Which firewall component checks the protocol in use to decide whether to allow or deny a packet?

Which firewall component checks the protocol in use to decide whether to allow or deny a packet?

• A. Protocol in use
• B. Interface
• C. TCP code bits
• D. Source IP address

Answer: (A)

Firewalls decide to allow or block traffic by inspecting specific fields in each packet, including the protocol value that indicates what kind of traffic it is (TCP, UDP, ICMP, etc.). The component that checks which protocol is in use is the protocol field itself, which the firewall reads to determine if there’s a rule that permits or denies that type of traffic. Once the protocol matches a rule, the firewall may apply additional checks like ports or addresses. The interface relates to where the packet arrives, not the protocol decision. The source IP address is about who sent the packet, not which protocol it uses. While TCP flags or other header bits can influence rules in some contexts, the fundamental step described—identifying the protocol in use to decide on access—comes from examining the protocol field.

Firewalls decide to allow or block traffic by inspecting specific fields in each packet, including the protocol value that indicates what kind of traffic it is (TCP, UDP, ICMP, etc.). The component that checks which protocol is in use is the protocol field itself, which the firewall reads to determine if there’s a rule that permits or denies that type of traffic. Once the protocol matches a rule, the firewall may apply additional checks like ports or addresses. The interface relates to where the packet arrives, not the protocol decision. The source IP address is about who sent the packet, not which protocol it uses. While TCP flags or other header bits can influence rules in some contexts, the fundamental step described—identifying the protocol in use to decide on access—comes from examining the protocol field.