Re: [LARTC] Classes and qdiscs

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

On Thursday 13 March 2003 01:57, S Mohan wrote:
> I've been reading the posts on classless queuing and classes/qdisc
> combinations. Both Martin and Stef mentioned that one class can have
> more than one qdisc attached.
No.  One class can has 1 qdiac attached.  But there are qdiscs with multiple 
classes and you can add a qdisc to each of these classes.

> The way I had understood queue disciplines was as follows:
>
> 1. A class has a qdisc to regulate traffic under limit e.g htb/tbf....
Not really.  The qdisc is only responsible for sending the traffic that 
belongs to that class.

> 2. A tier in the hierarchy has a qdisc attached for sharing of spare
> bandwidth not utilized by one or more classes amongst the others in the
> same tier.
>
> Or would it be correct to say that each class has a qdisc that
> distributes its spare bandwidth to others in the same level in the
> hierarchy? Does it mean that if I have SFQ for one class and have not
> attached SFQ to the other two classes at the same level, the other two
> classes would get even distribution of bandwidth not utilized by the
> first class?
Classes are responsible for managing the traffic.  Each class sholds a part of 
the total traffic.  Unused bandwidth can be shared amongs the differenc 
classes.
If you want to understand how traffic is managed between classes, forget about 
the qdiscs.  Just think about the classes.  The qdiscs are only responsible 
for sending the traffic.  The amount of traffic is regulated by the 
configuration of the classes.

Stef


-- 

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

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