Hi,

Microsoft has a feature called 'Network Connecitivity Status Indicator' (NCSI), with which it determines if the current network requires additional authentication (e.g. a WiFi network requiring login).

http://technet.microsoft.com/en-us/library/cc766017%28WS.10%29.aspx

http://blog.superuser.com/2011/05/16/windows-7-network-awareness/

Above are two references to how it works.

In essence:

 - perform a DNS lookup for a well-known domain; then perform a HTTP get
 - perform a DNS lookup for another well-known domain.

Knowing what the results are you can determine if the network provides unrestricted DNS resoultion, or unrestricted access.

It would be nice if this feature was in Network Manager (ideally, there would be a discrete signal to indicate 'network-connectivity', 'network-limited' and 'network-completely-available' -- names made up).

The rational for discrete signals to indicate success transition to a fully connected network state is so that so not every program will attempt connections whilst the network requires authentication (e.g. pidgin, evolution).