The CDR (Call Drop Rate) is the small portion of the telephone calls. These calls, because of technical reasons, were cut off before the talking parties had finished their conversational tone and before one of them dropped calls. Call Drop Rate is usually estimated as a percentage of all calls. A call attempt summons a call setup methodology, if this call is successful then results in a connected call. A connected call might be ended because of a technical reason before the parties making the call. These calls are classified as dropped calls.