Hybrid Medium Access Protocols for High-Speed, Dual-Bus Fiber-Optic Local Area Networks

Abstract Hybrid access protocols possess the advantages of both the random and the controlled medium access LAN protocols; namely, zero medium access delay at light load and bounded delay at all loads. The paper describes two hybrid access LAN protocols, Z-Net and X-Net, and their performance. The network architecture consists of two, unidirectional fiber-optic buses. A distinct feature of the networks is the use of active taps to minimize the wastage of bandwidth due to collisions. When collisions occur, one transmission continues to completion, while others are aborted. The protocols are distributed and the stations do not require a knowledge of other station locations in the network. Performance results show that high channel utilization can be achieved even when the packet transmission time is low compared to the channel propagation delay. Therefore, the proposed schemes are suitable for operating at high channel data rates and supporting real-time traffic.