How to Limit the Network Bandwidth Used by Applications in a Linux System with Trickle
Example 3: Uploading a 19 MB mp4 file to our FTP server using with and without trickle.
In this example we will use the freely-distributable “He is the gift” video, available for download from this link.
We will initially download this file to your current working directory with the following command:
# wget http://media2.ldscdn.org/assets/missionary/our-people-2014/2014-00-1460-he-is-the-gift-360p-eng.mp4
First off, we will start the trickled daemon with the command listed above:
# trickled -d 30 -u 10
# ncftpput -u username -p password 192.168.0.15 /testdir 2014-00-1460-he-is-the-gift-360p-eng.mp4
2014-00-1460-he-is-the-gift-360p-eng.mp4: 18.53 MB 36.31 MB/s
# trickle ncftpput -u username -p password 192.168.0.15 /testdir 2014-00-1460-he-is-the-gift-360p-eng.mp4
2014-00-1460-he-is-the-gift-360p-eng.mp4: 18.53 MB 9.51 kB/s
As we can see in the output above, the upload transfer rate dropped to ~10 KB/s.
Example 4: Downloading the same video with and without trickle
As in Example 2, we will be downloading the file to the current working directory.
# ncftpget -u username -p password 192.168.0.15 . /testdir/2014-00-1460-he-is-the-gift-360p-eng.mp4
2014-00-1460-he-is-the-gift-360p-eng.mp4: 18.53 MB 108.34 MB/s
# trickle ncftpget -u username -p password 18.104.22.168 . /testdir/2014-00-1460-he-is-the-gift-360p-eng.mp4
2014-00-1460-he-is-the-gift-360p-eng.mp4: 18.53 MB 29.28 kB/s
Which is in accordance with the download limit set earlier (30 KB/s).
Note: That once the daemon has been started, there is no need to set individual limits for each application that uses trickle.
As we mentioned earlier, one can further customize trickle’s bandwidth shaping through trickled.conf. A typical section in this file consists of the following:
[service] Priority = <value> Time-Smoothing = <value> Length-Smoothing = <value>
- [service] indicates the name of the application whose bandwidth usage we intend to shape.
- Priority allows us to specify a service to have a higher priority relative to another, thus not allowing a single application to hog all the bandwidth which the daemon is managing. The lower the number, the more bandwidth that is assigned to [service].
- Time-Smoothing [in seconds]: defines with what time intervals trickled will try to let the application transfer and / or receive data. Smaller values (something between the range of 0.1 – 1s) are ideal for interactive applications and will result in a more continuous (smooth) session while slightly larger values (1 – 10 s) are better for applications that need bulk transfer. If no value is specified, the default (5 s) is used.
- Length-Smoothing [in KB]: the idea is the same as in Time-Smoothing, but based on the length of an I/O operation. If no value is specified, the default (10 KB) is used.
Changing the smoothing values will translate into the application specified by [service] using transfer rates within an interval instead of a fixed value. Unfortunately, there is no formula to calculate the lower and upper limits of this interval as it mainly depends of each specific case scenario.
The following is a trickled.conf sample file in the CentOS 7 client (192.168.0.17):
[ssh] Priority = 1 Time-Smoothing = 0.1 Length-Smoothing = 2 [ftp] Priority = 2 Time-Smoothing = 1 Length-Smoothing = 3
Using this setup, trickled will prioritize SSH connections over FTP transfers. Note that an interactive process, such as SSH, uses smaller time-smoothing values, whereas a service that performs bulk data transfers (FTP) uses a greater value. The smoothing values are responsible for the download and upload speeds in our previous example not matching the exact value specified by the trickled daemon but moving in an interval close to it.
In this article we have explored how to limit the bandwidth used by applications using trickle on Fedora-based distributions and Debian / derivatives. Other possible use cases include, but are not limited to:
- Limiting the download speed via a system utility such as wget, or a torrent client, for example.
- Limiting the speed at which your system can be updated via `yum` (or `aptitude`, if you’re in a Debian-based system), the package management system.
- If your server happens to be behind a proxy or firewall (or is the proxy or firewall itself), you can use trickle to set limits on both the download and upload, or communication speed with the clients or the outside.
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