Abstract: A backend data processor of a network monitoring system attempts to identify the point of presence (POP) associated with each uploaded network performance data record by comparing the POP identification information contained in each uploaded data record with the known, valid POP telephone numbers stored in a lookup phone book. A series of lookup searches are performed by comparing a certain number of the digits of the raw POP string with corresponding digits of the POP numbers stored in the lookup phone book until an exact, unique match is found. An initial “pessimistic” lookup search compares the rightmost N digits of the uploaded POP string with the rightmost N digits of each POP number in the lookup phone book for all countries. If the initial pessimistic lookup search is unsuccessful, an optimistic lookup search is conducted taking into account independent information indicating the country code and area code from which the data record originated.