There have been many improvements to the 3B20D UNIX-RTR system in both software and hardware throughout the 1980s, 1990s, and 2000s. These included some remarkable features such as disk independent operation (DIOP: the ability to continue essential software processing such as telecommunications after duplex failure of redundant essential disks); off-line boot (the ability to split in half and boot the out-of-service half, typically on a new software release); and switch forward (switch processing to the previously out-of-service half). The processor was re-engineered and renamed in 1992 as the 3B21D. It is still in use as a component of many Alcatel-Lucent products such as the 2STP signal transfer point, and the 4ESS and 5ESS switches (both wireline and wireless).