Transparent network data connectivity is a critical underlying technology for the development of distributed control systems. The Network Data-Delivery Service (NDDS) makes it easy to share data and event information among distributed systems. With a few simple calls, real-time programs can send and receive automatic data updates with NDDS's subscription facility, or query for data anywhere on the network. The NDDS system makes intelligent distributed systems practical.
NDDS is flexible and robust. Its quasi-stateless protocol naturally handles communications failures and network changes. NDDS is symmetric; there are no ``special'' nodes nor name servers. Multiple consumers can simultaneously access data from anywhere in the system. Multiple producers are automatically arbitrated. Data sources and sinks-and network configurations-can be modified dynamically while the system is in operation. Both ``best effort'' and reliable updates are fully supported.