Internet Connection Sharing (ICS) is a Windows service that allows one Internet-connected network to share its Internet connection with other systems on a local area network (LAN). ICS routes TCP/IP packets to the Internet from a small LAN. ICS gives NAT services, mapping unique IP addresses of local systems to remaining port numbers in the sharing system. IP addresses on the local computer system are not apparent on the Internet because of the sort of NAT. All packets departing or entering the LAN are transferred from or to the IP address of the additional adapter on the ICS host computer system.