[LARTC] Prio and latency with HTB Classes

[LARTC] Prio and latency with HTB Classes

[GoMi]

 
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Sorry if you have already answered this question, but i have a big mess right now.. I red the lartg FAQ and it literally says:

"If you have 2 htb classes with different prio parameters, the class with the lowest prio parameter gets all the remaining bandwidth from the parent (after the other class has received its rate). The class with the lowest parameter will also the class with the lowest latency. However, if this class is overlimited (there is more traffic then the configured rate), the latency can go up. "


I have to classes, and i have interactive traffic and non-interactive traffic, each assigned to one of these classes.

When i get lots of tcp connections to the non-interactive and it begins to ceil, then it seems not to lend that bw again whenever the interactive-class needs it. They are configured like this:

tc class add dev ${DEV} parent 1:1 classid 1:10 htb prio 1 rate 200kbit ceil 300kbit
tc class add dev ${DEV} parent 1:1 classid 1:20 htb prio 2 rate 100kbit ceil 300kbit


I dont understand this " However, if this class is overlimited (there is more traffic then the configured rate), the latency can go up. " <-- What should i do? Which prio should i set, so that interactive traffic class has low latency and has the highest prio?

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Re: [LARTC] Prio and latency with HTB Classes

[Stef Coene]

On Sunday 25 May 2003 18:46, GoMi wrote:
> Sorry if you have already answered this question, but i have a big mess
> right now.. I red the lartg FAQ and it literally says:
>
> "If you have 2 htb classes with different prio parameters, the class with
> the lowest prio parameter gets all the remaining bandwidth from the parent
> (after the other class has received its rate). The class with the lowest
> parameter will also the class with the lowest latency. However, if this
> class is overlimited (there is more traffic then the configured rate), the
> latency can go up. "
>
>
> I have to classes, and i have interactive traffic and non-interactive
> traffic, each assigned to one of these classes.
>
> When i get lots of tcp connections to the non-interactive and it begins to
> ceil, then it seems not to lend that bw again whenever the
> interactive-class needs it. They are configured like this:
It can take some time before the non-interactive traffic will slow down if you 
generate interactive traffic.  You can prevent this by ceiling the 
non-interactive traffic so there is always some minimal bandwidth left for 
the interactive traffic.

> tc class add dev ${DEV} parent 1:1 classid 1:10 htb prio 1 rate 200kbit
> ceil 300kbit
> tc class add dev ${DEV} parent 1:1 classid 1:20 htb prio 2 rate 100kbit
> ceil 300kbit
>
>
> I dont understand this " However, if this class is overlimited (there is
> more traffic then the configured rate), the latency can go up. " <-- What
> should i do? Which prio should i set, so that interactive traffic class has
> low latency and has the highest prio?
You have to create a low prio class for your interactive class with rate = 
maximum traffic that you ever expect in that class.  If you send more data in 
the class, the latency will go up.  Example :
class 1, rate 50 kbit
  class 10, prio 1, rate 10 kbit
  class 11, prio 2, rate 10 kbit
  class 12, prio 2, rate 80 kbit

If class 10 is sending less then 10kbit, the latency will be low.  But if that 
class sends more then 10kbit, the latency will go up.  You can prevent this 
by using policers in your filters so you can control how many packets are 
sended to class 10.

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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