What is the minimum ICAO Language Proficiency rating required for an air traffic controller providing international air traffic services, and what is the re-evaluation interval for that level?

1. Level 3 (Pre-operational), re-evaluated every 2 years
2. Level 5 (Extended), re-evaluated every 4 years
3. Level 6 (Expert), re-evaluated every 5 years
4. Level 4 (Operational), re-evaluated at least every 3 years