Abstract LANSF is a software package that was originally designed as a tool to investigate the behaviour of medium access control (MAC) level protocols. These protocols form an interesting class of distributed computations: timing of events is the key factor in them. The protocol definition language of LANSF is based on C, and protocols are specified (programmed) as collections of communicating, interrupt‐driven processes. These specifications are executable: an event‐driven emulator of MAC‐level communication phenomena forms the foundation of the implementation. Some tools for debugging, testing, and validation of protocol specifications are provided. We present key features of LANSF at the syntactic level, comment informally on the semantics of these features, and highlight some implementation issues. A complete example of a LANSF application is discussed in the Appendix.

A collision protocol called piggyback Ethernet which is applicable for fast bus-type networks based on single, uniform, unsegmented, broadcast-type carriers is presented. Although piggyback Ethernet assumes that each station possesses certain global knowledge about the geometry of the network, it is argued that this knowledge can be acquired automatically at a reasonably small expense. The performance of the protocol for very heavy traffic is not worse than the performance of other protocols operating in a completely synchronized manner. The advantage this solution is its very good performance for light loads which is, for practical purposes, not worse than the performance of Ethernet. Moreover, compared to other protocols for fast networks, piggyback Ethernet has quite modest hardware requirements. The network is based on a straightforward bidirectional cable, each station has only one connection to the bus, and the actual length of the carrier is not bigger than the maximum distance between two stations.>

A formal semantics of a model for a communication channel is given. The model is the foundation of a simulation package which can be used for modeling of communication phenomena in distributed physical systems. The software system based on the model can be viewed as an emulator for LAN-type communication networks. The approach is centered around a formal model of s single CSMA/CD communication channel. The proposed model reflects all relevant elements of a real channel at the medium access control level.>

The performance of the ENET II protocol is discussed and compared to the performance of the commercial Ethernet. Linear network topologies with various number of stations uniformly distributed along the bus are considered. The comparison is based on extensive simulation studies and a recently published performance analysis of ENET II by Y.-C. Liu and G.L. Wise (1987). The experimental results agree with the analysis by Liu and Wise, but they do not confirm the results of M.K. Molloy (1985).>