Today Microsoft gave more details on the Xbox One's connectivity requirements.

The system can be played offline "for up to 24 hours" on your primary console or up to one hour if you're using your login on somebody else's system. Although you can use your Xbox One for other stuff (to watch live TV or play movies) while offline, you cannot play games offline after the allotted time unless you reconnect. The company says this is to see if "you have acquired new games, or resold, traded in, or given your game to a friend," as well as for system, app, and game updates. It would appear that this is the method by which Microsoft will determine if you've given/sold your game to someone else.

Microsoft also recommends a broadband connection of 1.5Mbps for the best experience with the system, and that if you don't have Ethernet, you can tether the system to your phone's broadband (provided your provider allows it).

Here's the info direct from Microsoft:

To ensure Xbox One works optimally and can offer the experiences described above, it is designed with the following networking requirements:

For an optimal experience, we recommend a broadband connection of 1.5Mbps. (For reference, the average global internet connection speed as measured recently by Akamai was 2.9 Mbps). In areas where an Ethernet connection is not available, you can connect using mobile broadband.

While a persistent connection is not required, Xbox One is designed to verify if system, application or game updates are needed and to see if you have acquired new games, or resold, traded in, or given your game to a friend. Games that are designed to take advantage of the cloud may require a connection.

With Xbox One you can game offline for up to 24 hours on your primary console, or one hour if you are logged on to a separate console accessing your library. Offline gaming is not possible after these prescribed times until you re-establish a connection, but you can still watch live TV and enjoy Blu-ray and DVD movies.

In addition, Microsoft offered details today on how the Xbox One will address used game sales and game sharing with friends, and offered clarifications regarding the upcoming console's privacy settings.

[Source: Microsoft]