working principle:
1) on the internal network router connected to the external public network arrives, NAT translates the local internal network address of the internal host, it may appear as a legal address within a global public network to the outside world in response to external addressing.
2) where:
a) Internal or external: reflects the packet source, internal local address and inside global address indicates that the message is from the internal network.
b) partial or full: address indicating the visible range, the local address is visible in the internal network, the global address is visible on the external network.
Way of working:
Internal 1) conversion of a local address; is the external host access to an internal address, corresponding to a valid external IP address.
2) 1 to many overloading inside global address; when is outside access to an internal address of the host, a foreign port number is not valid IP address and a transport layer, respectively.
3) many to many inside global address.