[LARTC] HTB and theory

[LARTC] HTB and theory

[Catalin Bucur]

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Hello,

Let's say that my ISP gives me 5000Kbit guaranteed bandwidth. I'm
starting a HTB traffic shape like this:

tc qdisc add dev eth1 root handle 11: htb  default 99
tc class add dev eth1 parent 11:0 classid 11:1 htb rate 10000Kbit burst
ceil 10000Kbit prio 0
tc class add dev eth1 parent 11:1 classid 11:2 htb rate 5000Kbit ceil
5000Kbit prio 5
[here I have a lot of sub-classes that borrow from parent 11:2]

I'll let HTB to automatically compute the values for 'burst' and
'cburst'. The problem is elsewhere. What are the correct values for
'rate' and 'ceil' of 11:2 class in this case? In fact, total value of
'ceil's from all sub-classes exceeds 5000Kbit, so there are moments when
the bandwidth that comes from my ISP is bigger than guaranteed bandwidth.
Is there some kind a theory that says how to establish the values of
'rate's and 'ceil's from the parent and its sub-classes?

TIA.
- --
Catalin Bucur      mailto:cata@geniusnet.ro
NOC @ Genius Network SRL - Galati - Romania

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Re: [LARTC] HTB and theory

[Stef Coene]

On Monday 09 December 2002 18:14, Catalin Bucur wrote:
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>
> Hello,
>
> Let's say that my ISP gives me 5000Kbit guaranteed bandwidth. I'm
> starting a HTB traffic shape like this:
>
> tc qdisc add dev eth1 root handle 11: htb  default 99
> tc class add dev eth1 parent 11:0 classid 11:1 htb rate 10000Kbit burst
> ceil 10000Kbit prio 0
> tc class add dev eth1 parent 11:1 classid 11:2 htb rate 5000Kbit ceil
> 5000Kbit prio 5
> [here I have a lot of sub-classes that borrow from parent 11:2]
>
> I'll let HTB to automatically compute the values for 'burst' and
> 'cburst'. The problem is elsewhere. What are the correct values for
> 'rate' and 'ceil' of 11:2 class in this case? In fact, total value of
> 'ceil's from all sub-classes exceeds 5000Kbit, so there are moments when
> the bandwidth that comes from my ISP is bigger than guaranteed bandwidth.
> Is there some kind a theory that says how to establish the values of
> 'rate's and 'ceil's from the parent and its sub-classes?
There are some rules : ceil of child <= ceil of parent, sum (child rates) <= 
rate of parent ....  You don't have to follow this rules, but the final 
shaping result can be strange.
See the faq page on www.docum.org.

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Catalin Bucur]

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Stef Coene wrote:
| On Monday 09 December 2002 18:14, Catalin Bucur wrote:
|
|>Let's say that my ISP gives me 5000Kbit guaranteed bandwidth. I'm
|>starting a HTB traffic shape like this:
|>
|>tc qdisc add dev eth1 root handle 11: htb  default 99
|>tc class add dev eth1 parent 11:0 classid 11:1 htb rate 10000Kbit burst
|>ceil 10000Kbit prio 0
|>tc class add dev eth1 parent 11:1 classid 11:2 htb rate 5000Kbit ceil
|>5000Kbit prio 5
|>[here I have a lot of sub-classes that borrow from parent 11:2]
|>
|>I'll let HTB to automatically compute the values for 'burst' and
|>'cburst'. The problem is elsewhere. What are the correct values for
|>'rate' and 'ceil' of 11:2 class in this case? In fact, total value of
|>'ceil's from all sub-classes exceeds 5000Kbit, so there are moments when
|>the bandwidth that comes from my ISP is bigger than guaranteed bandwidth.
|>Is there some kind a theory that says how to establish the values of
|>'rate's and 'ceil's from the parent and its sub-classes?
|
| There are some rules : ceil of child <= ceil of parent, sum (child
rates) <| rate of parent ....  You don't have to follow this rules, but the final
| shaping result can be strange.
| See the faq page on www.docum.org.
|

I've already seen it :-) But it doesn't say anything like:
sum (child ceils) <= ceil of parent
Is there such a rule?
Am I forced somehow to limit 'rate' of class 11:2 under the guaranteed
value (5000Kbit), but let the 'ceil' equal to this value? It's better to
give the clients let's say 95% of guaranteed bandwidth instead of 100%?

