"When the user client process sends a message, the proxy firewall runs a server process to receive the request. The server (I said it is the HTTP proxy )opens the packet at the application level and finds out if the request is ligitimate. If it is, the server acts as a client process and sends the message to the real server (I said it is the HTTP Sever) in the corporation. If it is not, the message is dropped and an error message is sent to the external user. Figure 31.11 shows a proxy firewall implementation".
If that didn't happen, all this crap would be hitting your HTTP proxy and slowing your system down. The firewall is designed to deny unauthorized access.
Did you mean the firewall that filter packet relying on layer 3 and layer 4....if this is what you meant, I have got no problem with that.
But my concern is , if the device in the figure which is called "Proxy firewall" is filtering packets relying on layer 7 (application layer),,,that means it will do the same job for HHTP proxy,,,,,Am I right ?
If you agree with me that means I have got two separate devices are doing the same jobs,,!!!!