Design of a High-Speed Word-Switched Transport Station

A MININET "station" acts as a user concentrator into the MININET word-switched network where each word (of up to 16 bits) entering a network "port" is mapped into a single packet for immediate transmission through the network. The stations maintain highly transparent "virtual connections" between user devices. Among the important requirements for MININET are that, under saturation conditions, the communication resources of the network be shared fairly between the user devices and that the network possesses very short end-to-end propagation delays. The design of a station meeting these requirements, capable of processing over one million packets per second, is described. Its architecture is based on special-purpose processors which are functionally distributed. The biggest design challenge was to minimize the processing delay in the node while avoiding potential blockages and remaining fair. The final solution has been to use a master arbiter, which looks at the readiness of the ports and channels in conjunction with connection, routing, and flow control information. The station management entities reside in a general-purpose microcomputer. These monitor and modify the operation of the high-speed processors, establish virtual connections, and support the routing algorithm.