One of the most important factors to be considered for capacity planning with PCC rules is the number of unique policies that are applied to subscribers.
A unique policy constitutes a base a QoS policy or filter ID along with all PCC rules that are applied to a subscriber or a set of subscribers.
Now examine an example where there are ‛n’ PCC rules in the system (‛n’ qos rules and ‛n’ ACL filter rules). Those rules are applied to IPv4 traffic in ingress direction. Further, assume that the PCC rules do not have defined Precedence AVP, which means that the system can optimize their order for maximum sharing and maximized scale. Then, ‛n’ PCC rules can be combined by various permutation into 2^n-1 unique combinations Next assumption is that there are five possible base qos-policies for IPv4 traffic in ingress direction and five possible base filters for IPv4 traffic in the ingress direction.
Given the above, the unique PCC rule combinations (2^n-1) together with five base QoS polices produce 5*(2^n-1) unique qos-policies per ingress IPv4. Same logic can be applied for ingress IPv4 filters.
This exercise must be repeated for egress direction as well as for IPv6 type traffic, by taking into consideration the number of respective base qos-policies/filters and the number of PCC rules.
When the number of unique policy combinations is determined and ensured that it is within the system limits, each policy must be further evaluated to determine the number of entries it takes in CAM.