This read-write Integer32 (-1 to 64800 seconds) sets how long an established TCP session can sit without any traffic before the filter deletes its state and resets both ends. An admin extends this for long-lived idle connections, such as an SSH management session left open overnight, to avoid the filter prematurely tearing it down. For example, if a monitoring system's persistent TCP connection to a remote server keeps dropping after periods of inactivity, raising this idle timeout would keep the session table entry alive longer.