Zephyr is a notice transport and delivery system developed at MIT which runs under 4.3BSD Unix.
A Notice Transport and Delivery system is a method of getting small quantities of time sensitive information efficiently from one client (or server) on a network to another. The object is to accomplish this with the highest possible fan-out (i.e., client to server ratio) while maintaining both network and server performance. Zephyr is a multi-cast notice transport and delivery system based upon an authenticated datagram protocol. Localized Zephyr servers provide routing, queueing and dispatching services to clients which communicate with them via the Zephyr Client Library. Two special purpose Zephyr clients, the WindowGram client and the HostManager client provide user and client host communication support.
Zephyrd(8) servers run on designated server machines. These servers maintain a database of subscriptions and locations for every user using Zephyr. The servers stay in contact with one another, and provide a reliable backup system (via duplication) in the event of network failures.
Each client machine on the network runs a zhm(8) HostManager client program which is the link between the Zephyr servers and the users. User programs send notices to the HostManager, and the HostManager forwards these notices to the nearest server for action. The HostManager is responsible for ensuring that the notices reach a server, and for finding a new one if its server fails to respond.
Each user on the network usually runs a WindowGram client program automatically upon login. Zwgc(1) displays notices to the user, and handles user responses. Only notices to which the user has subscribed will be sent to the WindowGram client.
Subscriptions are handled through the zctl(1) program. This program allows the user to add or delete subscriptions from Zephyr, to add the subscriptions to a file, and to perform other miscellaneous functions.
Tony Della Fera (MIT-Project Athena, DEC), Mark W. Eichin (MIT-Project Athena), Robert S. French (MIT-Project Athena), David C. Jedlinsky (MIT-Project Athena), John T. Kohl (MIT-Project Athena, DEC), William E. Sommerfeld (MIT-Project Athena).