State

Many network failures look like “the service never started”, “the port is not listening”, or “the peer did not reply”. When you keep tracing them, you often discover a firewall policy boundary in the middle. The application thinks it is only connecting to 443. Operations thinks only one security-group rule was opened. The user thinks “if ping works, access should work too”. In reality, the traffic is often being judged by a device or host in the middle that decides whether this flow is allowed to pass.