About Heartbeats

When heartbeat packets are sent to an inline tool, they are expected to be received back when the inline tool is healthy. Negative heartbeat packets complement heartbeat packets to verify the health of inline tools. When negative heartbeat packets are sent to an inline tool, they are not expected to be received back when the inline tool is healthy.

When some inline tools begin to fail, they allow packets though that should have been dropped. A negative heartbeat detects such a failure by sending a packet that should not pass through an inline tool. If the negative heartbeat packet passes through an inline tool, the tool is deemed to have failed. Therefore, a negative heartbeat packet received back from an inline tool indicates a tool failure.

Heartbeat packets and negative heartbeat packets can be used in any combination: heartbeat only, negative heartbeat only, neither, or both.