On Sunday 18 May 2003 19:18, Martin A. Brown wrote:
> Maybe this is just for Stef?
>
> In answering Miernik's question (which Stef already answered), I read
> this:
>
> http://www.docum.org/stef.coene/qos/faq/cache/13.html
>
> I thought it didn't matter what the rate was in a parent class? I thought
> that it only mattered what the ceil was in a parent class. I'm doubting
> myself now that I read this FAQ answer.
>
> My understanding:
>
> The parent class is only consulted by the child class when the child
> class has exceeded its rate and wants to borrow from the parent. So,
> the parent class rate is not consulted, but the ceil is used to
> determine whether or not to lend?
>
> Is my understanding wrong?
>
> What's the story!?
Take this example :
tc class add dev eth0 classid 1:1 parent 1:0 htb rate 200kbps ceil 50kbps
tc class add dev eth0 classid 1:10 parent 1:1 htb rate 150kbps ceil 128kbps
tc class add dev eth0 classid 1:20 parent 1:1 htb rate 150kbps ceil 128kbps
Both classes will get 150kbps. So no parent ceil/rate is checked/respected.
I also did some tests to find out how the parent rate is used to split the
traffic to child classes. Example :
tc class add dev eth0 classid 1:1 parent 1:0 htb rate 200kbps
tc class add dev eth0 classid 1:10 parent 1:1 htb rate 150kbps ceil 200kbps
tc class add dev eth0 classid 1:20 parent 1:1 htb rate 50kbps ceil 200kbps
tc class add dev eth0 classid 1:100 parent 1:10 htb rate 50kbps ceil 200kbps
tc class add dev eth0 classid 1:200 parent 1:20 htb rate 50kbps ceil 200kbps
And this results is 75% for class 1:10.
But
tc class add dev eth0 classid 1:1 parent 1:0 htb rate 200kbps
tc class add dev eth0 classid 1:10 parent 1:1 htb rate 150kbps ceil 200kbps
tc class add dev eth0 classid 1:20 parent 1:1 htb rate 50kbps ceil 200kbps
tc class add dev eth0 classid 1:100 parent 1:10 htb rate 80kbps ceil 200kbps
tc class add dev eth0 classid 1:200 parent 1:20 htb rate 80kbps ceil 200kbps
gives 65% to class 1:100.
So it's not clear to me how the rate of the parent is used in the
calculations. It is, but I don't know how.
For the ceil :
tc class add dev eth0 classid 1:1 parent 1:0 htb rate 100kbps
tc class add dev eth0 classid 1:10 parent 1:1 htb rate 150kbps ceil 100kbps
tc class add dev eth0 classid 1:20 parent 1:1 htb rate 50kbps ceil 100kbps
tc class add dev eth0 classid 1:100 parent 1:10 htb rate 20kbps ceil 200kbps
tc class add dev eth0 classid 1:200 parent 1:20 htb rate 20kbps ceil 200kbps
Total bandwidth is 200kbps. So the 100kbps ceil is never respected.
Stef
--
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