[c-nsp] [Fwd: Re: QoS possible on the 7600 Sup720-3bxl?]

Tue May 23 06:48:14 EDT 2006

Jose,

With PFC QoS you cannot schedule priority percentages (or percentages in
general).

Depending on what you want:
 - If you want to limit bandwidth, use (flow or microflow) policers.
 - If you don't want to limit bandwidth, then traffic will be forwarded
on a best-effort basis based on  COS (which is derived from DSCP/IP PRI
etc).

use 'show queueing interface xxx/x' to see how your queues are set and
how many drops you have. This will enable you to make an informed
decision.

Remember that the aim of PFC QoS is to enable line-speed forwarding at
interface level, so you cannot do much at that point. If you want to do
any decent QoS processing, this needs to be done on the PFC.

Chris.

-----Original Message-----
From: The Father [mailto:the_father at allstream.net] 
Sent: 23 May 2006 11:09
To: cisco-nsp at puck.nether.net; Bisazza, Chris
Subject: [Fwd: Re: [c-nsp] QoS possible on the 7600 Sup720-3bxl?]

Chris,

Here's the text from a previous response I sent which has my configs.
Hope you can figure something out from them:

Thanks for the suggestion.  I did something similar to what you wrote
below and here's my config and subsequent error messages:

access-list 76 permit any
access-list 101 permit ip any 192.168.41.0 0.0.0.255
!
class-map match-any all-traffic
description Match all traffic
match access-group 76
!
class-map match-any ACL101
description Match priority block
match access-group 101
!
policy-map test-voice-lan
class ACL101
  set mpls experimental imposition 5
   priority percent 33
class all-traffic
  set mpls experimental imposition 1
   bandwidth percent 66

Trying to apply the policy-map outbound resulted in this error:

7609-lab(config-if)#service-policy output test-voice-lan %Priority
command with parameter not supported on GE-WAN4/1. Please configure
police along with priority to limit the amount of traffic on priority
class 7609-lab(config-if)#

I tried making the config changes as suggested in the error message and
then I got this:

7609-lab(config)#int ge-4/1 7609-lab-hcap(config-if)#service-policy
output test-voice-lan %PRIORITY command with "match access-group" class
not supported on GE-WAN4/1 7609-lab(config-if)#

So I decided to change both queues to CBWFQ and this is what I got:

7609-lab(config)#int ge-4/1
7609-lab(config-if)#service-policy output test-voice-lan %Weighted Fair
Queuing with "match access-group" class not supported on GE-WAN4/1
7609-lab(config-if)#

It looks like the router doesn't like matching on ACLs for this
particular setup.

Jose

Bisazza, Chris wrote:
> Note that the 7600 is different to standard routers where QoS is 
> concerned (it's PFC QoS).
>
> 1. You cannot schedule output based on MPLS e-tags, you can only use 
> the 'match mpls experimental' option to apply it to something else. 
> (COS comes to mind). Note that setting the priority of a packet will 
> (by
> default) re-write the DSCP values of your packet to match that value
> (unless you configure it otherwise). 
>
> Personally I think it's safer to match the packets you want to modify 
> using an ACL (or similar) and set the DSCP values for those packets.
>
>   
>
> 2.
>   
>> I've recently found out that the 7609 can only match on packet values
>> that exist before it enters the router.
>>     
>
> not 100% true. Traffic will generally only pass through the PFC once, 
> however, which means that you can only do one PFC operation. Setting 
> the MPLS e-tag is one such operation. QoS is also applied (separately)

> on output. The PFC operation is different to the queueing function.
>
> Note that the policy-maps (or samples of them) would be useful in 
> determining what you're trying to do.
>
> Chris.
>
>
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