Internet Connection Sharing
BITS can force a dial-up connection for home networks that use Microsoft Internet Connection Sharing if Connection Sharing is configured to dial out when computers on the network access the Internet. To prevent a forced dial-up connection, disable the Establish a dial-up connection whenever a computer on my network attempts to access the Internet option on the Connection Sharing host computer that shares its Internet connection.
Computers connected to the Connection Sharing host computer assume they have a network connection, so BITS will try to transfer files. If the dial-up option is disabled on the host computer and the host computer does not have an active connection, the transfers will fail with a transient error. BITS will retry the transfers periodically.