title: Computer Networks: how do packets find a computer in a network?
body: <p>Suppose I have a computer network, and all computers in this network have the same external IP. The network uses a NAT service to direct packets to specific computers in the network.</p>
  <p>Let's say that one computer in the network sends a packet to a famous website. The packet includes the source IP, which is probably the external IP address and the destination IP (the IP of the website).</p>
  <p>Now, the website returns a response to the external IP address of the network. My question is - once the response has reached the router of the network, how does it know to which computer in the network to send the response? All computers in the network have the same external IP.</p>