简介
iperf3是一个网络速度测试工具，支持IPv4与IPv6，支持TCP、UDP、SCTP传输协议，可在Windows、Mac OS X、Linux、FreeBSD等各种平台使用，是一个简单又实用的小工具。 本文介绍安装、使用iperf3 网速测试工具。
安装iperf3
iperf3本身是以C++所开发的小程序，在官网https://iperf.fr/iperf-download.php上有提供各种平台的预编译二进制文件，解压缩后即可使用。
在CentOS 7上使用下列命令即可安装：
yum install iperf3MAC OS X上使用下列命令即可安装：
brew install iperf3网络带宽测试
在使用iperf3测试时，要同时在server端与client端都各执行一个程序，让它们互相传送报文进行测试。下面的例子是在CentOS7上进行的测试。
首先在10.23.5.66机器启动server端的程序：
iperf3 -s接着在10.23.5.65服务器上执行client 端的程序：
iperf3 -c 10.23.5.66在测试时server端与client端都会出现测试的数据，client端以下是测试的结果:
[jinguang1@localhost ~]$ iperf3 -c 10.23.5.66
Connecting to host 10.23.5.66, port 5201
[ 4] local 10.23.5.65 port 10412 connected to 10.23.5.66 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 114 MBytes 953 Mbits/sec 0 95.5 KBytes
[ 4] 1.00-2.00 sec 113 MBytes 948 Mbits/sec 0 95.5 KBytes
[ 4] 2.00-3.00 sec 113 MBytes 950 Mbits/sec 0 95.5 KBytes
[ 4] 3.00-4.00 sec 113 MBytes 948 Mbits/sec 0 95.5 KBytes
[ 4] 4.00-5.00 sec 113 MBytes 950 Mbits/sec 0 95.5 KBytes
[ 4] 5.00-6.00 sec 113 MBytes 948 Mbits/sec 0 95.5 KBytes
[ 4] 6.00-7.00 sec 113 MBytes 948 Mbits/sec 0 95.5 KBytes
[ 4] 7.00-8.00 sec 113 MBytes 950 Mbits/sec 0 95.5 KBytes
[ 4] 8.00-9.00 sec 113 MBytes 948 Mbits/sec 0 95.5 KBytes
[ 4] 9.00-10.00 sec 113 MBytes 950 Mbits/sec 0 95.5 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-10.00 sec 1.10 GBytes 949 Mbits/sec 0 sender
[ 4] 0.00-10.00 sec 1.10 GBytes 949 Mbits/sec receiveriperf Done.从打印的内容看，缺省参数下，Client将连接Server端的5201端口，持续向Server端发送数据，并统计出每秒传输的字节数、带宽、出现报文重传的次数、拥塞窗口（Congestion Window）大小，整个测试将持续10秒钟；最后将汇总10秒的平均数据，并给出发送和接收端的统计。
接下来分析一下Server的测试输出结果：
[jinguang1@localhost ~]$ iperf3 -s
warning: this system does not seem to support IPv6 - trying IPv4
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 10.23.5.65, port 10410
[ 5] local 10.23.5.66 port 5201 connected to 10.23.5.65 port 10412
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-1.00 sec 109 MBytes 913 Mbits/sec
[ 5] 1.00-2.00 sec 113 MBytes 948 Mbits/sec
[ 5] 2.00-3.00 sec 113 MBytes 949 Mbits/sec
[ 5] 3.00-4.00 sec 113 MBytes 949 Mbits/sec
[ 5] 4.00-5.00 sec 113 MBytes 949 Mbits/sec
[ 5] 5.00-6.00 sec 113 MBytes 949 Mbits/sec
[ 5] 6.00-7.00 sec 113 MBytes 949 Mbits/sec
[ 5] 7.00-8.00 sec 113 MBytes 949 Mbits/sec
[ 5] 8.00-9.00 sec 113 MBytes 949 Mbits/sec
[ 5] 9.00-10.00 sec 113 MBytes 949 Mbits/sec
[ 5] 10.00-10.04 sec 4.29 MBytes 947 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-10.04 sec 0.00 Bytes 0.00 bits/sec sender
[ 5] 0.00-10.04 sec 1.10 GBytes 945 Mbits/sec receiver
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Server端缺省监听IPv6地址和端口，如果未配置IPv6，会尝试IPv4。日志显示接收了来自10.23.5.65，源端口未10410的测试请求。Client端连续进行了10秒的测试，并显示了每秒传输的字节数，带宽信息；测试结束后会汇总发送和接收的统计信息。在Client连接关闭之后会继续侦听5201端口。
iperf3 进阶指令
iperf3 所提供的选项非常多，以下介绍一些常用的参数。
1. 测试时间和输出统计数据间隔
-t参数可以指定传输测试的持续时间，而-i可以指定统计输出的间隔时间，如需要持续测试一个小时，每10秒钟打印一次输出结果：
iperf3 -c server_ip -i 10 -t 36002. 储存测试结果
--logfile参数可以将输出的测试结果储存至文件中：
iperf3 -c server_ip --logfile stats.txt3. 设定侦听端口
iperf3缺省使用5201端口，如果需要指定，可以使用-p参数。这需要在Server和Client侧都需要进行指定，如使用12345端口：
#server侧
iperf3 -s -p 12345
#client侧
iperf3 -c server_ip -p 123454. JSON 格式输出
如果需要做一些自动化方面测试和管理工作，需要读取格式化的测试结果，那可以选择-J参数，来输出JSON格式测试结果。
[jinguang1@localhost ~]$ iperf3 -c 10.23.5.66 -J -t 2
