NAT Routers Part 1: Client Firewalls
Segment 8: Juggling multiple processes
You can simultaneously run several copies of your web browser, speaking with several different web servers out on the Internet simultaneously, using this mechanism. Each will be given a unique and distinct communicating process ID on your PC, so that each client process on your PC can speak with a server process somewhere out on the Internet, with each message finding its own endpoints as appropriate.
All of this happens automatically, so that your NAT router always knows about all of the communicating client processes within your PC, and opens pathways for the responses.
This illustration, then, shows several client processes on your PC accessing server processes out on the worldwide Internet through your NAT router.
As we have explained, client processes in your PC are automatically handled by your NAT router. Because most of the activity done by users of computers on home networks or small office networks are using client processes, this is the usual arrangement for securing those computers using a hardware firewall NAT router. This configuration will automatically handle all of the most popular network tasks that are needed by a typical small office or home office user, including browsers, emailers, many peer-to-peer applications, and client operation of most network games.
As we said earlier, your NAT router always needs help learning about the communicating processes inside your PC that want to receive Internet information. This concludes our discussion of the first of 2 methods that your NAT router uses to learn about communicating processes in your PC wishing to communicate on the Internet.
This automatic method works in behalf of client processes in your PC. It is complemented by a manual configuration mechanism in behalf of any server processes in your PC or PCs. That second, manual mechanism has come to be known as "Port Forwarding", and you can learn more about Port Forwarding from other movies here at AskMisterWizard.com.