the termination of Lost-Carrier

e , I want to ask some Termination status some people was terminated because of Session-Timeout some people was terminated because of User-Request some people was terminated because of Lost-Carrier Session-Timeout means he has reached his expiration time User-Request means he request to terminate but what does lost-carrier means? I can't find in freeradius's wiki, but I saw this status in Daloradius and when will the termination be Lost-Carrier? and the user whose termination is Lost-Carrier can't login the next day, the the next next day, he can login again, I don't know why? can somebody figure this out? -- Spacelee