Properties of BuST and timed-token protocols in managing hard real-time traffic

Token passing channel access mechanisms are used in several communication networks. An important class of token passing approaches are the so-called timed token protocols, which are able to manage both real-time traffic and non real-time traffic. Recently, a new token passing protocol, called Budget Sharing Token protocol (BuST), was proposed to improve the existing timed token approaches in terms of real-time bandwidth guarantee. This paper analyzes the ability of BuST to manage real-time and non real-time traffic under three different budget allocation schemes, and compares the performance of BuST with the original timed-token protocol (FDDI) and its modified version (FDDI-M). It is shown that BuST provides an higher guaranteed bandwidth for real-time traffic than FDDI, and improves the service for non real-time traffic with respect to FDDI-M. Moreover, new properties of the analyzed budget allocation schemes are provided for BuST, FDDI and FDDI-M. Finally, a set of simulation results are carried out to assess the performance of the three considered protocols.