Limiting Network Bandwidth for Testing

Occasionally it's necessary to determine the affects of reduced network bandwidth. Authoring software that works for a networked system backed by Gigabit Ethernet as well as DSL requires testing on both forms of systems.  The alternative is to test on the most capable networking system and then test lower-bandwidth systems on the same network by artificially limiting the bandwidth.

Consulting the all-knowing Google provided a couple general options: trickle and wondershaper.  While there are other utilities, I mainly focused on these two.

Trickle is a 'lightweight user bandwidth shaper', it's particular value is the ability to limit processes independently and it doesn't require superuser privileges.

$ sudo apt-get install trickle

You can limit uploads and downloads to 100 KB/s for a command such as;

$ trickle -u 100 -d 100 wget http://download.blender.org/peach/bigbuckbunny_movies/big_buck_bunny_1080p_stereo.ogg

Independently, you could specify alternative limits for another command.  Trickle is limited to TCP sockets so if you need to limit bandwidth for UDP sockets you'll need to look for an alternative.  Applying system-wide bandwidth, TCP in this case, supposedly is supported via trickled daemon utility but after numerous hours I gave up on getting it to work.  Regardless, I abandoned it's use not only because I couldn't get it to work but also it's limitation to TCP and applying the daemon and client command required prepending 'trickle' to the command line.  This would disqualify applying the network bandwidth constraints to network services like sshd and such without modifying each service starting the process.

Seeking a system-wide bandwidth traffic shaper brought me back to Wondershaper once again.  My first experience with wondershaper I found it didn't always work, this round I tested the usage 1-10 Mbps and I quickly found that it limited the bandwidth like expected until reaching 10 Mbps where it jumped to realized bandwidth of 40 Mbps.  Head-scratcher; working fine for bandwidths under 10Mbps but broke at >= 10Mbps.  Consulting Google again brought me to a fix proposed by 'buzzy'; https://github.com/magnific0/wondershaper/issues/2.  Modifying the wondershaper script as 'buzzy' indicated resolved the issue and I could consistently specify bandwidths 1-40 Mbps and observe realized bandwidths accordingly.

$ cat go

#!/bin/bash



for i in `seq 1 50`; do

  echo "$i Mbps"

  K=`expr $i \* 1024`

  sudo wondershaper wlan0 $K $K

  iperf -t 10 -c 192.168.1.132 2> /dev/null | grep "Mbits/sec"

  sleep 2

done

sudo wondershaper wlan0 clear

$ ./go 

1 Mbps

[  3]  0.0-11.2 sec  1.38 MBytes  1.03 Mbits/sec

2 Mbps

[  3]  0.0-10.7 sec  2.62 MBytes  2.06 Mbits/sec

3 Mbps

[  3]  0.0-10.4 sec  3.75 MBytes  3.02 Mbits/sec

4 Mbps

[  3]  0.0-10.4 sec  5.00 MBytes  4.04 Mbits/sec

5 Mbps

[  3]  0.0-10.5 sec  5.12 MBytes  4.11 Mbits/sec

6 Mbps

[  3]  0.0-10.3 sec  7.38 MBytes  6.00 Mbits/sec

7 Mbps

[  3]  0.0-10.3 sec  8.50 MBytes  6.95 Mbits/sec

8 Mbps

[  3]  0.0-10.3 sec  9.75 MBytes  7.97 Mbits/sec

9 Mbps

[  3]  0.0-10.2 sec  10.6 MBytes  8.76 Mbits/sec

10 Mbps

[  3]  0.0-10.1 sec  12.0 MBytes  9.94 Mbits/sec

11 Mbps

[  3]  0.0-10.1 sec  13.2 MBytes  11.0 Mbits/sec

12 Mbps

[  3]  0.0-10.2 sec  14.5 MBytes  12.0 Mbits/sec

13 Mbps

[  3]  0.0-10.2 sec  15.5 MBytes  12.8 Mbits/sec

14 Mbps

[  3]  0.0-10.3 sec  16.1 MBytes  13.2 Mbits/sec

15 Mbps

[  3]  0.0-10.1 sec  16.4 MBytes  13.6 Mbits/sec

16 Mbps

[  3]  0.0-10.1 sec  19.0 MBytes  15.8 Mbits/sec

17 Mbps

[  3]  0.0-10.1 sec  19.8 MBytes  16.4 Mbits/sec

18 Mbps

[  3]  0.0-10.1 sec  21.1 MBytes  17.6 Mbits/sec

19 Mbps

[  3]  0.0-10.1 sec  22.1 MBytes  18.3 Mbits/sec

20 Mbps

[  3]  0.0-10.1 sec  23.1 MBytes  19.3 Mbits/sec

...

While the use of WonderShaper requires superuser privileges, it limits the system network bandwidth in it's entirety. Enjoy.