IPERF.md

Guide: iperf

IPerf is a CLI tool that determines the bandwidth between 2 points in a network. Unlike the other tools recommended in SCC365, it requires commands to be executed on both nodes for a single test.

Iperf can be used with the command "iperf3" followed by any flags.

• -s: Specify that the instance is to act as the server node
• -c: Specify that the instance is to act as the client node connecting to a given server
• -p: The port number to listen/connect to

The following flags can be used alongside the -c flag:

• -u: Opt for testing with UDP rather than the default that is TCP
• -t: Time to run the test for (in seconds)
• -P: Number of simultaneous streams to test over (useful for testing multiple path routes)

📖 There is more iperf3 can do, see the iperf3 man page for more!

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Example: Testing Bandwidth

• Firstly, run an iperf server on one of the nodes. For example, on a machine with the publically visible IP 10.50.50.30:

  iper3 -s -p 5201

• Next to run the test, on the other machine run an iperf client that connects to prior created server:

  iperf -c 10.50.50.30 -p 5201 -t 5

  This command will run an iperf test over TCP for 5 seconds, determining the bandwidth between the client and 10.50.50.30
• The output from on client then might look somewhat like:

  Connecting to host 10.50.50.30, port 5201
  [  4] local 10.0.0.2 port 50628 connected to 10.50.50.30 port 5201
  [ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
  [  4]   0.00-1.00   sec  4.94 MBytes  41.4 Mbits/sec    0    495 KBytes       
  [  4]   1.00-2.00   sec  4.73 MBytes  39.6 Mbits/sec    0    684 KBytes       
  [  4]   2.00-3.00   sec  4.22 MBytes  35.4 Mbits/sec    0    857 KBytes       
  [  4]   3.00-4.00   sec  5.00 MBytes  41.9 Mbits/sec    0   1.04 MBytes       
  [  4]   4.00-5.00   sec  5.00 MBytes  41.9 Mbits/sec    0   1.24 MBytes       
  - - - - - - - - - - - - - - - - - - - - - - - - -
  [ ID] Interval           Transfer     Bandwidth       Retr
  [  4]   0.00-5.00   sec  23.9 MBytes  40.1 Mbits/sec    0             sender
  [  4]   0.00-5.00   sec  18.5 MBytes  31.1 Mbits/sec                  receiver
  

  The summary at the bottom of the output contains the most useful information.
  • The sender line shows that the upload speed from the iperf client to the server is 40.1Mbps
  • The receiver line shows that the download speed from the iperf server to the client is 31.1Mbps

Example: Testing Bandwidth in Mininet

Using iperf in Mininet can be easily done though the command given in the Mininet prompt like so:

• The Mininet prompt provides an iperf command that can be very easily used to test the bandwidth between 2 nodes. For example, to test the bandwidth between h1 and h2, the following command can be executed:

  mininet> iperf h1 h2

This however does not have the configurability of using the iperf3 command recommended. Unfortunately, without using ssh or xterm, there isn't a straight forward way to be running commands on 2 Mininet hosts at the same time (exactly what is needed to run both an iperf server and client)! To do this, you have to be able to have the server application run in the background like so:

• To repeat the h1 to h2 iperf test done above, you can use the node name prefixing to run the iperf3 command:

  mininet> h1 iperf3 -s -p 5201 &
  

  Adding the & to the end of the command lets the shell continue immediately, effectively putting the command in the background. This is not just a feature in the Mininet prompt, but is in most shell environments you'll use (thanks to bash).

  This starts an iperf server in the background on h1. You can check this by checking the jobs on h1 like so:

  mininet> h1 jobs
  

• Next, you need to run the client on h2 and connect to the server that is running on h1:

  mininet> h2 iperf3 -c h1 -p 5201 -t 5
  

  Then the test should execute, and the client side results should be displayed

• Finally, to clean up the iperf3 server should by terminated. Using the job ID (in the square brackets [X]), run the kill command on h1:

  mininet> h1 kill %1
  

  (assuming the job ID was 1)

Example: Parallel Streams

An IPerf test will appear to devices in the network as a single "flow". So, when testing the bandwidth between 2 nodes that have multiple load balanced routes, the -P flag should be used on the client.

• Simply running the same command as in the prior examples for the server is okay (using the setup from the first example):

  iper3 -s -p 5201
  

• However, for the client, the -P flag should be used to indicate how many streams should be used. Each stream will present itself as a separate flow. It is worth noting that the load balancing algorithm may bin multiple flows down the same path. For example, the use 5 parallel streams:

  iperf -c 10.50.50.30 -p 5201 -P 5