[LARTC] Problem while using HTB bandwidth limitation

[LARTC] Problem while using HTB bandwidth limitation

[Nimit Gupta]

Hello everyone,

I am using htb to shape bandwidth but I can see heavy ups and downs from 
the specified limit. I have seen users with 24Kbit limitation can reach 
upto 36Kbit.

Can there be any problem if I set 10 classes each restricted to 24kbit 
under a class which has been restricted to 128Kbit.

My point is what happens if total of child classes, is more than the 
parent class itself. Does it distribute fairly ie equally to all 10 
classes or will there be a problem.

I want it to be this way because I know not all 10 people use it 
simultaneously there can be 7 people at max who will be browsing at same 
time.

Here are some rules:

#Creating root qdisc
tc qdisc add dev eth0 root handle 1: htb default 4000

tc c a dev eth0 parent 1: classid 1:1 htb rate 192Kbit burst 15Kbit

#Rules for default class
tc c a dev eth0 parent 1:1 classid 1:4000 htb rate 16Kbit burst 10Kbit
tc q a dev eth0 parent 1:4000 handle 4000: sfq perturb 10

# Rules for each of the 10 machines
tc c a dev eth0 parent 1:1 classid 1:$C_ID htb rate 24Kbit burst 10Kbit 

tc q a dev eth0 parent 1:$C_ID handle $C_ID: sfq perturb 10
tc f a dev eth0 protocol ip parent 1: prio 5 u32 match ip dst $IP 
classid 1:$C_ID


With regards,
Nimit

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Stef Coene]

On Monday 01 September 2003 15:02, Nimit Gupta wrote:
> Hello everyone,
>
> I am using htb to shape bandwidth but I can see heavy ups and downs from
> the specified limit. I have seen users with 24Kbit limitation can reach
> upto 36Kbit.
>
> Can there be any problem if I set 10 classes each restricted to 24kbit
> under a class which has been restricted to 128Kbit.
>
> My point is what happens if total of child classes, is more than the
> parent class itself. Does it distribute fairly ie equally to all 10
> classes or will there be a problem.
Each class should be able to het 1/10 of 128kbit.  But it can be bursty.

> I want it to be this way because I know not all 10 people use it
> simultaneously there can be 7 people at max who will be browsing at same
> time.
>
> Here are some rules:
>
> #Creating root qdisc
> tc qdisc add dev eth0 root handle 1: htb default 4000
>
> tc c a dev eth0 parent 1: classid 1:1 htb rate 192Kbit burst 15Kbit
>
> #Rules for default class
> tc c a dev eth0 parent 1:1 classid 1:4000 htb rate 16Kbit burst 10Kbit
> tc q a dev eth0 parent 1:4000 handle 4000: sfq perturb 10
>
> # Rules for each of the 10 machines
> tc c a dev eth0 parent 1:1 classid 1:$C_ID htb rate 24Kbit burst 10Kbit
>
> tc q a dev eth0 parent 1:$C_ID handle $C_ID: sfq perturb 10
> tc f a dev eth0 protocol ip parent 1: prio 5 u32 match ip dst $IP
> classid 1:$C_ID
Try to remove the burst parameter.  And if you have a 192Kbit link, you should 
limit all bandwidth to 188kbit so YOU are the bottleneck on the link and not 
the modem.

Stef

-- 

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

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Martin A. Brown]

Hi there Nimit,

 : >>Can there be any problem if I set 10 classes each restricted to 24kbit
 : >>under a class which has been restricted to 128Kbit.
 : >>
 : >>My point is what happens if total of child classes, is more than the
 : >>parent class itself. Does it distribute fairly ie equally to all 10
 : >>classes or will there be a problem.
 : >
 : > Each class should be able to het 1/10 of 128kbit.  But it can be bursty.
 :
 : It can burst to some extent but I could see the rate going more than
 : double in some cases why is it so?

In HTB, all shaping happens in the leaf classes.  For ease on the CPU (and
apparently, the difficulty of the algorithm), HTB is designed to believe
you when you say that each of your 10 leaf classes should get 24kbit, and
it does not check the parent class to make sure the parent class is
throttling all of the children.

You had used a 24kbit rate and no specified ceiling on each of these 10
classes.  This means that you have the equivalent of 24kbit rate and
24kbit ceil.  You are guaranteeing 24kbit at all times to every class!
You might end up sending up to 240kbit (not accounting for your burst
setting either).

