Implementing a layered network protocol using Occam and transputers

Transputers have only slowly penetrated their main marketplace-the embedded systems field-partially due to the lack of large-scale support modules to interconnect with the processors. One area still not adequately addressed is the need for high-speed communication to and from conventional architectures and centralised filestores. The paper describes the author´s work on direct local area networking facilities for transputers, to make their applications accessible from an Ethernet network. This will permit experiments to be controlled from graphics workstations, data to be stored to networked fileservers, and multiple users to be able to access a pool of transputers from conventional networked terminals. A transputer must provide the basic physical layer interface to the communications medium, and higher-level services must be distributed around the other transputers, allowing some or all of them to support application-layer processes. The author is using a ternary tree-like structure to provide a maximum number of connections using transputers with four links. The Ethernet interface is provided by a T414 transputer with 2 Mbytes of dynamic memory, as well as 128 Kbytes of static memory shared with an Ethernet controller circuit. The TCP/IP networking protocol is being implemented and the author has designed and implemented the various layers as separate Occam processes