Layer 3: Represents where delivery of network traffic on Wide
Area Networks (WANs) or more commonly, the Internet, takes
place; addressing in this layer is referred to as Internet Protocol
(IP) addressing, and creates unique addresses, except when
Network Address Translation (NAT) is employed. Network
Address Translation makes it possible to address multiple physical
systems by a single layer 3 IP address. An example of a physical
device performing in this layer would be a router