measuring network latency between nodes

I'll use iperf tool, which is available in the EPEL repo if you're using RH/CentOS.

Installation is pretty straightforward :

# yum -y install iperf

For use, you'll have to execute one instance on the first machine as the server, and another on the other machine as the client.

Execute as a server (-s) on port (-p) 2000 :

[root@machine01 ~]# iperf -s -p 2000
------------------------------------------------------------
Server listening on TCP port 2000
TCP window size: 85.3 KByte (default)


Now execute client on the other machine for 25 seconds (-t 25) with 5 seconds (-i5) between each periodic report, so we'll have 5 reports

[root@machine02 ~]# iperf -c machine01 -p 2000 -i5 -t25
------------------------------------------------------------
Client connecting to machine01, TCP port 2000
TCP window size: 23.2 KByte (default)
------------------------------------------------------------
[ 3] local 10.195.196.18 port 45284 connected with 10.195.196.48 port 2000
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 5.0 sec 3.04 GBytes 5.22 Gbits/sec
[ ID] Interval Transfer Bandwidth
[ 3] 5.0-10.0 sec 3.37 GBytes 5.80 Gbits/sec
[ ID] Interval Transfer Bandwidth
[ 3] 10.0-15.0 sec 3.34 GBytes 5.73 Gbits/sec
[ ID] Interval Transfer Bandwidth
[ 3] 15.0-20.0 sec 3.34 GBytes 5.74 Gbits/sec
[ ID] Interval Transfer Bandwidth
[ 3] 20.0-25.0 sec 3.13 GBytes 5.38 Gbits/sec
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-25.0 sec 16.2 GBytes 5.58 Gbits/sec


or simply send 10GB over the network :

[root@machine02 ~]# iperf -c machine01 -p 2000 -n 10000M
------------------------------------------------------------
Client connecting to machine01, TCP port 2000
TCP window size: 23.2 KByte (default)
------------------------------------------------------------
[ 3] local 10.195.196.18 port 45619 connected with 10.195.196.48 port 2000
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-15.4 sec 9.77 GBytes 5.44 Gbits/sec