In order to approach better your 192kbit line with 10 classes, I would
recommend trying a configuration more like this.  Use a rate 16kbit and
ceil 24kbit for each of your classes.  This means that a leaf class will
consult the parent class for leftover bandwidth above 16kbit.  And above
24kbit, it will cease asking the parent to borrow bandwidth.

This means that all of your classes would send a maximum of 160kbit of
guaranteed traffic before consulting the parent class which has a
bandwidth to divide amongst the children.

 : Yes, now I have removed the burst parameter but can you explain me why
 : to limit all bandwidth to 188 when I have 192, I am having DSL
 : connection.

It is immaterial what sort of connection (speed) you have.  The key (and
secret) is that you must be the bottleneck.  In order for you to control
latency and bandwidth use, you must ensure that you are the slowest point.
Annoyingly, the only successful way to identify exactly what speed to use
as a bandwidth cap is experimentation.  A good general suggestion is to
lop off a couple of kbit and try capping your bandwidth exactly as Stef
suggests.  Try using 188kbit, and see if your apparent control increases.

Best of luck,

-Martin

-- 
Martin A. Brown --- SecurePipe, Inc. --- mabrown@securepipe.com

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Nimit Gupta]

Hello,
Thanks for the reply, but still have few doubts.


> On Monday 01 September 2003 15:02, Nimit Gupta wrote:
> 
>>Hello everyone,
>>
>>I am using htb to shape bandwidth but I can see heavy ups and downs from
>>the specified limit. I have seen users with 24Kbit limitation can reach
>>upto 36Kbit.
>>
>>Can there be any problem if I set 10 classes each restricted to 24kbit
>>under a class which has been restricted to 128Kbit.
>>
>>My point is what happens if total of child classes, is more than the
>>parent class itself. Does it distribute fairly ie equally to all 10
>>classes or will there be a problem.
> 
> Each class should be able to het 1/10 of 128kbit.  But it can be bursty.

It can burst to some extent but I could see the rate going more than 
double in some cases why is it so?

> 
> 
>>I want it to be this way because I know not all 10 people use it
>>simultaneously there can be 7 people at max who will be browsing at same
>>time.
>>
>>Here are some rules:
>>
>>#Creating root qdisc
>>tc qdisc add dev eth0 root handle 1: htb default 4000
>>
>>tc c a dev eth0 parent 1: classid 1:1 htb rate 192Kbit burst 15Kbit
>>
>>#Rules for default class
>>tc c a dev eth0 parent 1:1 classid 1:4000 htb rate 16Kbit burst 10Kbit
>>tc q a dev eth0 parent 1:4000 handle 4000: sfq perturb 10
>>
>># Rules for each of the 10 machines
>>tc c a dev eth0 parent 1:1 classid 1:$C_ID htb rate 24Kbit burst 10Kbit
>>
>>tc q a dev eth0 parent 1:$C_ID handle $C_ID: sfq perturb 10
>>tc f a dev eth0 protocol ip parent 1: prio 5 u32 match ip dst $IP
>>classid 1:$C_ID
> 
> Try to remove the burst parameter.  And if you have a 192Kbit link, you should 
> limit all bandwidth to 188kbit so YOU are the bottleneck on the link and not 
> the modem.

Yes, now I have removed the burst parameter but can you explain me why 
to limit all bandwidth to 188 when I have 192, I am having DSL connection.

with regards,
Nimit

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Nimit Gupta]

Hello,

Thanks a lot Martin & Stef for clarifying my doubts. Your detailed 
explaination was quiet helpful in making the things clear.

I agree that if I give 24Kbit for each leaf class they will get it 
without confirming about the total bandwidth available with the parent 
but why does it allow him to reach upto 48Kbit even when ceiling is 24Kbit?

> In order for you to control
> latency and bandwidth use, you must ensure that you are the slowest point.
> Annoyingly, the only successful way to identify exactly what speed to use
> as a bandwidth cap is experimentation.  A good general suggestion is to
> lop off a couple of kbit and try capping your bandwidth exactly as Stef
> suggests.  Try using 188kbit, and see if your apparent control increases.

Is there a ratio between the total available bandwidth and the amount 
you restrict it to or you can just arbitarily reduce by 5-7 Kbit.

with regards,
Nimit.

Ps: Is there an irc channel for lartc discussion?