- --
Catalin Bucur      mailto:cata@geniusnet.ro
NOC @ Genius Network SRL - Galati - Romania

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Re: [LARTC] HTB and theory

[Stef Coene]

> | rate of parent ....  You don't have to follow this rules, but the final
> | shaping result can be strange.
> | See the faq page on www.docum.org.
>
> I've already seen it :-) But it doesn't say anything like:
> sum (child ceils) <= ceil of parent
> Is there such a rule?
Yes  : child ceil <= ceil of parent (I just added it to the faq page)

> Am I forced somehow to limit 'rate' of class 11:2 under the guaranteed
> value (5000Kbit), but let the 'ceil' equal to this value? It's better to
> give the clients let's say 95% of guaranteed bandwidth instead of 100%?
You can argument that limit a client to 95% will leave 5% for someone else.  
But I think 100% is a better choice.

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Catalin Bucur]

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Stef Coene wrote:
|
| Yes  : child ceil <= ceil of parent (I just added it to the faq page)
|
| Stef
|

So far, so good. But what if I want to give my clients a little more
bandwidth than (parent ceil) / (no. of clients)?
Let's suppose that I have 10 clients, and guaranteed bandwidth is
5000Kbit. The parent ceil is 5000Kbit, childs' ceils are equal with
500Kbit every each. But I want to give - for example - 800Kbit for each
one, so the parent ceil must be equal or greater than 8000Kbit. That is
the problem, I don't think is a such good ideea to give the parent a
ceil that is greater than guaranteed bandwidth; the result could be
unpredictable.

Thank you for your answers,
- --
Catalin Bucur      mailto:cata@geniusnet.ro
NOC @ Genius Network SRL - Galati - Romania

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Re: [LARTC] HTB and theory

[Abraham van der Merwe]

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Hi Stef!

> > I'll let HTB to automatically compute the values for 'burst' and
> > 'cburst'. The problem is elsewhere. What are the correct values for
> > 'rate' and 'ceil' of 11:2 class in this case? In fact, total value of
> > 'ceil's from all sub-classes exceeds 5000Kbit, so there are moments when
> > the bandwidth that comes from my ISP is bigger than guaranteed bandwidth.
> > Is there some kind a theory that says how to establish the values of
> > 'rate's and 'ceil's from the parent and its sub-classes?
> There are some rules : ceil of child <= ceil of parent, sum (child rates) <= 
> rate of parent ....  You don't have to follow this rules, but the final 
> shaping result can be strange.
> See the faq page on www.docum.org.

What would be nice is if you could document what happens when

     a) child ceil > parent ceil
     b) child rate > parent ceil
     c) child ceil > parent rate
     d) child rate > parent rate

How does this influence the shaping results and the shaping of other
classes? I've actually asked a similar question before: If you have

           1:1
           / \
         /     \
       1:2     1:3
       /|\       \------
     /	|  \       \     \
   1:4 1:5 1:6     1:7   1:8

if 1:7 and 1:8 respects the rate/ceil of 1:3 and 1:3 respects the rate/ceil
of 1:1, but 1:4 does not respect the rate/ceil of 1:2 and 1:2 respects the
rate/ceil of 1:1, does the shaping of 1:3 work as normal and only those
classes under 1:2 are adversely affected or not? from your previous answer,
it seems that the classes under 1:3 would not be affected, but I would love
to know why. what happens with 1:4 requests some bandwidth which 1:2 does
not have...


-- 

Regards
 Abraham

NEWARK has been REZONED!!  DES MOINES has been REZONED!!

___________________________________________________
 Abraham vd Merwe [ZR1BBQ] - Frogfoot Networks
 P.O. Box 3472, Matieland, Stellenbosch, 7602
 Cell: +27 82 565 4451 Http: http://www.frogfoot.net/
 Email: abz@frogfoot.net


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Re: [LARTC] HTB and theory

[Stef Coene]

On Monday 09 December 2002 22:45, Catalin Bucur wrote:
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>
> Stef Coene wrote:
> | Yes  : child ceil <= ceil of parent (I just added it to the faq page)
> |
> | Stef
>
> So far, so good. But what if I want to give my clients a little more
> bandwidth than (parent ceil) / (no. of clients)?
> Let's suppose that I have 10 clients, and guaranteed bandwidth is
> 5000Kbit. The parent ceil is 5000Kbit, childs' ceils are equal with
> 500Kbit every each. But I want to give - for example - 800Kbit for each
> one, so the parent ceil must be equal or greater than 8000Kbit. That is
> the problem, I don't think is a such good ideea to give the parent a
> ceil that is greater than guaranteed bandwidth; the result could be
> unpredictable.
The rule is :
 child ceil <= ceil of parent
So a child with ceil = 800 kbit and a parent with ceil = 5000 kbit is no 
problem.

