An adaptive token bus protocol for LAN access control

The authors propose an adaptive token bus protocol which aims at improving network bandwidth utilization. The token bus protocol is based on the IEEE 802.4 token bus protocol with an adaptive strategy for soliciting new stations to join the virtual ring, a so-called skip operation for further reduction of the overhead caused by the idle stations in the virtual ring, and a leave-ring operation to avoid a potential additional heavy overhead. Both the adaptive token bus protocol and the IEEE 802.4 token bus standard are implemented on an experimental network of five SUN workstations. The measurements obtained from the experiment show that the adaptive protocol provides a network throughput improvement of up to 15% and a reduction in the network join-ring delay of up to 25%. Better performance can be expected for larger networks with more stations