To optimize both scale and performance, policy match-criteria entries configured by the operator are compressed by each FP4 line card before being installed in hardware.
This compression can result, in an unexpected scenario typically only achieved in a lab environment, in an overload condition where entries for a line card QoS policy on a line card FP are not programmed. This overload condition can occur when applying a QoS policy for the first time on a line card FP or when adding entries to a QoS policy.
A policy is installed for the first time on a line card FP if no router interface, service interface, SAP, spoke SDP, mesh SDP or ESM subscriber host was using the policy on this FP.
A policy installed for the first time on a line card FP can lead to a compression failure resulting in an overload condition for this policy on this FP. In this case, none of the entries for the affected QoS match-criteria policy are programmed, and the QoS policy queuing, FC mapping, and FC marking are unaffected.
adding QoS match-criteria entries
Adding an additional entry to a QoS policy can lead to a compression failure resulting in an overload condition.
In this case, the newly added entry is not programmed on the affected FP. Additional entries added to the same policy after the first overload condition are also not programmed on the affected FP as the system attempts to install all outstanding additions in order.
The CPM QoS management task controls the maximum number of match criteria entries per FP. If the operator attempts to go over the scaling limit, the system returns an interactive error message.
removing QoS match-criteria entries
Removing match-criteria entries from a QoS policy is always successful.
resolving overload
The overload condition should be resolved by the network operator before adding new entries in the affected policy.
To identify the affected policy, the system logs the overload event providing slot number, FP number, and impacted memory bank. Based on this information, the tools>dump>qos>match-criteria-overload command allows the operator to identify the affected policy and policy entries in the system.
To resolve the overload condition, the network operator can remove the newly added entries from the affected policy or assign a different policy.