ABSTRACT
The wide diffusion of network address translators (NATs) through the Internet is the result of the increasing demand for hosts capable of communicating across the network although they cannot have routable network addresses due to their shortage in IPv4. The increasing number of mobile devices with wi-fi connectivity has made the demand grow further. The idea behind the NAT is that a restricted minority of the hosts belonging to the same network need to effectively communicate with hosts placed in other networks at any point in time: so assigning a public routable network address to each host of the network is a waste. On the contrary, a NAT dynamically “assigns” a public network address (and port) only to hosts (and applications) at the moment in which they are actually communicating with other hosts in the Internet. By doing this, the number of public network addresses actually required for a subnetwork is reduced (as it is much lower than the number of hosts connected to such a subnetwork), thus rationalizing this precious resource.
