Packets processed by a SAP or subscriber egress child policer can have their forwarding class and profile state remapped to a different forwarding class and profile state after exiting the policer. Remapping is achieved by using a post-policer mapping policy containing mapping statements that determine the remapping of packets based on their forwarding class and profile state.
The post-policer mapping policy is configured as follows:
configure
qos
post-policer-mapping <mapping-policy-name> [create]
description <description-string>
fc <fc-name> profile <profile> [create]
maps-to fc <fc-name> profile <profile>
where:
<mapping-policy-name> is the name of mapping policy, up to 32 characters.
<description> is the description text string.
<fc-name> can be af, be, ef, h1, h2, l1, l2, or nc.
<profile> can be in, out, exceed, or inplus.
Up to 32 mapping statements are supported within a policy, covering the maximum combinations of eight forwarding classes and four profile states. A maximum of seven post-policer mapping policies can be configured per system.
After being configured, the post-policer mapping policy must be applied within a SAP egress QoS policy with, at most, one mapping policy per SAP egress QoS policy:
configure
qos
sap-egress <policy-id> [create]
post-policer-mapping <mapping-policy-name>
Packets entering a child policer are assigned a forwarding class and profile state. The configuration of the policer can change the profile state of the exiting packet, but not the forwarding class. If a post-policer mapping policy is applied within the SAP egress QoS policy, a packet exiting the policer with a specific forwarding class and profile state can be remapped to a different forwarding class and profile state. For example, consider the following post-policer mapping policy:
configure
qos
post-policer-mapping ppm1 create
fc ef profile exceed create
maps-to fc be profile out
exit
exit
Packets exiting an egress child policer with forwarding class ‟ef” and profile state ‟exceed” have their forwarding class remapped to ‟be” and their profile state to ‟out”.
The mapping applies to all policers within the SAP egress QoS policy, including regular child policers and policers configured in an IP/IPv6 criterion action statement, except for dynamic policers. The remapping does not affect the policer statistics or the parent policer processing (root arbiter) as it occurs after each of these.
The new forwarding class is used to select the egress queue on which the post-policer traffic is placed. The new profile is used to determine the congestion control handling in that queue and its pool, specifically the drop tail or slope that is applied.
Egress packet remarking is based on the marking configured for the forwarding class and profile of the traffic after being policed but before it is remapped.
This remapping is supported on platforms using FP3- and higher-based hardware, with the exception of the 7750 SR-a4/a8, which does not support egress policers.
Remapping a subset of packets from one forwarding class to another could result in out-of-order packets being received at the destination if there is congestion or different latency characteristics on the paths of the different forwarding classes.