Or are you speaking about rates :
  sum (rate child ) = rate of parent
You don't have to follow this rule, but it will make things more 
unpredictable.

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Stef Coene]

On Monday 09 December 2002 23:18, Abraham van der Merwe wrote:
> Hi Stef!
>
> > > I'll let HTB to automatically compute the values for 'burst' and
> > > 'cburst'. The problem is elsewhere. What are the correct values for
> > > 'rate' and 'ceil' of 11:2 class in this case? In fact, total value of
> > > 'ceil's from all sub-classes exceeds 5000Kbit, so there are moments
> > > when the bandwidth that comes from my ISP is bigger than guaranteed
> > > bandwidth. Is there some kind a theory that says how to establish the
> > > values of 'rate's and 'ceil's from the parent and its sub-classes?
> >
> > There are some rules : ceil of child <= ceil of parent, sum (child rates)
> > <= rate of parent ....  You don't have to follow this rules, but the
> > final shaping result can be strange.
> > See the faq page on www.docum.org.
>
> What would be nice is if you could document what happens when>
>      a) child ceil > parent ceil
Child ceil is used as maximum.

>      b) child rate > parent ceil
It depends on the child ceil.  Parent ceil is never used to limit the 
bandwidth.

>      c) child ceil > parent rate
>      d) child rate > parent rate
It's more complicated then this.  Other classes are also important.

> How does this influence the shaping results and the shaping of other
> classes? I've actually asked a similar question before: If you have
>
>            1:1
>            / \
>          /     \
>        1:2     1:3
>        /|\       \------
>      /	|  \       \     \
>    1:4 1:5 1:6     1:7   1:8
>
> if 1:7 and 1:8 respects the rate/ceil of 1:3 and 1:3 respects the rate/ceil
> of 1:1, but 1:4 does not respect the rate/ceil of 1:2 and 1:2 respects the
> rate/ceil of 1:1, does the shaping of 1:3 work as normal and only those
> classes under 1:2 are adversely affected or not? from your previous answer,
> it seems that the classes under 1:3 would not be affected, but I would love
> to know why. what happens with 1:4 requests some bandwidth which 1:2 does
> not have...
It's easier if you add some numbers of ceil/rate to understand the question.

I'm going to create an extra page on www.docum.org with your questions and my 
answer to explain how rate and ceil of classes and parent classes are used.  
Ok?

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Abraham van der Merwe]

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Hi Stef!

> > How does this influence the shaping results and the shaping of other
> > classes? I've actually asked a similar question before: If you have
> >
> >            1:1
> >            / \
> >          /     \
> >        1:2     1:3
> >        /|\       \------
> >      /	|  \       \     \
> >    1:4 1:5 1:6     1:7   1:8
> >
> > if 1:7 and 1:8 respects the rate/ceil of 1:3 and 1:3 respects the rate/ceil
> > of 1:1, but 1:4 does not respect the rate/ceil of 1:2 and 1:2 respects the
> > rate/ceil of 1:1, does the shaping of 1:3 work as normal and only those
> > classes under 1:2 are adversely affected or not? from your previous answer,
> > it seems that the classes under 1:3 would not be affected, but I would love
> > to know why. what happens with 1:4 requests some bandwidth which 1:2 does
> > not have...
> It's easier if you add some numbers of ceil/rate to understand the question.
> 
> I'm going to create an extra page on www.docum.org with your questions and my 
> answer to explain how rate and ceil of classes and parent classes are used.  
> Ok?

That would be great, thanks

-- 

Regards
 Abraham

If you didn't have most of your friends, you wouldn't have most of
your problems.

___________________________________________________
 Abraham vd Merwe [ZR1BBQ] - Frogfoot Networks
 P.O. Box 3472, Matieland, Stellenbosch, 7602
 Cell: +27 82 565 4451 Http: http://www.frogfoot.net/
 Email: abz@frogfoot.net


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Re: [LARTC] HTB and theory

[Stef Coene]

