RE: QOS Conundrum - bandwidth, shape average or shape peak?

From: Wollmann, Bruno RQHR (Bruno.Wollmann@rqhealth.ca)
Date: Mon Jan 07 2008 - 01:10:11 ARST


You want to use SHAPE AVERAGE for the PREC2 traffic. SHAPE PEAK will
allow more than 128K if it's available (how much more I don't know).
Using BANDWIDTH 128 for PREC2 will guarantee 128K of bandwidth and allow
more (upto the interface bandwidth) if there is no congestion, it will
not limit it to 128K. You definitely don't want to use BANDWIDTH.

HTH
Bruno

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Mark Turner
Sent: January 6, 2008 5:07 PM
To: ccielab@groupstudy.com
Subject: QOS Conundrum - bandwidth, shape average or shape peak?

Hello,

I am trying to solve the below question. I have included the
configuration that I believe will work. I am just unclear as to the best
method to rate limit to a specific value if rate limiting and policing
are specifically forbidden. I have narrowed it down to the shape
average, shape peak or bandwidth statement but cant decide which to use.

"Configure R2 so that traffic marked with the precedence value 3 AND/OR
traffic from VLAN_C (1.1.1.1) to VLAN_BB2 (2.2.2.2) is guaranteed
minimum of 128K of bandwidth when sent out of interface fast 0/0. If
congestion occurs assure this traffic is randomly dropped. Also make
sure that traffic marked with prec value 2 is rate limited to 128K. Do
not use rate-limiting or policing."

Access-list 100 permit ip 1.1.1.0 0.0.0.255 2.2.2.0 0.0.0.255

class-map match-any prec3
  match ip precedence 3
  match access-group name prec3
!
class-map match-any PREC2
  match ip precedence 2
!
policy-map cisco
  class VLANC-TO-VLAN_BB2
   bandwidth 128
   random-detect
  class PREC2
  shape average 128000 -> my best guess

OR
 class PREC2
  shape peak 128000

OR
 class PREC2
  bandwidth 128



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