[LARTC] questiona about CBQ algorithm in Linux

[LARTC] questiona about CBQ algorithm in Linux

[yuxiao]

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Hi Stef and Alexey


I have read some documents about CBQ algorithm from http://www.icir.org/floyd/cbq.html
but still have some question about CBQ in Linux
.
1. First estimator can estimate how much bandwidth already USED per class. one estimating algorithm is EWMA (exponential weighted moving average), how about  Linux implemenatation about estimator? 
also do you have link for this algorithm? I canot find it.

2. If I want to see how CBQ work in Linux,  any suggestion how I start read these code?
there are a lot of files under tc folder, q_cbq.c tc_cbq.c...

3. In linux how CBQ measure used bandwidth per class? does it measure
bandwith bits/sec? If it measue bandwidth every seconds, is there any way to
collect these data (grap these data)? 

4. I read stef's monitor.pl, it is based on firwall code. why didn't use CBQ's measurement result if it can do (I am not sure..)?

5. In stef's bandwidth monitor, I am not sure whether  it is per-flow based or per-class based. if it is per-flowed based, how can I modify to per-class? I belivee CBQ can estimate used bandwidth PER CLASS.
For example  you have two flow belong to one class.

6. In Linux how CBQ distribute the excess bandwidth between sibling class
when "borrow" enabled.  what algorithm it used? which code?

7. Can HTB do the same job as CBQ right now, can HTB do borrow ? 


Thanks in advance


best regards


yuxiao Jia



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Re: [LARTC] questiona about CBQ algorithm in Linux

[Stef Coene]

> 4. I read stef's monitor.pl, it is based on firwall code. why didn't use
> CBQ's measurement result if it can do (I am not sure..)?
With iptables you can monitor everything you want.  It can also be used to 
determine who is using the most bandwidth.  Actually it's a bandwidth monitor 
and not a tc monitor.  But I use it to monitor tc :).
I have some other scripts that uses the counters in cbq if you are intersted 
(see the page under the gui link).  They create nice looking graphs.  So ne 
real-time measurement like monitor.pl.

> 5. In stef's bandwidth monitor, I am not sure whether  it is per-flow based
> or per-class based. if it is per-flowed based, how can I modify to
> per-class? I belivee CBQ can estimate used bandwidth PER CLASS. For example
>  you have two flow belong to one class.
Again, you can montir whatever you want with monitor.pl as long as you can 
match the packets with iptables.  There are other monitors (I just don't 
remember them right now), who can identify flows and monitor them.  

> 6. In Linux how CBQ distribute the excess bandwidth between sibling class
> when "borrow" enabled.  what algorithm it used? which code?
>
> 7. Can HTB do the same job as CBQ right now, can HTB do borrow ?
Yes :
class 1 with rate = 100, ceil = 100
   class 11 with rate = 25, ceil = 100
   class 12 with rate = 75, ceil = 100
Class 11 and 12 borrow the same 100.  Class 12 will get 75% of the link, class 
11 15%.

Stef
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