Information
The default time assigned to Access Rules for TCP traffic. If a TCP session is active for a period in excess of this setting, the TCP connection will be cleared by the SonicWALL. The default value is 5 minutes, the minimum value is 1 minute, and the maximum value is 999 minutes.
Note: Setting excessively long connection time-outs will slow the reclamation of stale resources, and in extreme cases could lead to exhaustion of the connection cache.
Solution
Navigate to Firewall Settings->Flood Protection->TCP Settings and check off 'Default TCP Connection Timeout (minutes):'. Set it to a value of 5 or less.