Hello again Stefan,
>thank you for your time and help. You are right, i queued all
>traffic excect traffic from 192.168.0.101 to class 1:30 but with no
>special threatment for specific packages.
But, the important factor here is that your OpenWrt device is
managing the shaping and scheduling. That goes for both default
traffic and your VoIP traffic.
>So because i limited the link throughput, the upstream device was
>able to better deal with the packages it has to process and that
>improved the upload/download throughput.
Correct. But, more importantly the packets are no longer piling up
in congestion on the modem. So, the modem can pass packets through
right away and be ready to deal with the next.
>It seems to be better in terms of performance to limit the link on
>my "site" and avoid congestion at the upstream device.
Absolutely.
>Even though both devices have a queue i still do not see, why it's
>better to not let the modem do the "job".
The modem software/hardware was created to queue packets a certain
way and you didn't like how it did the job.
Without knowing your specific modem (it is unimportant, anyway), I
will assert that the problem with your modem is the problem that has
been described by Jim Gettys as 'buffer bloat' [0].
The gear and provider configurations that lead to 'buffer bloat'
result in two problems:
* deep queues trade throughput for latency (leading you to want to
prioritize your VoIP in the first place)
* deep queues cause strange and unpleasant interactions with
packet drops [which packet drops, in turn, cause unpredictable
throughput numbers]
You like better how your OpenWrt box is handling the queueing,
because it is making better tradeoffs between throughput and latency
(and packet dropping during saturation situations). All of this
results in a better experience for your users.
Since you added the HTB qdisc, you have taught your OpenWrt device
to "slow down" its dequeue rate so that the packet congestion occurs
on the OpenWrt device, not on the modem.
In short, you have just implemented the bottleneck rule [0]. Your
box has become the bottleneck (which is a good thing)!
Best regards,
-Martin
[0] https://gettys.wordpress.com/
http://www.bufferbloat.net/
[0] http://tldp.org/HOWTO/Traffic-Control-HOWTO/rules.html
--
Martin A. Brown
http://linux-ip.net/
--
To unsubscribe from this list: send the line "unsubscribe lartc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