On Tuesday 10 December 2002 14:28, Abraham van der Merwe wrote:
> Hi Stef!
>
> > > How does this influence the shaping results and the shaping of other
> > > classes? I've actually asked a similar question before: If you have
> > >
> > >            1:1
> > >            / \
> > >          /     \
> > >        1:2     1:3
> > >        /|\       \------
> > >      /	|  \       \     \
> > >    1:4 1:5 1:6     1:7   1:8
> > >
> > > if 1:7 and 1:8 respects the rate/ceil of 1:3 and 1:3 respects the
> > > rate/ceil of 1:1, but 1:4 does not respect the rate/ceil of 1:2 and 1:2
> > > respects the rate/ceil of 1:1, does the shaping of 1:3 work as normal
> > > and only those classes under 1:2 are adversely affected or not? from
> > > your previous answer, it seems that the classes under 1:3 would not be
> > > affected, but I would love to know why. what happens with 1:4 requests
> > > some bandwidth which 1:2 does not have...
> >
> > It's easier if you add some numbers of ceil/rate to understand the
> > question.
> >
> > I'm going to create an extra page on www.docum.org with your questions
> > and my answer to explain how rate and ceil of classes and parent classes
> > are used. Ok?
>
> That would be great, thanks
I wrote some more information about ceil and rate.  You can find it on the faq 
page on www.docum.org under "Basic rules for traffic shaping with HTB".  If 
you have more questions, let me know and I will try to answer them.
Remember, htb will work if you don't follow this rule.  But it will be less 
obviuos to figure out how the bandwidth will be distributed.

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Abraham van der Merwe]

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Hi Stef!

> > > > How does this influence the shaping results and the shaping of other
> > > > classes? I've actually asked a similar question before: If you have
> > > >
> > > >            1:1
> > > >            / \
> > > >          /     \
> > > >        1:2     1:3
> > > >        /|\       \------
> > > >      /	|  \       \     \
> > > >    1:4 1:5 1:6     1:7   1:8
> > > >
> > > > if 1:7 and 1:8 respects the rate/ceil of 1:3 and 1:3 respects the
> > > > rate/ceil of 1:1, but 1:4 does not respect the rate/ceil of 1:2 and 1:2
> > > > respects the rate/ceil of 1:1, does the shaping of 1:3 work as normal
> > > > and only those classes under 1:2 are adversely affected or not? from
> > > > your previous answer, it seems that the classes under 1:3 would not be
> > > > affected, but I would love to know why. what happens with 1:4 requests
> > > > some bandwidth which 1:2 does not have...
> > >
> > > It's easier if you add some numbers of ceil/rate to understand the
> > > question.
> > >
> > > I'm going to create an extra page on www.docum.org with your questions
> > > and my answer to explain how rate and ceil of classes and parent classes
> > > are used. Ok?
> >
> > That would be great, thanks
> I wrote some more information about ceil and rate.  You can find it on the faq 
> page on www.docum.org under "Basic rules for traffic shaping with HTB".  If 
> you have more questions, let me know and I will try to answer them.
> Remember, htb will work if you don't follow this rule.  But it will be less 
> obviuos to figure out how the bandwidth will be distributed.

I think your explanation of "rate of class" in your FAQ is wrong. it
caught me as well, but from devik's faq page
(http://luxik.cdi.cz/~devik/qos/htb/htbfaq.htm):

------------< snip <------< snip <------< snip <------------
What if sum of child rates is greater than parent rate ?

Then interesting things can happen. Total rate delivered by children can be
higher that parent's rate (thus its rate is not respected). However when sum
of actual child rates are under parent's rate then borrowing will occur like
in regular case.

------------< snip <------< snip <------< snip <------------

Thus, if sum (rate of childs) > parent rate, then the parent rate is _not
respected_.

-- 

Regards
 Abraham

An American's a person who isn't afraid to criticize the president but is
always polite to traffic cops.

___________________________________________________
 Abraham vd Merwe [ZR1BBQ] - Frogfoot Networks
 P.O. Box 3472, Matieland, Stellenbosch, 7602
 Cell: +27 82 565 4451 Http: http://www.frogfoot.net/
 Email: abz@frogfoot.net


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Re: [LARTC] HTB and theory

[Stef Coene]

On Thursday 12 December 2002 09:36, Abraham van der Merwe wrote:
> Hi Stef!
> I think your explanation of "rate of class" in your FAQ is wrong. it
> caught me as well, but from devik's faq page
> (http://luxik.cdi.cz/~devik/qos/htb/htbfaq.htm):
>
> ------------< snip <------< snip <------< snip <------------
> What if sum of child rates is greater than parent rate ?
>
> Then interesting things can happen. Total rate delivered by children can be
> higher that parent's rate (thus its rate is not respected). However when
> sum of actual child rates are under parent's rate then borrowing will occur
> like in regular case.
>
> ------------< snip <------< snip <------< snip <------------
>
> Thus, if sum (rate of childs) > parent rate, then the parent rate is _not
> respected_.
:)
Devik is right, I'm wrong.  Do you know why I was convinced that my rule was 
OK?  Because I always followed my own rules :)

