When this pseudowire's role is secondary, this field names the primary pseudowire it protects, letting an admin immediately identify the paired working PW without cross-referencing the whole PW table by role and customer. This is only meaningful on secondary PWs; on a primary or stand-alone PW this field presumably has no relevant value. If cienaCesMplsPwBlocking shows this secondary PW is now forwarding, no longer blocking, the primary PW named here is the one an admin should immediately go check for the failure that triggered the switchover.