Issues insufficiently resolved in Century 20 in the fault-tolerant distributed computing field

As the 21st Century has just opened up, it is a fitting time to reflect on the evolution of the fault-tolerant distributed computing technology that occurred in the last century. The author's view of that evolution is sketched in this paper, with emphasis on the major issues that were insufficiently resolved in the 20th Century. Such issues are naturally among what the author believes to be the prime subjects that need to be addressed in this decade by the research community. A substantial part of this paper deals with the issues that need to be resolved to advance the real-time fault-tolerant distributed computing branch into a mature practicing field.