[c-nsp] QoS on a 6509/720

[John Kristoff]

On Thu, 22 Sep 2005 16:32:31 +0200
<lists at hojmark.org> wrote:

> The best paper by far that I've seen is the QoS SRND available
> at www.cisco.com/go/srnd. I really think you should read that,
> as it has all the different terminology and technology actually
> put to use in a real world scenario.

Thanks, 280+ pages even.  I really needed more to read.  :-)  Looks
like a lot of it is stuff I've seen before, but certainly a good
reference I've missed.

> > [...] if 'mls qos' is applied globally and a port's QoS state
> > is untrusted, packets entering that port will have their ToS
> > (DiffServ codepoint) rewritten to the port's default (which
> > should typically be CS0 - best effort).  Is that still the case
> > with the box I'm running?
> 
> Yes, that is the case with any Catalyst.

Hmm... guess this might be an issue I'll have to take up with the TAC
then.

> No, that'll only work for edge ports with trust. Otherwise,
> the dscp will be 0, and the traffic will not be policed. You
> have to classify using some other characteristic of the traffic
> than dscp, typically port numbers and/or IP addresses.

Right thanks, I'll also intend to to set the edge ports to trust,
something I missed.  The one thing I've thought about, but I'm
not sure it's worth a lot of time worrying about now is whether
I should trust other codepoints besides best effort and scavenger.
While it may be unlikely, I wouldn't want an host to have the
capability to get their packets in a higher weighted queue or
applied to a less aggressive WRED drop policy (presuming I stick
with the default queue and drop settings).

John