lartc.org : Linux Advanced Routing & Traffic Control
(Answer) (Category) lartc.org FAQ : (Category) HTB remarks :
Low delays with HTB
If you want really low delays for a class, you have to give the class a rate that's higher then the bandwidth it uses so it will never be overlimit. And you have to give it the highest priority (lowest prio parameter).

If the class gets overlimit, all not-overlimited classes (so basically all other classes) will be served first and the delay will increase.

The default qdisc added to a htb class is pfifo_fast qdisc. The size of the qdisc is the device queue length and this is 100 packets for an ethernet device. So if you want to have a shorter queue, you have to add a shorter qdisc to the htb qdisc. The longer the queue, the longer a packet can sit in the queue, the longer the delay can be.
stef.coene@docum.org

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