows 2003 server is
acting as an iperf server and the laptop is acting as client
When I run udp test using ‘-b100m’ on the client with server running in
default, I get about 95Mbps throughput but with lots of dropped packets. I
then start to increase the buffer size on both ends and find that at buffer
size of ‘-w32MB’ dropped packets get down to zero. To find max.udp throughput
on the 1Gbps link, I increased the bandwidth gradually to ‘the max. of –b2147m’
and found that the client would not even send anything faster than 115Mbps
regardless of what I set the buffer size to be. It was only when I decreased
the datagram size to ‘-l900B’ on both ends that the client started sending data
at about 700Mbps (even then it was inconsistent –kept varying from
500-800Mbps-).
How does iperf use “b, w and l” parameters? Is there a way I can calculate or
estimate their value in order to achieve max. UDP throughput for a given link?
Below are some samples from my test (server reports for each are at the bottom):
Thank you,
Yousuf,
C:\Iperf>iperf -c10.10.10.80 -u -i1 -b100m -w16KB
------------------------------------------------------------
Client connecting to 10.10.10.80, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 16.0 KByte
------------------------------------------------------------
[1912] local 10.10.10.81 port 1680 connected with 10.10.10.80 port 5001
[ ID] Interval Transfer Bandwidth
[1912] 0.0- 1.0 sec 10.9 MBytes 91.2 Mbits/sec
[1912] 1.0- 2.0 sec 11.8 MBytes 98.9 Mbits/sec
[1912] 2.0- 3.0 sec 11.8 MBytes 98.9 Mbits/sec
[1912] 3.0- 4.0 sec 11.8 MBytes 98.9 Mbits/sec
[1912] 4.0- 5.0 sec 11.6 MBytes 97.4 Mbits/sec
[1912] 5.0- 6.0 sec 11.4 MBytes 95.8 Mbits/sec
[1912] 6.0- 7.0 sec 11.1 MBytes 92.7 Mbits/sec
[1912] 7.0- 8.0 sec 11.2 MBytes 94.3 Mbits/sec
[1912] 8.0- 9.0 sec 11.4 MBytes 95.8 Mbits/sec
[1912] 9.0-10.0 sec 11.2 MBytes 94.3 Mbits/sec
[1912] 0.0-10.0 sec 114 MBytes 95.7 Mbits/sec
[1912] Server Report:
[1912] 0.0-10.0 sec 112 MBytes 93.8 Mbits/sec 0.000 ms 1882/81491 (2.3%)
[1912] Sent 81491 datagrams
C:\Iperf>iperf -c10.10.10.80 -u -i1 -b100m -w1024KB
------------------------------------------------------------
Client connecting to 10.10.10.80, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 1.00 MByte
------------------------------------------------------------
[1912] local 10.10.10.81 port 1737 connected with 10.10.10.80 port 5001
[ ID] Interval Transfer Bandwidth
[1912] 0.0- 1.0 sec 11.2 MBytes 94.3 Mbits/sec
[1912] 1.0- 2.0 sec 11.4 MBytes 95.8 Mbits/sec
[1912] 2.0- 3.0 sec 11.5 MBytes 96.9 Mbits/sec
[1912] 3.0- 4.0 sec 11.7 MBytes 97.9 Mbits/sec
[1912] 4.0- 5.0 sec 12.0 MBytes 100 Mbits/sec
[1912] 5.0- 6.0 sec 11.8 MBytes 98.9 Mbits/sec
[1912] 6.0- 7.0 sec 11.8 MBytes 98.9 Mbits/sec
[1912] 7.0- 8.0 sec 11.4 MBytes 95.8 Mbits/sec
[1912] 8.0- 9.0 sec 11.2 MBytes 94.3 Mbits/sec
[1912] 9.0-10.0 sec 11.2 MBytes 94.3 Mbits/sec
[1912] 0.0-10.0 sec 115 MBytes 96.6 Mbits/sec
[1912] Server Report:
[1912] 0.0-10.0 sec 115 MBytes 96.8 Mbits/sec 0.000 ms 0/82287 (0%)
[1912] Sent 82287 datagrams
C:\Iperf>iperf -c10.10.10.80 -u -i1 -b2147m -w32MB
------------------------------------------------------------
Client connecting to 10.10.10.80, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 32.0 MByte
------------------------------------------------------------
[1912] local 10.10.10.70 port 2323 connected with 10.10.10.80 port 5001
[ ID] Interval Transfer Bandwidth
[1912] 0.0- 1.0 sec 13.8 MBytes 116 Mbits/sec
[1912] 1.0- 2.0 sec 14.0 MBytes 117 Mbits/sec
[1912] 2.0- 3.0 sec 14.2 MBytes 119 Mbits/sec
[1912] 3.0- 4.0 sec 14.3 MBytes 120 Mbits/sec
[1912] 4.0- 5.0 sec 14.0 MBytes 118 Mbits/sec
[1912] 5.0- 6.0 sec 14.2 MBytes 119 Mbits/sec
[1912] 6.0- 7.0 sec 13.6 MBytes 114 Mbits/sec
[1912] 7.0- 8.0 sec 13.6 MBytes 114 Mbits/sec
[1912] 8.0- 9.0 sec 13.8 MBytes 115 Mbits/sec
[1912] 9.0-10.0 sec 13.8 MBytes 116 Mbits/sec
[1912] 0.0-10.0 sec 139 MBytes 117 Mbits/sec
[1912] Server Report:
[1912] 0.0-10.0 sec 139 MBytes 117 Mbits/sec 1.201 ms 0/99331 (0%)
[1912] Sent 99331 datagrams
C:\Iperf>iperf -c10.10.10.80 -u -i1 -b2147m -w32MB -l900B
------------------------------------------------------------
Client connecting to 10.10.10.80, UDP port 5001
Sending 900 byte datagrams
UDP buffer size: 32.0 MByte
------------------------------------------------------------
[1912] local 10.10.10.70 port 2325 connected with 10.10.10.80 port 5001
[ ID] Interval Transfer Bandwidth
[1912] 0.0- 1.0 sec 80.5 MBytes 675 Mbits/sec
[1912] 1.0- 2.0 sec 101 MBytes 844 Mbits/sec
[1912] 2.0- 3.0 sec 99.6 MBytes 836 Mbits/sec
[1912] 3.0- 4.0 sec 104 MBytes 869 Mbits/sec
[1912] 4.0- 5.0 sec 102 MBytes 854 Mbits/sec
[1912] 5.0- 6.0 sec 104 MBytes 873 Mbits/sec
[1912] 6.0- 7.0 sec 93.1 MBytes 781 Mbits/sec
[1912] 7.0- 8.0 sec 102 MBytes 852 Mbits/sec
[1912] 8.0- 9.0 sec 93.6 MBytes 785 Mbits/sec
[1912] 9.0-10.0 sec 77.9 MBytes 653 Mbits/sec
[1912] 0.0-10.2 sec 956 MBytes 785 Mbits/sec
[1912] Server Report:
[1912] 0.0-10.2 sec 956 MBytes 787 Mbits/sec 19.225 ms 0/1114043 (0%)
[1912] Sent 1114043 datagrams
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