Re: [LARTC] HTB: quantum vs. burst

[Stef Coene <stef.coene@docum.org>]

On Thursday 16 January 2003 14:34, Pavel Mores wrote:
> Hello,
>
> a quick question: what exactly is the difference between quantum and
> burst in HTB?
>
> Original HTB documentation states the following with respect to
> quantums:
>
> "... when more classes want to borrow bandwidth they are each given some
> number of bytes before serving other competing class. This number is
> called quantum."
>
> Burst is defined like this:
>
> "The burst and cburst parameters control the amount of data that can be
> sent at the maximum (hardware) speed without trying to serve another
> class."
>
>
> From the quotes, the purpose of quantums and both burst parameters seem
> to be somewhat related, one might say overlapping.  Is it that quantums
> apply in different situations than bursts?  If so, when is each of
> quantum, burst and cburst applicable?
Quantum and bursts have nothing common.  Quantum is used to share remaining 
bandwidth between child classes.  So each class can send "quantum" bytes.  
Each class is controlled with 2 buckets, one for the rate, one for the ceil.  
These buckets have also a burst and this is burst for rate and cburst for 
ceil.

Very simplified situation as example : So even if you have a big quantum of 
let's say 60.000 bytes and you have a ceil of 6.000 bytes/s, you can only 
send 6.000 packets / second so it takes 10 seconds to send.  But if you have 
a burst of 30.000 byts/s and you have a very fast connection, you can send 
30.000 bytes very fast, but the remaining packets are send at ceil speed so 
6.000 bytes/s.  So it will take 5 seconds to send all the data.

Some more info abot quantum can be found on www.docum.org on the faq page.

Stef


-- 

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

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