A method of monitoring network performance is disclosed and includes receiving a session initiation protocol (SIP) response message from one of a plurality of serving-call session control function (S-CSCF) systems at a centralized error monitoring server of an Internet Protocol (IP) Multimedia Subsystem (IMS). The SIP response message includes at least one error code that matches an error monitoring initial filter criterion included in a subscriber profile. The method also includes sending an alert message to a fault management system of the IMS when at least one threshold related to SIP error codes is met or exceeded based on the at least one error code.