Stateful Firewalls Also called stateful packet filters and application-aware packet filters.
{"Image DocumentName": "Stateful FirewallsAlso called stateful packet filters and application-aware packet filters.", "Image ImageDescription": "Stateful firewalls have two main improvements over packet filters: They maintain a session table (state table) where they track all connections. They recognize dynamic applications and know which additional connections will be initiated between the endpoints. The state table, or session table, is part of the internal data structure of a stateful packet filter. The table tracks all the sessions and inspects all the packets that pass over the stateful packet filter firewall. The packets only pass if they have the expected properties that the state table predicts. The state table dynamically changes and adapts with the traffic flow. If no state exists, a state is created and entered into the state table if the traffic flow meets the rules allowed in the firewall. Stateful packet filters are application-aware through additional inspection of passing traffic. By inspecting the session more closely, up to the application layer, a stateful packet filter is able to associate any dynamic channels of the application with the initial session of the application. The concept of a session in the stateful packet filter world is connected to the TCP and UDP notion of a session. Some stateful packet filter implementations, however, can keep the state of other protocols, such as the Internet Control Message Protocol (ICMP) or generic routing encapsulation (GRE).", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}