[c-nsp] configure 876 with qos

[Adrian Chadd]

On Tue, Jul 17, 2007, Dennis Breithaupt wrote:

> What exactly does the "cbr"-adjustment do under the pvc? Does it have an real
> effect on data flow or is it just an administrative/management configuration?

Read up on the command; it influences the available bandwidth amount which
the QoS math uses to slice up intervals.

> We're having the problem, that we have a load auf 100% on our ADSL-lines on the
> upstream, because we're uploading massive background traffic. That leads to
> horrible high latency times. So we want to achieve, that we're only using i.e.
> 80% of the upload bandwidth.

Understandable.

> Sadly we can't use "bandwidth average" in the service policy, because the 836
> (in our case), but I think the 876, too, can't shape on ATM. (afaik)

Yes you can for upstream traffic. Shaping on upstream can also affect
downstream TCP traffic if you know what you're doing, but I'd then
suggest my "classify on ADSL RX, police/shape on ethernet TX" method for
those CPE devices.

> Is that the case? Our has cbr an effect on bandwidth limiting, too?
> 
> Can I also combine WRED with this adjustment? My tries with WRED were not
> successfull, because the OutQ was always "0".

Look at http://cisco.cluepon.net/index.php/Deployment_Applications/DSL_CPE_QoS ;
its an example which was put together to record a -working- CPE VoIP/ADSL
deploy. You can write different traffic class rules to classify your
upload traffic and give it lower priority - or force it to have a capped max -
and insert it into the ADSL TX policy.

(Caveat: this only handled QoS guarantees in the ADSL TX direction and
the ISP (as almost is always the case with DSL) didn't provide any QoS
in the ADSL RX direction; but the TX was what congested and caused
the perceived issues. It should be right for you.)

(I do this all the time on client 857's and 877's here; I even occasionally
do it on my Cisco 827 at home when "stuff" needs to be throttled.)




Adrian