The following figure shows how a proxy server can be deployed in an environment. One interface of the router is connected to the internet and the other to the client. When the client requests a connection to the internet, the proxy server receives the requests, checks the request, and repacks the request. As an application-level firewall has information about the packet, they are processor sensitive. These firewalls are also protocol-specific so they use more memory to process a request:

Let's understand how the process works:

1. The proxy server receives a request from the sender/clients
2. The server performs user authentication according to the norms/configurations made into it
3. It forwards Layer 3 and Layer 4 packets to check the rules of the firewall and tries to access the requested website using the internet
4. The proxy server returns the request of the client; the proxy server forwards only Layer 5 and Layer 7 messages and the information allowed by the server

The main reason behind the architecture of application-layer firewalls is solely to provide the highest level of filtering for a specific protocol. Despite everything, the proxy server lowers the speed of network performance since it needs to evaluate the most significant amount of information embedded in packets.