This read-create object holds an address mask that, used with busAtmAddrSpec, specifies the portion of the BUS's ATM address desired to be explicitly configured, and setting it likewise reinitializes the BUS and drops all connected clients. This mask lets an operator specify only part of the BUS's address explicitly, letting the switch fill in the rest, such as a prefix assigned via ILMI, but because it triggers the same disruptive reinitialization as busAtmAddrSpec, it shares the same caution about being a provisioning-time rather than live-tuning setting. A mask specifying only the low-order selector byte would let the BUS accept whatever ATM prefix the switch assigns via ILMI while keeping a fixed, operator-chosen selector value for the rest of its address.