[c-nsp] QoS on a 6509/720

[lists at hojmark.org]

> I have a mandate (so don't try to stop me :-) to implement QoS
> knobs on a network motivated by a VoIP deployment.  I've been 
> reading my fair share of Cisco doc, RFCs, research/workshop
> papers and others' implementation reports and now my brain is
> really starting to hurt.

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.

> [...] 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.

> I could do something like:
> 
>   mls qos
>   !
>   class-map match-all dscp-ef
>     match dscp ef
>   !
>   policy-map edge-ingress
>     class dscp-ef
>       police flow mask src-only 128000 4000 conform-action 
> transmit exceed-action drop

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.

-A