The 2033 has no H.323 or SIP software - only UNIStim. If you have a 2033 on a "Nortel" system (BCM, CS 1000, CS 2100) and are changing to an "Avaya" system (IP Office, Communication Manager), then you will need to replace the 2033 with a new audioconference unit. Avaya has the 1692 which is H.323-based and the B179 which is SIP-based.