[c-nsp] Cisco 6509-E QoS Policy Confusion

[Arie Vayner (avayner)]

Craig,

Basically you are making sure the customer is not abusing the different
classes.
For example any packet that goes beyond the policer in class
EF_QOS_PORTS would be remarked (this is the " exceed-action
policed-dscp-transmit violate-action policed-dscp-transmit" part) to a
lower value.

To see the value of the remark, you should use this command:
router#show mls qos maps policed-dscp
   Normal Burst Policed-dscp map:
(dscp= d1d2)
     d1 :  d2 0  1  2  3  4  5  6  7  8  9
     -------------------------------------
      0 :    00 01 02 03 04 05 06 07 08 09
      1 :    10 11 12 13 14 15 16 17 18 19
      2 :    20 21 22 23 24 25 26 27 28 29
      3 :    30 31 32 33 34 35 36 37 38 39
      4 :    40 41 42 43 44 45 46 47 48 49
      5 :    50 51 52 53 54 55 56 57 58 59
      6 :    60 61 62 63

   Maximum Burst Policed-dscp map:
(dscp= d1d2)
     d1 :  d2 0  1  2  3  4  5  6  7  8  9
     -------------------------------------
      0 :    00 01 02 03 04 05 06 07 08 09
      1 :    10 11 12 13 14 15 16 17 18 19
      2 :    20 21 22 23 24 25 26 27 28 29
      3 :    30 31 32 33 34 35 36 37 38 39
      4 :    40 41 42 43 44 45 46 47 48 49
      5 :    50 51 52 53 54 55 56 57 58 59
      6 :    60 61 62 63

For reference, search for "policed-dscp-transmit" on this page:
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/con
figuration/guide/qos.html


Usually this kind of policy is deployed on the ingress of the network
(where a customer is connected) and the remark makes sure that any
excess traffic from each class is marked down either to BE or a lower
class (depends on policy)


Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Craig Allen
Sent: Wednesday, March 04, 2009 14:26
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Cisco 6509-E QoS Policy Confusion

Hello,
 
I have recently taken over a network and have a question about a current
QoS policy and am trying to understand why it would have been configured
this way.
 
An excerpt of the questionable config is as follows:
 
policy-map apply_1000_qos_for_att_dscp_to_nextlevel
  class EF_QOS_PORTS
   police cir 4000000000 bc 3125000 be 31250000 conform-action
set-dscp-transmit ef exceed-action policed-dscp-transmit violate-action
policed-dscp-transmit
  class af31_QOS_PORTS
   police cir 4000000000 bc 31250000 be 31250000 conform-action
set-dscp-transmit af31 exceed-action policed-dscp-transmit
violate-action policed-dscp-transmit
  class af21_QOS_PORTS
   police cir 1000000000 bc 31250000 be 31250000 conform-action
set-dscp-transmit af21 exceed-action policed-dscp-transmit
violate-action policed-dscp-transmit
!
 
The above policy has been applied to all Gig interfaces on the 6509
blades.
 
What I'm trying to understand is the CIR / BC / BE settings and exactly
what they will achieve.
 
My first initial thought is that the CIR/BC/BE settings will achieve
nothing?
 
Thanks!
 
Craig
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