This read-only bitmap shows which DS0 timeslots on physical line 2 have already been claimed by logical ports defined so far, with each set bit marking a used DS0 and the most significant byte invalid for a DS1. An administrator provisioning a new port on line 2 consults this bitmap to identify unused DS0s before assigning cesPortDs0ConfigBitMap for the new port. A bitmap showing only a few bits set indicates line 2 still has substantial unused timeslot capacity available for new ports.