[c-nsp] QOS - 6509 - Next Step?

[nealr]

  Paul,

     We're working on this now with some of the smaller switches. I just 
had to give an encapsulation of what I'd learned about the 3550 through 
3750 line and egress queueing. I think you'll find these principles 
apply to the 6500 but there are varying features based on line cards.

     IP precedence and DSCP are layer 3 markings for QoS. When the 
traffic is to egress a switch these pieces of information must first be 
mapped to one of eight CoS values, and then the CoS values themselves 
must be assigned to one of four (on 3550 - 3750) egress queues. Within 
the egress queues themselves there can be two different thresholds 
before discard begins which allows for some granuality within the queue. 
Congestion control may be tail drop or WRED. Some switches support the 
use of one of their four queues as a FIFO priority queue.

   Interesting stuff - I'm facing no fewer than three definite projects 
and two others that are very likely where diffserv domains on Catalyst 
3550, 3650, and 3750 play a role. I'm glad to see I'm not the only one 
wrestling with this stuff.


                                                                                            
Neal


Paul Stewart wrote:
> Hi there...
>
> I'm working on providing priority within our core of 6509's  and prefer to
> do marking via NBAR.  Is this a very bad idea in general?  We have NBAR
> support in all our routers pretty much throughout...
>
> This is not to address congestion as our core and distribution has no
> congestion (referring to maxxing out link speeds etc. specifically)...
>
> So I have started working with several VLAN interfaces on our 6509 (layer 3
> interfaces) and have DSCP=EF for SIP/MGCP/RTP traffic like this:
>
> class-map match-any QOS-VOIP
>   match protocol sip
>   match protocol rtp
>   match protocol mgcp
> !
> !
> policy-map QOS
>   class QOS-VOIP
>    set dscp ef
>   class class-default
>    set dscp default
>
> interface Vlan104
>  description xxxxxxxxxxxxxxxxxxx
>  bandwidth 100000
>  ip address xxx.xxx.xxx.105 255.255.255.248
>  ip nbar protocol-discovery
>  service-policy input QOS
>
> On VLAN interfaces I can only apply the service policy inbound - not
> outbound:
>
> dis1-rtr-mb(config-if)#service-policy output QOS
> MQC features are not supported in output direction for this interface
>
> I don't believe this is a problem because I understand that QOS is applied
> in one direction only - outbound, which on a VLAN layer3 interface would
> actually mean traffic *leaving* the interface is marked .. correct??
>
> So, I've been doing a lot of reading from "End-to-End QOS Network Design"
> which is a great book... I'm faced right now with too much information..;)
>
> Next step would be to assign queues on the actual interfaces?  Can I assign
> queues to vlan interfaces or only physical interfaces?  My problem is that
> the cards are 6148 and 6248 cards so limited queues.... as I understand it
> the 6248 is 1Q4T and the 6148 is 1P2Q2T?
>
> I hope someone can point me in the right direction for the "next step"...;)
>
> Thanks very much,
>
> Paul
>
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