Lets say that I have a DSL modem and want another computer system to get Lightning DSL, what are the requirements ?

The essential requirement is to network the machines into an IP-based LAN. Once the network infrastructure is in place, a router is needed to allow your private IP network to interact with the public network to which DSL is connected. The router can be an appliance or a piece of software. The first is preferred because appliances offer great functionality with the way your access is shared. If its the latter, the workstation connected to the DSL modem will be the gateway to the entire network and will require TWO network cards. One for the modem and the other for the internal network. In either case, other connecting devices such as hubs, access points or switches may be required. Be aware that the number of workstations connected to your DSL access is a function of performance. Using less than a dozen machines on the Lightning DSL connection is generally understood as an acceptable performance benchmark. You do not want activity on one machine to affect the response time on another ...  more