Prioritized access in CSMA networks: a node partitioning approach

Abstract

We address the problem of incorporating message-based priority classes in random access protocols. The organization of these classes is based on the different packet delay requirements of higherlayer applications. In this paper, a novel node partitioning mechanism to restrict contention only t o higher priority packets is introduced. We describe node partitioning carrier sense multiple access (NP-CSMA), a protocol that uses CSMA [1,21 as its base access mechanism, and incorporates three priority mechanisms that influence different aspects of the channel access. These are node partitioning, priority queueing a t station buffers, and prioritized persistence. A detailed simulation model i s described. Simulation studies that demonstrate the effect of these mechanisms, separately and in concert, on the throughput and delay of the various priority classes are presented. We show how desired performance can be achieved by suitable variation of protocol parameters.-A large number of local computer networks are based on a broadcast bus topology, which allows full connectivity between nodes a t a relatively low cost. This topology is ideally suited for the bursty traffic typically generated in a local network with many interactive applications.