The Distributed Double-Loop Computer Network (DDLCN)

• Authors: Ming T. Liu;Sandra A. Mamrak;Jayshree Ramanathan
• Venue: ACM '80 Proceedings of the ACM 1980 annual conference
• Year: 1980

This paper presents the design of the Distributed Double-Loop Computer Network (DDLCN), which is a local-area distributed computing system that interconnects midi, mini and micro computers using a fault-tolerant double-loop network. Several new features and novel concepts have been incorporated into the design of its subsystems, viz., the reliable communication network, the programming/operating system (P/OS), and the distributed loop data base system (DLDBS). The interface design is unique in that it employs tri-state control logic and bit-sliced processing, thereby enabling the network to become dynamically reconfigurable and fault tolerant with respect to communication link failure as well as component failure in the interface. Three classes of multi-destination communication protocols, each providing a different degree of reliability, have been incorporated into the network to facilitate efficient and reliable exchanges of messages. The P/OS is distinguished from other similar research efforts in that its ultimate goal is to support not only communication and cooperation among autonomous, distributed processes running at various nodes, but also to support convenient and correct resource sharing through program generation (semi-automatic programming) for application and systems programmers. A new concurrency control mechanism for DLDBS has been developed, which uses distributed control without global locking and is deadlock free. In addition to being simple to implement and having good performance (high throughput and low delay), the mechanism is also robust with respect to failure of both communication links and hosts.