When you first drop a wireless router into your house, you create a local area network (LAN). For most folks, the purpose of the LAN is to give each device in the house access to the Internet via your wide area network (WAN) provider. The LAN device talks to your cable modem, DSL device, or other hardware that connects you to the WAN and then the 'net itself. Facilitating traffic among the devices within the house is generally not considered.
It should have been easy. I cleaned up some longstanding music organization issues on my notebook and started iTunes to let it catch up. It wound up creating duplicate entries for several hundred songs -- marked as unavailable, but duplicates nonetheless. It turns out there's no easy way to tell iTunes to remove deleted files from the library. This guy has it figured out.