HTB overlimits traffic BW

Question

I am using TC Linux HTB to limit traffic bandwidths in the egress interface.

For it, I've set the following instructions on a linux container:

tc qdisc add dev eth2 root handle 1: htb default 12 
tc class add dev eth2 parent 1: classid 1:1 htb rate 100mbit ceil 100mbit 
tc class add dev eth2 parent 1:1 classid 1:10 htb rate 40mbit ceil 100mbit  
tc class add dev eth2 parent 1:1 classid 1:12 htb rate 1bps ceil 100mbit

Without configure any filter, when I realize an iperf3 with a throughput of 200M that passes the container, the traffic goes through the default queue (12). However, instead of having 100 Mbps as set, I obtained 73-75 Mbps.

Why this can occur?

Answer 1

If HTB is overlimiting traffic bandwidth, it means that the allocated bandwidth for a particular class or queue is insufficient to handle the incoming traffic. This issue can be addressed by adjusting the HTB configuration to allocate more bandwidth or prioritize critical traffic. https://serverfault.com/questions/254535/traffic-shaping-on-linux-with-htb-weird-results

Answer 2

Well, it seems that "1bps" does not work very well, changing it to "8bit" works better. Also, it is important to note that these instructions were applied over a virtual machine and it works better on local.