freebsd stable - Oct 2006 - altq on tun0: queueing works, prioritization not?

Hello all,

I tried to set up TCP ACK prioritization with pf/altq as has been
described on various places of the internet.

It doesn't work as expected. I have a 16Mb/1Mb DSL link, the modem is
connected to a dc(4) device, I'm working with the tun0 device for my
firewall rules. Here they are:

ext_if="tun0"
scrub in all
altq on tun0 priq bandwidth 400Kb queue { std, http, ssh, dns, tcp_ack }

queue std     priority 1 priq(default)
queue tcp_ack priority 6

pass out on $ext_if proto tcp from any to any queue(std, tcp_ack)


Please note that I tried various bandwidth settings, for testing
purposes I set it to a very very low 400kb.

When downloading from ftp.de.freebsd.org, I'm able to achieve roughly
950kB/s. If I then start an FTP upload (which will reach some 42kB/s, so
the 400kb bandwidth is in effect), the interface throughput drops down
to a mere 120kB/s.

The 400kb limit should also be low enough, as I'm able to upload to that
same ftp with up to 100kB/s if I turn off queueing.

This is definitely not what I would expect. Where is my error?

Ulrich Spoerlein
-- 
A: Yes.
>Q: Are you sure?
> >A: Because it reverses the logical flow of conversation.
> >>Q: Why is top posting frowned upon?

Ulrich Spoerlein wrote:
> This is definitely not what I would expect. Where is my error?
Oh well, I should have tried 'cbq' earlier. With the following settings
(renamed the queues)

altq on $ext_if cbq bandwidth 800Kb queue { q_pri, q_std }
queue q_pri priority 6 cbq(borrow)
queue q_std priority 1 cbq(default borrow)

I'm actually able to achieve some effect. The upload is capped at
70-80kB/s and the download will fluctuate between 580 and 750 kB/s.
Much better than the plain priority queuing.

As soon as I cut the upload, the download will jump back to
950-1000kB/s.

Is this discrepancy (pri vs. cbq) known?

Ulrich Spoerlein
-- 
A: Yes.
>Q: Are you sure?
> >A: Because it reverses the logical flow of conversation.
> >>Q: Why is top posting frowned upon?