This counter increments every time the switch has to resend a TACACS+ authentication Access-Request packet because it didn't get a timely reply, aggregated across every server used for authentication. A rising retransmission count relative to the AccessRequests counter is one of the clearest early indicators of a slow or intermittently unreachable TACACS+ server, well before users start reporting failed logins outright. For instance, a ratio climbing from near-zero to one retransmission for every five requests would point an admin toward network path or server-load issues before an outage occurs.