RE: [LARTC] Question on prio qdisc

[Leonardo Balliache <leoball@opalsoft.net>]

Hi, Lars:

At 10:10 a.m. 08/07/03 +0200, you wrote:

> >
> > each queue is an independent queue. Then if high priority packets are
> > dropped is because the high priority queue has overflow, not because some
> > (unique?) queue is full from low priority packets.
>
>I am little confused.  If typed ifconfig, we can see "txqueuelen:100".
>Will this imply that all three bands hold by prio are sharing this 100
>packages capacity, or can each of these three bands each occupy 100
>packages in its buffer.  In the latter, this means prio can maximum occupy
>300 packages...
>
>This problem will also imply HTB and other schedulers..
>
>
>Regards
>
>Lars Landmark

I'm not very sure if the total queue length is 100 or 300 because I was
searching the code and I can't find any information that tell me what the
real length is.

Because "ip link" shows me that qlen is 100, I have to suppose that total
length is 100.

But anyway, PRIO queing discipline principle calls that each priority queue
is independent, then we can't have the prio 0 queue full of prio 1 or 2
packets (being the filters working well). It goes against the PRIO queuing
discipline principle.

In "Differentiated Service on Linux HOWTO" (work in progress) I present
a PRIO queuing discipline explanation using some documentation taken
from Juniper Networks. Have a look at http://opalsoft.net/qos.

Also if you read about Cisco PQ the principle is identical. If we don't
respect the principle, then the queue can be any sort of queue, but
certainly, not a PRIO queue. Then it´s not posible to ask on PRIO for something
that drops an already enqueue packet to make run for a new arriving one.

I suggest that configurations and tests made to reach that conclusions were 
revised.

Best regards,

Leonardo Balliache





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