Re: Hierarchical QoS !

From: huan@huanlan.com
Date: Fri Jul 18 2008 - 08:42:44 ART

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Hmmm,

In your example, you use MAIN INTERFACE, and I think the two configurations do exactly the same.

The difference exist if you try to apply the config on a sub-interface. The second one can not be applied, because by default sub-interfaces do not support queues.

The first (hearachical) configuration creates queues by "shapping", and therefore you can apply bandwidth reservation in the child policy.

DOC CD has an example about this "work-arround". Do not remember the link though. I am sure, you would easily find it in QoS section.

--- On Fri, 7/18/08, Huan Pham <pnhuan@yahoo.com> wrote:
From: Huan Pham <pnhuan@yahoo.com>
Subject: Re: Hierarchical QoS !
To: "Cisco certification" <ccielab@groupstudy.com>, "Doan Dung Chi" <dungchid@gmail.com>
Date: Friday, July 18, 2008, 9:14 PM

Hi,

I do not see any difference. Maybe I am color blind :-)

Cheers,

--- On Fri, 7/18/08, Doan Dung Chi <dungchid@gmail.com> wrote:
From: Doan Dung Chi <dungchid@gmail.com>
Subject: Hierarchical QoS !
To: "Cisco certification" <ccielab@groupstudy.com>
Date: Friday, July 18, 2008, 8:19 PM

Hi GS !

Please explain what is the deference btw 2 ways of QoS Configuration :

Method 1:

class-map match-all PRE2
 match ip precedence 2
class-map match-all PRE3
 match ip precedence 3
!
policy-map PARENT
 class PRE2
 shape average 512000
 service-policy CHILD-PRE2
 class PRE3
  shape average 1024000
  service-policy CHILD-PRE3
!
policy-map CHILD-PRE2
 class class-default
  bandwidth 256
policy-map CHILD-PRE3
 class class-default
  bandwidth 512
!
interface serial 1/0
service-policy output PARENT

Method 2:

class-map match-all PRE2
 match ip precedence 2
class-map match-all PRE3
 match ip precedence 3
!
policy-map PARENT
 class PRE2
 shape average 512000
 bandwidth 256
 class PRE3
  shape average 1024000
  bandwidth 512
!

interface serial 1/0
service-policy output PARENT

In my understand, Interface will allocate bandwidth of 256kbps for Class PRE2
& 512kbpp for Class PRE3 when congestion occur in Method 1. However, In
Method
2, I don't understand how Interface process queue.
Correct me if I am wrong !

Thanks

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