RE: Q. Terribly confused about interface bandwidth used for QoS

From: Victor Cappuccio (cvictor@protokolgroup.com)
Date: Sat Sep 09 2006 - 20:28:07 ART

Then you in your case should set the bandwidth; since 154kbps (solution 2)
is more than 64Kbps (solution 1)

unless there was a specific reason to do so though"

Victor.-

  _____

De: sabrina pittarel [mailto:sabri_esame@yahoo.com]
Enviado el: Sabado, 09 de Septiembre de 2006 07:17 p.m.
Para: Victor Cappuccio; Brian McGahan; ccielab@groupstudy.com
Asunto: Re: Q. Terribly confused about interface bandwidth used for QoS
calculations - please help

I read, I read...
But he also said:
"In the lab exam I wouldn't worry about setting
bandwidth values unless there was a specific reason to do so though"

I'm trying to see if my example below *is* a specific reason :-)

Sabrina

----- Original Message ----
From: Victor Cappuccio <cvictor@protokolgroup.com>
To: sabrina pittarel <sabri_esame@yahoo.com>; Brian McGahan
<bmcgahan@internetworkexpert.com>; ccielab@groupstudy.com
Sent: Saturday, September 9, 2006 4:10:38 PM
Subject: RE: Q. Terribly confused about interface bandwidth used for QoS
calculations - please help

Sabrina, sorry to pzt my nose here
But read what brian said " In a practical application any time that the
link speed does not match the maximum transmission speed you should set
bandwidth value accordingly."

That for me means in your case that you need to set the BW command under the
Interface

Please again excuse me to jump at this thread

Victor.-

-----Mensaje original-----
De: nobody@groupstudy.com [mailto:nobody@groupstudy.com] En nombre de
sabrina pittarel
Enviado el: Sabado, 09 de Septiembre de 2006 06:57 p.m.
Para: Brian McGahan; ccielab@groupstudy.com
Asunto: Re: Q. Terribly confused about interface bandwidth used for QoS
calculations - please help

Thank you Brian,
I understand now, but let me take an example of a possible lab scenario

Assuming I have a P2P link with the DCE side clocked at 64000 and I'm asked
do guarantee 10% of the bandwitdh on both sides to a given flow X and *not*
to use the percentage keyword What would be the configuration of R1 and R2?

    1/1 1/1
  R1 -------------------------- R2
                           clockrate 64000

Solution1)
R1 

---
interface s1/1
   bandwith 64
   service-policy output s1/1-pm-out

policy-map s1/1-pm-out
   class X
     bandwith  6

R2
  ---
  interface s1/1
   clockrate 64000
    bandwith 64
    service-policy output s1/1-pm-out

  policy-map s1/1-pm-out
    class X
      bandwith  6

Solution2)
R1
  ---
  interface s1/1
    service-policy output s1/1-pm-out

  policy-map s1/1-pm-out
    class X
      bandwith 154    <<<<< 10% of 1544

  R2
   ---
   interface s1/1
    clockrate 64000
     service-policy output s1/1-pm-out

   policy-map s1/1-pm-out
     class X
       bandwith 154

Sabrina

----- Original Message ----
From: Brian McGahan <bmcgahan@internetworkexpert.com>
To: sabrina pittarel <sabri_esame@yahoo.com>; ccielab@groupstudy.com
Sent: Saturday, September 9, 2006 3:15:00 PM
Subject: RE: Q. Terribly confused about interface bandwidth used for QoS
calculations - please help

    In a practical application any time that the link speed does not
match the maximum transmission speed you should set bandwidth value
accordingly.  For example suppose you have a FastEthernet interface
connected to your service provider but they are policing your traffic to
5Mbps.  If you issue the "bandwidth percent 75" command under the MQC
you would be configuring a bandwidth guarantee beyond your reservable
capacity.  The same case would hold true for serial interface, atm
interfaces, etc.  In the lab exam I wouldn't worry about setting
bandwidth values unless there was a specific reason to do so though.

HTH,

Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com

Internetwork Expert, Inc.
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> sabrina pittarel
> Sent: Saturday, September 09, 2006 4:06 PM
> To: ccielab@groupstudy.com
> Subject: Q. Terribly confused about interface bandwidth used for QoS
> calculations - please help
>
> Hi all,
>  can somebody help me clarify what is the interface bandwith used for
QoS
> calculations in various interface types?
>  * Ethernet interface:
>
>  R1 ------------- R2
>     fe          e
>
>  R1 will auto negotiate a 10M speed with R2.
>  10Mbps will be used on R1 and R2 for QoS calculations. No need for
> explicit interface configuration.
>
>  * Serial P2P interface Clocked at 64000
>
>  R1 ------------- R2
>               clockrate 64000
>
>  How the configured clockrate will affect reference bandwidth for QoS
> calculation?
>
>  Should we configure "bandwidth 64" on R1 and R2 serial interfaces?
>  In my understanding the clockrate value determines how fast we can
really
> transmit on the media, but I don't see QoS calculations use that value
as
> reference number. Should we then configure the bandwidth command?
>  Similar question for routing protocols.
>  Should we alter default interface OSPF cost/eigrp interface bandwitdh
in
> respect to the media clocking?
>
>  Sabrina
>
>

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