Interprocess communications in the AN/BSY-2 distributed computer system: a case study

This paper presents a case study of the design and implementation of the interprocess communications facility developed for the AN/BSY-2 distributed computer system, the computer system for the Seawolf submarine. The interprocess communications facility was identified as a critical design challenge for the AN/BSY-2 system, as the system incorporated new component and network technology along with new run time system services as well as application programs. The requirements specified for the interprocess communications included aggressive performance, as well as functional capabilities that had not been previously fielded. The AN/BSY-2 computer system is comprised of over 100 processors interconnected in multiple fault tolerant fiber optic rings. First, a description of the AN/BSY-2 distributed architecture is presented. The message-passing semantics are then presented. A key feature of the IPC facility is it’s support for both synchronous and asynchronous communications based on logical addressing. Logical addressing within the AN/BSY-2 system supports point to point as well as group communications, and also supports the fault tolerant requirements of the system. The hardware developed to support fast real time messaging, and support fault tolerance is discussed. Finally, the low level semantics of a message transfer through the system is outlined.