No idea what CIA is, other than a spy organisation ?? However, 'LN' is an abbreviated term (Local Network) that test systems throw out after 'looking' at the line conditions.
IE: The likelihood is the fault will be .................
EX=Exchange
CA= Customer Apparatus
LN= Underground cable
CAL= Customer Apps and Line
So I would suspect CIA is a test system your ISP uses ?? It wasn't CIDT they mentioned, could you have mis-heard ??