Are you still alive?

What this TCP connection-state interview question tests

This question probes your understanding of TCP keepalive — a foundational mechanism in reliable network communication. Firms building trading systems, market data pipelines, and other latency-sensitive infrastructure need engineers who can reason about connection health and detect silent failures in long-lived TCP streams.

The question asks you to identify and explain the specific protocol-level technique that prevents connections from becoming stale or undetectably broken. A solid answer requires you to distinguish between application-layer heartbeats and the TCP-level mechanism itself, and to understand when and why each matters.

• TCP state machine and connection lifecycle
• Idle connection detection
• Timeout and retransmission behaviour
• Difference between keepalive and application-level probes