When you get broadband, your internet service provider (ISP) normally supplies you with a broadband modem. This, plus your Mac, is the simplest network you can have, and for lots of people, it’s all the network they need. If you have DSL broadband -- the most common kind -- it’s delivered to your house through the phone line. At the phone socket, you plug in a filter that splits the frequency range so that the lower 4KHz is used by voice phone calls and the rest is sent to the modem.