[LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Amit Kucheria]

Hi all,

Sally Floyd's Link sharing paper defines the following:

1. Bounded class: class that is not allowed to borrow from ancestor 
classes, regardless of the limit status of those classes.

2. Isolated class: class that does not allow non-descendant classes to 
borrow its unused bandwidth and that does not borrow bandwidth from 
other classes in turn

How does HTB implement a 'bounded class'? I seem to see no constructs to 
be able to do this.

The 'ceil' parameter allows us to implement a part of the 'isolated'
definition above. By setting it equal to 'rate', the class does not
borrow bandwidth, but what will stop other classes from borrowing its
unused bandwidth?

Regards,
Amit

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                  Amit Kucheria
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Re: [LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Stef Coene]

On Friday 16 August 2002 23:09, Amit Kucheria wrote:
> Hi all,
>
> Sally Floyd's Link sharing paper defines the following:
>
> 1. Bounded class: class that is not allowed to borrow from ancestor
> classes, regardless of the limit status of those classes.
>
> 2. Isolated class: class that does not allow non-descendant classes to
> borrow its unused bandwidth and that does not borrow bandwidth from
> other classes in turn
> How does HTB implement a 'bounded class'? I seem to see no constructs to
> be able to do this.
You can use the ceil parameter to bound a class to a certain rate.  With rate 
 = ceil, you will get the same result as the bounded option in cbq.

> The 'ceil' parameter allows us to implement a part of the 'isolated'
> definition above. By setting it equal to 'rate', the class does not
> borrow bandwidth, but what will stop other classes from borrowing its
> unused bandwidth?
Providing no ceil parameter means rate = ceil.  But this can not be used to 
implement isolated like in cbq.  Rate = ceil means the class can not use more 
bandwidth then it's rate.  Isolated in cbq means other classes can not borrow 
bandwidth from the class and that's not the same.  There is no way you can 
implement isolated with htb.  

But with htb you can do something like this :

Total : 100
class1   rate 20   ceil 20
class2   rate 40   ceil 80
class3   rate 40   ceil 80

class 1 is isolated like in cbq.  It can not use more then it's rate/ceil and 
class2 and class3 will never use bandwidth from class1, only from each other. 
 Just like the definition of isolated :)

Stef

Btw, I never could get isolated working with cbq.

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Re: [LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Amit Kucheria]

On Fri, 16 Aug 2002, Stef Coene wrote:

>> The 'ceil' parameter allows us to implement a part of the 'isolated'
>> definition above. By setting it equal to 'rate', the class does not
>> borrow bandwidth, but what will stop other classes from borrowing its
>> unused bandwidth?
>
> Providing no ceil parameter means rate = ceil.  But this can not be
> used to implement isolated like in cbq. Rate = ceil means the class
> can not use more bandwidth then it's rate. Isolated in cbq means other
> classes can not borrow bandwidth from the class and that's not the
> same.  There is no way you can implement isolated with htb.
>
> But with htb you can do something like this :
>
> Total : 100
> class1   rate 20   ceil 20
> class2   rate 40   ceil 80
> class3   rate 40   ceil 80
>
> class 1 is isolated like in cbq. It can not use more then it's
> rate/ceil and class2 and class3 will never use bandwidth from class1,
> only from each other. Just like the definition of isolated :)

What happens when there is no traffic in class 1? Will class 2 and 3 
share class 1's bandwidth then?

The reason I am asking these questions is because I am trying to see if 
HTB can be used in place of CBQ in Diffserv. Has anybody tried something 
like this?

Regards,
Amit

-- 
I'm an angel!!! Honest!
The horns are just there to hold the halo up straight.
^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^
                  Amit Kucheria
          EECS Grad. Research Assistant
         University of Kansas @ Lawrence
   (R): +1-785-830-8521 ||| (C): +1-785-760-2871
____________________________________________________

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Re: [LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Stef Coene]

> > Total : 100
> > class1   rate 20   ceil 20
> > class2   rate 40   ceil 80
> > class3   rate 40   ceil 80
> >
> > class 1 is isolated like in cbq. It can not use more then it's
> > rate/ceil and class2 and class3 will never use bandwidth from class1,
> > only from each other. Just like the definition of isolated :)
>
> What happens when there is no traffic in class 1? Will class 2 and 3
> share class 1's bandwidth then?
No traffic in class 1 means that class2 and class3 will share the same 
bandwidth, but only 80 as maximum.  So the bandwidth of class1 (20) is 
isolated like you can set with cbq.
Htb is straight forward.  Each class will get's his rate as a minimum.  The 
remaining bandwidth is devided according to the rate (and lowest priority 
gets first choice) and this with a maximum of the ceil.

> The reason I am asking these questions is because I am trying to see if
> HTB can be used in place of CBQ in Diffserv. Has anybody tried something
> like this?
I didn't tried, but I think htb will do fine (or even better).

Stef

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Re: [LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Radosław Łoboda]

On Tue, 20 Aug 2002, Amit Kucheria wrote:
> On Fri, 16 Aug 2002, Stef Coene wrote:
> 
> >> The 'ceil' parameter allows us to implement a part of the 'isolated'
> >> definition above. By setting it equal to 'rate', the class does not
> >> borrow bandwidth, but what will stop other classes from borrowing its
> >> unused bandwidth?
> >
> > Providing no ceil parameter means rate = ceil.  But this can not be
> > used to implement isolated like in cbq. Rate = ceil means the class
> > can not use more bandwidth then it's rate. Isolated in cbq means other
> > classes can not borrow bandwidth from the class and that's not the
> > same.  There is no way you can implement isolated with htb.
> >
> > But with htb you can do something like this :
> >
> > Total : 100
> > class1   rate 20   ceil 20
> > class2   rate 40   ceil 80
> > class3   rate 40   ceil 80
> >
> > class 1 is isolated like in cbq. It can not use more then it's
> > rate/ceil and class2 and class3 will never use bandwidth from class1,
> > only from each other. Just like the definition of isolated :)
> 
> What happens when there is no traffic in class 1? Will class 2 and 3 
> share class 1's bandwidth then?
> 
> The reason I am asking these questions is because I am trying to see if 
> HTB can be used in place of CBQ in Diffserv. Has anybody tried something 
> like this?

It works fine for me, although I haven't used CBQ previously so I can't
comapre them. It just works for me, except the delays in interactive class 
are too long, even when the prio is 0 (highest) and the rate and ceil are
maximum. Maybe CBQ is better in reducing the delays... Anybody solved this
problem?

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Re: [LARTC] HTB equivalent for 'bounded' and 'isolated' in CBQ

[Stef Coene]

> It works fine for me, although I haven't used CBQ previously so I can't
> comapre them. It just works for me, except the delays in interactive class
> are too long, even when the prio is 0 (highest) and the rate and ceil are
> maximum. Maybe CBQ is better in reducing the delays... Anybody solved this
> problem?
There is a way with htb to get really low delays.  It can be found on the htb 
homepage (http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm#prio, last 
paragraph).  

Basically, you have 2 classes : on rated to xx% of the link and an other rated 
to 100-X%.  If you make sure you NEVER send more data to the 100-xx% class so 
it never has to ask for more bandwidth, it will have very low delays.  If you 
send more data, the situation is reversed and that class will get very high 
delays.  I still have to test it, but you can use the policer in the filters 
to make sure you never send more data then the rate of the class.


Stef


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