|  |  | Circuit Level gateways validate TCP and UDP sessions before opening a session or circuit through a firewall. Once the request has been verified, the circuit level gateway stores the session information in a table for future use and verification. All traffic matching the information in the table is then allowed to pass without further inspection. When the session ends, its information is removed from the table and the circuit is closed. A new session will be verified before traffic is allowed to enter the network.