How to simulate latency on Linux

Some people asked me (… well, only one person) how was it possible to add latency between hosts in one of my previous articles about the effects of latency on throughput. When I decided to write the article, my searches led me to tc: Adding Simulated Network Latency To Your Linux Server. Of the different options available, this looked like the best one since there was no need to use a middlebox between the hosts.

How does it work? Continue reading

The Effects of Latency on Throughput

I still remember 2009 when I was assigned the task to validate a satellite internet link with 16Mbps bandwidth. At that time that was a looooot in my country.

My biggest surprise was that no matter how many speedtests and download tests I did, I simply couldn’t reach the full 16Mbps and saturate the link. And there I went to complain with the service provider.

All this happened until a very patient young engineer explained it to me:

Mário, it is a satellite link. Latency is too high, you have to make many simultaneous downloads or use a download accelerator.

And it was there that, for the first time, I learned that high latency links like those satellite links (ping latencies of ~500-600ms) influence not only voice/video real-time communication but it also influences throughput… the “speed”.

Let’s verify that…

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