Gx Charging Rules Only Made Sense After I Followed the TFT

A charging rule becomes concrete when its packet filters are followed all the way into bearer treatment.

Gx policy messages were easy to read as configuration objects and hard to connect to packets. The useful change was to follow one rule all the way through: PCC rule, flow description, packet filter, bearer decision, then actual traffic.

A Traffic Flow Template is not a billing label. It describes which packets match a bearer or policy treatment. Direction, address ranges, protocol and port information determine which traffic the rule applies to. If the filter is wrong, the network can create a perfectly valid dedicated bearer that carries none of the traffic I expected.

I started validating rules from both sides. On the policy side I inspected what PCRF delivered. On the EPC side I checked the resulting bearer and TFT. Then I generated traffic that should match one rule and traffic that should not. That simple A/B test caught assumptions about local versus remote ports faster than reading the rule text repeatedly.

The bigger lesson was familiar from routing ACLs: policy is only useful when I can predict the packet match. Telecom names make the objects sound special, but eventually a packet either matches the classifier or it does not.