This read-write enumeration (up(1), down(2), write-Only(3)) is used to administratively bring the port up or down; on FRSM12 it is equivalent to the standard ifAdminStatus object in ifTable, and the write-Only value is not actually used. An administrator sets this to down(2) to take the port out of service for maintenance without physically disconnecting it, and back to up(1) to restore it. For example, before performing physical cabling work on a port, an administrator would set portAdmin to down(2) first, then restore it to up(1) once the work is complete.