Our first topology exists as a drop-in replacement for the many NAT firewalls that exist in the market. In small offices and homes, solutions such as the embedded NAT firewalls sold by D-Link, Linksys, and friends are frequently deployed in order to provide small networks with cost-effective Internet access. Solutions such as Internet Connection Sharing (see http://www.microsoft.com/windowsxp/ using/networking/learnmore/default.mspx for more information on Internet Connection Sharing from Microsoft), a combined NAT firewall, DNS Proxy, and DHCP Server, built into client editions of Windows since Windows 98, are also frequently used in order to allow one PC with a modem or network interface to act as a network gateway for other clients. For our purposes here, we will consider ICS, as such a topology with ICS is effectively a superset of the work required to replace a router such as a Linksys or NETGEAR model as mentioned previously Our migration from one...