The University of British Columbia

This paper proposes and analyzes a preemptive reservation arbitrated access scheme to facilitate the transport of real time traffic over dual bus metropolitan area networks (MANs) on a bandwidth on demand basis. This access protocol allows full statistical multiplexing among variable bit rate isochronous (VBRI) traffic while providing nearly isochronous transport service thus enabling significant capacity improvement compared to pre-arbitrated (PA) access. We have analyzed its performance by simulations validated by idealized analytical results. Results indicate that at the expense of requiring one more control bit in the access control field (ACF), preemptive RA access provides much fairer service than the 1-persistent RA access scheme. It is also not too sensitive to propagation delay unless the delay is unrealistically high. In general, RA access offers a valuable complement to the existing PA and queue-arbitrated (QA) access methods to provide a complete set of transport solutions for all B-ISDN services