replacing the BFT, and if you're lower than r4 and want to do a data base conversion, upgrading the software (need to purchase upgrade to 4.0), otherwise it's reprogram from scratch, and migrating the keycodes (has to be done by Avaya). You'll have to return the old BCM400 NSC to Avaya or you will be charged for the migrated keycodes. That's the basic steps, you can get details in the BCM450 upgrade guide.