Windows 2000 introduces support for IP over ATM. RFC 1577 (and successors) define the basic operation of an IP over ATM network, or more precisely, a Logical IP Subnet over an ATM network. A Logical IP Subnet (or LIS) is a set of IP hosts that can communicate directly with each other. Two hosts belonging to different Logical IP Subnets can communicate only through an IP router that is a member of both subnets.