Counts TCP connections that transitioned directly from SYN-SENT or SYN-RCVD to CLOSED, plus those that fell back from SYN-RCVD to LISTEN, meaning connection attempts that failed to complete the handshake. For connections the gateway itself initiates or listens for, a rising tcpAttemptFails points to a peer refusing or timing out the handshake, useful for spotting a management-plane service, like a log server, that's become unreachable even though the gateway's basic network path is fine. Example: tcpAttemptFails rising specifically for the gateway's connections to its configured update server, while other outbound connections succeed, isolates the problem to that one peer rather than the network path in general.