Let's look at 4 examples:
Marking based on Policing state
ASR9K supports setting a field based on the policer result. Consider the following policy-map,
Policy-map parent
Class class-default
Police rate 10 Mbps peak-rate 20 mbps
conform-action set dscp af12
conform-action set cos 2
exceed-action set dscp af13
exceed-action set cos 3
If the traffic rate is 0-10 Mbps the conform-action of setting dscp to af12 & cos 2 is executed. If the traffic rate is 10-20 Mbps, then the exceed-action of setting dscp to af13 and cos 3 is executed.
Marking and hierarchical policy-map
This section explains when using marking and policing based marking on a hierarchical policy-map what the expected behavior is. Note in ASR9K, in a 3 level explicit MQC policy hierarchy set/mark action is supported on only the bottom two levels in hierarchy. MQC describing ordering of feature-execution and indicates the following
- Set/Mark actions independent of policer would be executed first from TOP of the hierarchy to bottom.
- Set/Mark actions based on policer would be executed next from bottom of the hierarchy to the top.
Policy-map parent
Class class-default
Set cos 1
Set dscp AF11
Police rate 10 Mbps peak-rate 20 Mbps
conform-action set dscp af12
conform-action set cos 2
exceed-action set dscp af13
exceed-action set cos 3
violate-action drop
service-policy child
policy-map child
Class c1
Set cos 4
Set qos-group 1
Police rate 5 Mbps peak-rate 10 Mbps
conform-action set qos-group 2
conform-action set cos 5
exceed-action set qos-group 3
exceed-action set cos 6
violate-action drop
class class-default
!
For e.g. in the above policy-map hierarchy let’s consider the traffic is in conform state on both parent and child policer, then the order of execution is as follows
- set cos 1 (parent policy)
- set dscp AF11 (parent policy)
- set cos 4 (child policy – overrides step 1)
- set qos-group 1 (child policy)
- set qos-group 2 (child policy, policer conform state, overrides step 4)
- set cos 5 (child policy, policer conform state overrides step 3)
- set dscp af12 (parent policy, policer conform state, overrides step 2)
- set cos 2 (parent policy, policer conform state overrides step 6)
End result for such a flow is to set
- cos 2
- dscp af12
- qos-group 2
Similarly for other traffic effective mark actions can be derived as shown below.
|
Packet belonging to
|
Child policer state
|
Parent policer state
|
Marking actions performed
|
|
Child-C1
|
Conform
|
conform
|
Cos 2
Dscp af12
Qos-group 2
|
|
Child-C1
|
Conform
|
Exceed
|
Cos 3
Qos-group 2
Dscp af13
|
|
Child-C1
|
Conform
|
Violate
|
Drop
|
|
Child-class-default
|
X
|
Conform
|
Set cos 2
Set dscp AF12
|
|
Child-class-default
|
X
|
exceed
|
Set cos 3
Set dscp AF13
|
|
Child-class-default
|
X
|
violate
|
Drop
|
|
Child-c1
|
Exceed
|
Conform
|
Set cos 2
Set dscp AF12 Set qos-group 3
|
|
Child-c1
|
Exceed
|
Exceed
|
Set cos 3 Set dscp AF13
Set qos-group 3
|
|
Child-c1
|
Exceed
|
violate
|
Drop
|
|
Child-c1
|
Violate
|
Don’t Care
|
Drop
|
Single Rate policer (1R2C)
ASR9K would instantiate a single Rate 2 color policer when user configures just one rate associated to a policer in the policy-map. For e.g.
Policy-map policer
Class class-default
Police rate 10 Mbps
Conform-action transmit
Exceed-action drop
For the above policy-map if the traffic is <=10 Mbps, the policer would take any action configured under “conform-action” sub-mode. In this case if traffic is <=10, it would be transmitted, if > 10 Mbps it would be dropped.
Note an optional burst size can be configured for the rate, to limit the length of burst in addition to the rate. If this optional burst size is not specified, then a 100ms burst size of the rate specified is used internally.
Policy-map policer
Class class-default
Police rate 10 Mbps burst 100 kbytes
Conform-action transmit
Exceed-action drop
Dual Rate policer (2R3C)
When a peak-rate needs to be enforced separately from a committed rate, a 2R3C policer can be utilized. In ASR9K when user specifies two rates (rate & peak-rate) a 2R3C policer would be instantiated. For e.g.
Policy-map policer
Class class-default
Police rate 10 Mbps peak-rate 20 Mbps
Conform-action transmit
Exceed-action set cos 0
Violate-action drop
In the above policy-map, if traffic is <=10 Mbps it is transmitted. If 10Mbps< traffic <= 20 Mbps then the cos is remarked as 0 and packets are transmitted. If the traffic is > peak-rate then it is dropped.
Note once again optional burst size can be configured for the rate as well as peak-rate, to limit the length of burst in addition to the rate. If this optional burst size is not specified, then a 200ms burst size of the rate specified is used internally.
Policy-map 2R3C_policer
Class class-default
Police rate 10 Mbps burst 10 kbytes peak-rate 20 Mbps peak-burst 20 Kbytes
Conform-action transmit
Exceed-action set cos 0
Violate-action drop
Let me know if you have any further questions.
Sam
