How to get notifications when unexpected network disconnection is occurred?

FROM : norio
DATE : Mon Dec 15 12:49:03 2008

I'm sorry to ask you this again.

I don't know if I could have told you my problem correctly, please let 
me tell you again.

1. My app gets NSWorkspaceDidUnmountNotification.
2. Under 10.5, users can handle some actions before the notification 
comes to my app.

I'd like my app to get noticed that a network connection was cut as 
very soon as it occurred.

I don't want to use timer to look at the network port all the time 
while the app runs, if possible.

would you tell me how?

Any suggestion would be very very appreciated.

Thank you,
Norio