Stateful and traditional firewalls can analyze packets and judge them against a set of predetermined rules called access control lists (ACLs). They inspect which of the following elements within a…

Session headers are not a distinct, inspectable packet field; while stateful firewalls track session state internally, there is no packet element called a 'session header' that traditional or stateful firewalls parse against ACLs.

NetFlow is a Cisco traffic-monitoring and reporting technology used for flow telemetry and analytics, not a packet element that firewalls inspect when applying ACL rules.

Source and destination IP addresses and port numbers are the core Layer 3 and Layer 4 fields that both traditional packet-filter and stateful inspection firewalls evaluate against ACL rules to permit or deny traffic. These identifiers reveal which host is communicating, with which destination, and over which service port.

Protocol information such as TCP, UDP, or ICMP is inspected by firewalls at Layer 4 to identify the type of traffic and apply the correct rule set. Knowing the protocol allows stateful firewalls to track connection states appropriately, such as monitoring TCP handshake sequences.