QoS

Class Map

A class map is a set of rules to classify traffic.

Define Class Map

Class maps operate in two modes:

Match all modes. Requires all circumstances be fulfilled
Just matching a criterion is enough to classify the class as defined.
class-map match-all CNAME

Create a match all class map and enter in class map config mode

class-map match-any CNAME

Create a match any class map and enter in class map config mode

no class-map CNAM

Removes a class map

Example :
n1(config)# class-map match-all cmap1 n1(config-cmap)#

Define matching criteria

As said, a class map is a tool to classify traffic. so we need to define criteria.
The keyword match is used to define a rule for matching. A packet could be matched against its source, destination, etc.

match any

Every packet is accpeted.

no match any

Negate match any command and remove it from criteria

[no] match access-list ACL

Note

Only permit rules in ACL are considered.

[no] match source-address A.B.C.D/M

[no] match destination-address A.B.C.D/M

[no] match source-address X:X::X:X/M

[no] match destination-address X:X::X:X/M

[no] match dscp (0-63)

Match against packet DSCP value

[no] match protocol (0-63)

Match against packet protocol number

Example :
n1(config-cmap)# match destination-address 200.1.2.2
n1(config-cmap)# match access-list acl1

Policy Map

A policy map is a set of traffic policies attached to an interface.
Currently, the only policy available is traffic policing. Policy map uses class maps as a base and defines policies based on the class map.

Define Policy Map

policy-map NAME

Create a policy map

no policy-map NAME

Delete a policy map

Define a new policy

class CNAME

Enter class map policy config mode

police BPS [NORMALBURST [MAXBURST]] conform-action ACTION exceed-action ACTION [violate-action ACTION]

Define a police policy for entered class map. In the above command, BPS is the average bitrate of this traffic class.

NORMALBURST and MAXBURST are token buckets’ sizes.

ACTIONs are : transmit, drop and set-dscp-transmit. and the conditions are conform, exceed and violate ( which is optional).

transmit and drop actions, work as their names suggest. The set-dscp-transmit action allows the traffic to be passed. But the DSCP value of the packet is changed.

conform condition, is when data burst, is below the NORMALBURST rate. The exceed condition is when the data burst is between NORMALBURST and MAXBURST.

violate condition, is when data burst, is over MAXBURST rate. When a violate-action is not defined, the algorithm is just a single token bucket algorithm and only conform ( below NORMALBURST) and exceed ( over NORMALBURST) occurs.

no class CNAME

Remove all policies defined for a class map

no police

Remove police policy defined for a class map

Example :
n1(config)# policy-map pmap1
n1(config-pmap)# class cmap1
n1(config-pmap-c)# police 100K conform-action transmit exceed-action drop
n1(config-pmap)# class cmap2
n1(config-pmap-c)# police 10K conform-action transmit exceed-action set-dscp-transmit 24 violate-action drop

Apply to interface

Currently a policy map can be applied to just ingress traffic.

service-policy PMAP in

Example :
n1(config-if)# service-policy pmap1 in

Show commands

show policy-map [NAME]

Example :

n1(config)# do sh policy-map pmap1

Policy Map pmap1
   Class cmap
      Police CIR 102400 (bps) CB 25600 (byte) EB 35840 (byte)
      Conform Action : Transmit
      Exceed Action : Drop

Debugging logs can be set in case of need.

[no] debug qos event

log data plane installation processes and results