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Stef Coene]

On Tuesday 02 September 2003 07:39, Nimit Gupta wrote:
> Hello,
>
> Thanks a lot Martin & Stef for clarifying my doubts. Your detailed
> explaination was quiet helpful in making the things clear.
>
> I agree that if I give 24Kbit for each leaf class they will get it
> without confirming about the total bandwidth available with the parent
> but why does it allow him to reach upto 48Kbit even when ceiling is 24Kbit?
Is this his for a short term, like a burst?

> > In order for you to control
> > latency and bandwidth use, you must ensure that you are the slowest
> > point. Annoyingly, the only successful way to identify exactly what speed
> > to use as a bandwidth cap is experimentation.  A good general suggestion
> > is to lop off a couple of kbit and try capping your bandwidth exactly as
> > Stef suggests.  Try using 188kbit, and see if your apparent control
> > increases.
>
> Is there a ratio between the total available bandwidth and the amount
> you restrict it to or you can just arbitarily reduce by 5-7 Kbit.
It should be quite accurate.  I tested it for different rates / ceils and each 
time the results where allmost perfect.

Stef

-- 

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

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Nimit Gupta]

Stef Coene wrote:
> On Tuesday 02 September 2003 07:39, Nimit Gupta wrote:
> 
>>Hello,
>>
>>Thanks a lot Martin & Stef for clarifying my doubts. Your detailed
>>explaination was quiet helpful in making the things clear.
>>
>>I agree that if I give 24Kbit for each leaf class they will get it
>>without confirming about the total bandwidth available with the parent
>>but why does it allow him to reach upto 48Kbit even when ceiling is 24Kbit?
> 
> Is this his for a short term, like a burst?

Yeah its for a short period but it keeps happening, I mean it will reach 
to 48Kbit and then after few sec it will stablize at 24Kbit then again 
it will reach to 48 and this repeats.

can you explain how to calculate burst rates for better control and 
accuracy?


>>>In order for you to control
>>>latency and bandwidth use, you must ensure that you are the slowest
>>>point. Annoyingly, the only successful way to identify exactly what speed
>>>to use as a bandwidth cap is experimentation.  A good general suggestion
>>>is to lop off a couple of kbit and try capping your bandwidth exactly as
>>>Stef suggests.  Try using 188kbit, and see if your apparent control
>>>increases.
>>
>>Is there a ratio between the total available bandwidth and the amount
>>you restrict it to or you can just arbitarily reduce by 5-7 Kbit.
> 
> It should be quite accurate.  I tested it for different rates / ceils and each 
> time the results where allmost perfect.

So I want to know what ratio it is as you said for 192Kbit make 188Kbit 
thats equivalent to 2 percent, is this the way.

One more thing, Is there something like isolated(as in cbq) in htb, that 
is irrespective of others demand the bandwidth allocated to someone as 
isolated does not get affected.

Is there an irc channel for lartc discussions?

with regards,
Nimit

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Re: [LARTC] Problem while using HTB bandwidth limitation

[Stef Coene]

On Wednesday 03 September 2003 06:59, Nimit Gupta wrote:
> Yeah its for a short period but it keeps happening, I mean it will reach
> to 48Kbit and then after few sec it will stablize at 24Kbit then again
> it will reach to 48 and this repeats.
>
> can you explain how to calculate burst rates for better control and
> accuracy?
Mhh.  How long is it stayig at 48Kbit?  Can you plot it?

> >>>In order for you to control
> >>>latency and bandwidth use, you must ensure that you are the slowest
> >>>point. Annoyingly, the only successful way to identify exactly what
> >>> speed to use as a bandwidth cap is experimentation.  A good general
> >>> suggestion is to lop off a couple of kbit and try capping your
> >>> bandwidth exactly as Stef suggests.  Try using 188kbit, and see if your
> >>> apparent control increases.
> >>
> >>Is there a ratio between the total available bandwidth and the amount
> >>you restrict it to or you can just arbitarily reduce by 5-7 Kbit.
> >
> > It should be quite accurate.  I tested it for different rates / ceils and
> > each time the results where allmost perfect.
>
> So I want to know what ratio it is as you said for 192Kbit make 188Kbit
> thats equivalent to 2 percent, is this the way.
It's not so easy to tell.  Sometimes, people lower the total bandwidth and 
suddenly the shaping is working.

> One more thing, Is there something like isolated(as in cbq) in htb, that
> is irrespective of others demand the bandwidth allocated to someone as
> isolated does not get affected.
Isolated is not working in cbq.  And no, there is no such option in htb.

> Is there an irc channel for lartc discussions?
Yes, #lartc @ irc.oftc.net.  But you have to be lucky to find someone not-away 
:)

Stef

-- 

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

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