A local area network architecture tailored to laboratory environments

A hierarchical local area network architecture is proposed for laboratory process control automation. Coaxial cables are used as communication media and the control of access is totally distributed. Two different arbitration algorithms are implemented in the experimental networks: the first works on a modified algorithm for carrier sense multiple access with collision detection, while the second realizes a low level fast token-passing method. Both arbitration algorithms as well as the logical link control will be described briefly in the paper. Only a connection-oriented logical link service is available. The contention-free multiframe control sequences supported by the physical layer provide a facility to implement a selective flow control, which is applied independently for each logical link.