The main source of slavery in this part of the world in the Middle Ages was indebtedness. In China, impoverished peasants frequently sold members of their own families into slavery, and throughout the entire medieval period criminals or members of their families became slaves of the state.
Nonetheless, NAT can introduce complications in communication between hosts.     * NAT(Network Address Translation) is most commonly used by broadband routers. NAT allows the router to assign non-publically routable IP addresses to the computers on the network.
To check for double NAT on your network, log into your router and look up the IP address of its WAN port. If you see an address in the 10.x.x.x or 192.168.x.x range (both of which are private) it means that the device your router's WAN port connects to is doing NAT, and hence, you're dealing with double NAT.