Re: [LARTC] CBQ and WRR

["Christian Worm Mortensen" <worm@dkik.dk>]

Hi,

> > Yes, but in the howto also a qdisc named WRR is mentioned.
> 
> What HOWTO?

This thread is on two mailing lists. One of the lists is for the howto located on http://ds9a.nl/2.4Routing/. This howto mentions the WRR qdisc (see http://wipl-wrr.dkik.dk/wrr/) which is a qdisc that is _not_ included in the standard kernel and has nothing to do with CBQ.

> WRR works well when you apriori know the packet/cell sizes (eg in ATM).
> If you cant do this, then WRR is unfair once you start having a lot of
> flows going or you mistweak your weights etc. DRR fixes this.

Hmm... Maybe you talk about how WRR/DRR is implemented in CBQ? A pure WRR scheduler works perfect no matter what size the packets have. If, of course, the scheduler takes packet sizes into account. What exactly is the problem with a WRR scheduler? 

Another thing: Unless you have a need to give special traffic very low delay I don't see any reason why you would want to use CBQ instead of pure WRR? I.e.: If you use CBQ with all prio parameters set to the same, why not use pure WRR instead?

> Why dont you read the classical paper at:
> http://www.acm.org/sigcomm/sigcomm95/papers/shreedhar.html

What I really need is a paper describing CBQ in Linux - the original article desribing CBQ is very generel. And when I experimented with CBQ the last time I did not see the behaviour I would exepect from the article assuming that the generel scehudler was a WRR scheduler.


Christian


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