Final answer:
A packet filter gateway, also known as a firewall, works at the network or transport layer of the TCP/IP model. It examines each packet of data and uses pre-determined rules to decide if it should be allowed through or blocked.
Step-by-step explanation:
A packet filter gateway, also known as a firewall, works at the network layer or the transport layer of the TCP/IP model. It examines each packet of data that enters or leaves a network and uses a set of pre-determined rules to decide whether to allow or block the packet.
For example, a packet filter gateway can analyze the source and destination IP addresses, port numbers, and protocol types to determine if a packet should be allowed through. This filtering capability helps protect a network from unauthorized access and potential security threats.
Overall, a packet filter gateway operates at a lower layer than application gateways or proxy servers, which work at the application layer of the TCP/IP model.