I did some small tests :


             ceil rate
1            200  200
 \- 10       200  100
     \- 100  200  100
     \- 101  200  100
 \- 20       200  100

Traffic in 100, 101 and 20 : each gets 67 (33%)
        Parent rate (10) is not respected otherwise 10 should share 50% with 
20.
Traffic in 100 and 20 : each gets 100 (50%)

If you respect "sum (rate of childs) = parent rate" it works like expected :

             ceil rate
1            200  200
 \- 10       200  100
     \- 100  200  50
     \- 101  200  50
 \- 20       200  100

Traffic in 100, 101 and 20 : 20 gets 100 (50%), 101 50 (25%) and 101 50 (25%).
Traffic in 100 and 20 : each gets 100 (50%)


Conclusion : if you want to know how traffic will be shaped, you have to 
follow some basic rules.
I will update docum.org tonight.

Stef

-- 

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

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Re: [LARTC] HTB and theory

[Abraham van der Merwe]

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Hi Stef!

> I did some small tests :

[snip]

> Conclusion : if you want to know how traffic will be shaped, you have to 
> follow some basic rules.
> I will update docum.org tonight.

You're right. I did some tests this weekend as well and realised that you
have to stick with the basics. The problem was that it was not so clear to
me how HTB behaves when the child's rates/ceil exceed the parent's.

Some other questions I'd like to ask you while I'm at it:

1) if you have:

                   1:1
                  /   \
                /       \
              1:2       1:3
              / \       / \
             /   \     /   \
           1:4   1:5 1:6   1:7

If

1:2 = prio 1
1:3 = prio 2

1:4 = prio 10
1:5 = prio 11

1:6 = prio 5
1:7 = prio 6

Is 1:4, 1:5 evaluated first or 1:6, 1:7? Iow, does HTB start at the root
node, prioritize its children and, subprioritize their children, etc. or
is only the leaf nodes' priorities important (i.e. 1:6, 1:7, 1:4, 1:5)

2) if a class is evaluated and there is some bandwidth available to borrow,
is the first non-congested child given all bandwidth that is available and
then the next is given the rest and so on or is each child given a quantum
of bandwidth, then if there is some bandwidth left, a second round and so on?

-- 

Regards
 Abraham

History repeats itself.  That's one thing wrong with history.

___________________________________________________
 Abraham vd Merwe [ZR1BBQ] - Frogfoot Networks
 P.O. Box 3472, Matieland, Stellenbosch, 7602
 Cell: +27 82 565 4451 Http: http://www.frogfoot.net/
 Email: abz@frogfoot.net


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Re: [LARTC] HTB and theory

[Stef Coene]

On Thursday 12 December 2002 12:19, Abraham van der Merwe wrote:
> Hi Stef!
>
> > I did some small tests :
>
> [snip]
>
> > Conclusion : if you want to know how traffic will be shaped, you have to
> > follow some basic rules.
> > I will update docum.org tonight.
>
> You're right. I did some tests this weekend as well and realised that you
> have to stick with the basics. The problem was that it was not so clear to
> me how HTB behaves when the child's rates/ceil exceed the parent's.
>
> Some other questions I'd like to ask you while I'm at it:
>
> 1) if you have:
>
>                    1:1
>                   /   \
>                 /       \
>               1:2       1:3
>               / \       / \
>              /   \     /   \
>            1:4   1:5 1:6   1:7
>
> If
>
> 1:2 = prio 1
> 1:3 = prio 2
>
> 1:4 = prio 10
> 1:5 = prio 11
>
> 1:6 = prio 5
> 1:7 = prio 6
>
> Is 1:4, 1:5 evaluated first or 1:6, 1:7? Iow, does HTB start at the root
> node, prioritize its children and, subprioritize their children, etc. or
> is only the leaf nodes' priorities important (i.e. 1:6, 1:7, 1:4, 1:5)
I don't know.  But I think only the leaf nodes are important.  I have some 
work to do tonight, but I hope to test it this evening.

> 2) if a class is evaluated and there is some bandwidth available to borrow,
> is the first non-congested child given all bandwidth that is available and
> then the next is given the rest and so on or is each child given a quantum
> of bandwidth, then if there is some bandwidth left, a second round and so
> on?
If each class received his rate and the parent has some bandwidth left, the 
bandwidth is distributed in a round robin so each class can send quantum 
bytes.

Stef

-- 

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

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