Start with the service
Design tests for registration, session establishment, QoS, mobility, congestion, failure, recovery and observability.
Write the application outcome, affected users or devices, geographic area, traffic profile and failure consequence before choosing a technical mechanism.
Separate requirements from mechanisms
Latency, availability, privacy, addressing, reachability, mobility and cost are requirements. A slice, private APN, VPN, local UPF or private network is a mechanism. More than one mechanism may satisfy the same requirement.
Demand observable evidence
Every material promise should map to a test, telemetry source, owner and acceptance threshold. Avoid relying on unqualified terms such as guaranteed, isolated, prioritised or ultra-low latency.
Plan lifecycle and change
Include firmware updates, SIM replacement, device certification, network upgrades, coverage changes, contract renewal and application migration in the operating model.