{"start": {"connected": [{"socket": 4,"local_host": "10.23.5.65","local_port": 13346,"remote_host": "10.23.5.66","remote_port": 5201}],"version": "iperf 3.1.7","system_info": "Linux localhost.localdomain 3.10.0-862.9.1.el7.x86_64 #1 SMP Mon Jul 16 16:29:36 UTC 2018 x86_64","timestamp": {"time": "Fri, 07 Sep 2018 01:31:45 GMT","timesecs": 1536283905},"connecting_to": {"host": "10.23.5.66","port": 5201},"cookie": "localhost.localdomain.1536283905.522","tcp_mss_default": 1460,"test_start": {"protocol": "TCP","num_streams": 1,"blksize": 131072,"omit": 0,"duration": 2,"bytes": 0,"blocks": 0,"reverse": 0}},"intervals": [{"streams": [{"socket": 4,"start": 0,"end": 1.000059,"seconds": 1.000059,"bytes": 118546160,"bits_per_second": 948313208.319058,"retransmits": 0,"snd_cwnd": 97820,"rtt": 508,"omitted": false}],"sum": {"start": 0,"end": 1.000059,"seconds": 1.000059,"bytes": 118546160,"bits_per_second": 948313208.319058,"retransmits": 0,"omitted": false}}, {"streams": [{"socket": 4,"start": 1.000059,"end": 2.000063,"seconds": 1.000004,"bytes": 117912520,"bits_per_second": 943296336.710671,"retransmits": 0,"snd_cwnd": 97820,"rtt": 499,"omitted": false}],"sum": {"start": 1.000059,"end": 2.000063,"seconds": 1.000004,"bytes": 117912520,"bits_per_second": 943296336.710671,"retransmits": 0,"omitted": false}}],"end": {"streams": [{"sender": {"socket": 4,"start": 0,"end": 2.000063,"seconds": 2.000063,"bytes": 236458680,"bits_per_second": 945804841.588347,"retransmits": 0,"max_snd_cwnd": 97820,"max_rtt": 508,"min_rtt": 499,"mean_rtt": 503},"receiver": {"socket": 4,"start": 0,"end": 2.000063,"seconds": 2.000063,"bytes": 235998780,"bits_per_second": 943965299.700324}}],"sum_sent": {"start": 0,"end": 2.000063,"seconds": 2.000063,"bytes": 236458680,"bits_per_second": 945804841.588347,"retransmits": 0},"sum_received": {"start": 0,"end": 2.000063,"seconds": 2.000063,"bytes": 235998780,"bits_per_second": 943965299.700324},"cpu_utilization_percent": {"host_total": 3.365885,"host_user": 0.294900,"host_system": 3.447099,"remote_total": 0.054653,"remote_user": 0.003388,"remote_system": 0.049958},"sender_tcp_congestion": "cubic","receiver_tcp_congestion": "cubic"}
}5. 使用多条连接进行测试
-P参数可以指定同时连接测试的数量，缺省使用一条连接。
[jinguang1@localhost ~]$ iperf3 -c 10.23.5.66 -P 2 -t 2
Connecting to host 10.23.5.66, port 5201
[ 4] local 10.23.5.65 port 13652 connected to 10.23.5.66 port 5201
[ 6] local 10.23.5.65 port 13654 connected to 10.23.5.66 port 5201
[ ID] Interval Transfer Bandwidth Retr Cwnd
[ 4] 0.00-1.00 sec 56.8 MBytes 477 Mbits/sec 0 65.6 KBytes
[ 6] 0.00-1.00 sec 56.9 MBytes 478 Mbits/sec 0 67.0 KBytes
[SUM] 0.00-1.00 sec 114 MBytes 954 Mbits/sec 0
- - - - - - - - - - - - - - - - - - - - - - - - -
[ 4] 1.00-2.00 sec 56.5 MBytes 474 Mbits/sec 0 65.6 KBytes
[ 6] 1.00-2.00 sec 56.5 MBytes 474 Mbits/sec 0 67.0 KBytes
[SUM] 1.00-2.00 sec 113 MBytes 948 Mbits/sec 0
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth Retr
[ 4] 0.00-2.00 sec 113 MBytes 475 Mbits/sec 0 sender
[ 4] 0.00-2.00 sec 113 MBytes 474 Mbits/sec receiver
[ 6] 0.00-2.00 sec 113 MBytes 476 Mbits/sec 0 sender
[ 6] 0.00-2.00 sec 113 MBytes 474 Mbits/sec receiver
[SUM] 0.00-2.00 sec 227 MBytes 951 Mbits/sec 0 sender
[SUM] 0.00-2.00 sec 226 MBytes 949 Mbits/sec receiveriperf Done.6. 选择使用的传输协议
iperf3缺省使用TCP作为传输协议，如果使用UDP则使用-u参数，使用SCTP 则使用--sctp参数。
7. 反向传输
缺省iperf3使用上传模式：Client负责发送数据，Server负责接收；如果需要测试下载速度，则在Client侧使用-R参数即可。
