In this paper, we propose a new cell discarding scheme to improve the cell loss rate in ATM networks. In the proposed scheme, there are two thresholds to control the behavior of cell discarding. When the system is in the heavy traffic situation, we use a low threshold to reduce the cell loss rate of the high priority class, and when the system is in the light traffic situation, we use a high threshold to improve the cell loss rate of the low priority class. According to the analyzed results, the performance of the proposed priority scheme can be better than that of the partial buffer sharing scheme. Besides, the buffer management complexity in the proposed priority scheme is more simple than that of the push-out scheme.

Addition of a second bus is proposed to provide high bandwidth as well as reliable service for token-passing-bus LANs. The second bus proposed is normally used for reservation so that the token on the data bus is dynamically passed to ready users for packet transmission. Furthermore, it takes the place of the data bus when the data bus fails. A reservation token-passing protocol is used which not only is collision-free but also minimizes the token-passing delay. An analysis of this dynamic token-passing protocol includes both analytical and simulation results.>