Iperf TCP throughput measurement result
Hi, All:
I am currently evaluating a high-performance radio (~300 Mbps) in the lab environment (short distance) using Iperf. I am seeing different throughput results with 1 client and 5 clients.
Here is the one-way and two-way results shown below.
1. One-way throughput
* Testing with one client
* ------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 65.0 KByte
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.100.2, TCP port 5001
TCP window size: 65.0 KByte (WARNING: requested 65.0 KByte)
------------------------------------------------------------
[ 5] local 192.168.100.1 port 50475 connected with 192.168.100.2 port 5001
[ 5] 0.0-120.0 sec 1.99 GBytes 143 Mbits/sec
[ 4] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 56734
[ 4] 0.0-120.0 sec 2.00 GBytes 143 Mbits/sec
* Testing with five cleints (-P5)
* ------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 65.0 KByte
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.100.2, TCP port 5001
TCP window size: 65.0 KByte (WARNING: requested 65.0 KByte)
------------------------------------------------------------
[ 5] local 192.168.100.1 port 65130 connected with 192.168.100.2 port 5001
[ 3] local 192.168.100.1 port 50815 connected with 192.168.100.2 port 5001
[ 4] local 192.168.100.1 port 63251 connected with 192.168.100.2 port 5001
[ 9] local 192.168.100.1 port 64820 connected with 192.168.100.2 port 5001
[ 6] local 192.168.100.1 port 57045 connected with 192.168.100.2 port 5001
[ 3] 0.0-120.0 sec 631 MBytes 44.1 Mbits/sec
[ 4] 0.0-120.0 sec 652 MBytes 45.6 Mbits/sec
[ 6] 0.0-120.0 sec 649 MBytes 45.4 Mbits/sec
[ 9] 0.0-120.0 sec 649 MBytes 45.4 Mbits/sec
[ 5] 0.0-120.0 sec 639 MBytes 44.7 Mbits/sec
[SUM] 0.0-120.0 sec 3.14 GBytes 225 Mbits/sec
[ 8] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 64349
[ 3] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 55116
[ 4] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 51162
[ 5] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 58124
[ 6] local 192.168.100.1 port 5001 connected with 192.168.100.2 port 50025
[ 3] 0.0-120.0 sec 647 MBytes 45.2 Mbits/sec
[ 8] 0.0-120.0 sec 655 MBytes 45.8 Mbits/sec
[ 5] 0.0-120.0 sec 640 MBytes 44.7 Mbits/sec
[ 4] 0.0-120.0 sec 656 MBytes 45.8 Mbits/sec
[ 6] 0.0-120.0 sec 616 MBytes 43.0 Mbits/sec
[SUM] 0.0-120.0 sec 3.14 GBytes 225 Mbits/sec
My question is that what could cause the Iperf to have better throughput when 5 clients run at the same time. One speculation is that the radio under evulation has dynamic TDD feature, which leads to a variable latency. And the OS cannot cope well with a variable latency.
Based on my knowledge, even though it is fat pipe, I test the radios in very short distance. I don't think it has anything to do with TCP tuning.
Any comments on this issue will be appreciated.
Jin Fan