Efficient support for scalable multipoint-to-multipoint (mpt-mpt) communication in ATM has recently become a hot topic of discussion at the ATM Forum. Previously, we presented a new class of efficient switch algorithms for point-to-multipoint (pt-mpt) ABR service that deliver high performance in terms of fairness and link utilization and are significantly simpler to implement than other proposed protocols. However, the more challenging problem of providing bidirectional mpt-mpt ABR service has not been addressed before. While a number of key issues have been resolved in unidirectional pt-mpt ABR service, no satisfactory solution for multipoint-point (mpt-pt) ABR service is known. In this paper, we propose new efficient mpt-pt ABR mechanisms that can interoperate with existing standards for ABR service and provide a truly transparent and scalable solution to multipoint communication in ATM. We present simulation results to illustrate that our proposed ABR schemes provide high link utilization and fair bandwidth allocation in a mpt-pt connection for heterogeneous sources with different data rates.

It is known that TCP throughput can degrade significantly over UBR service in a congested ATM network, and the early packet discard (EPD) technique has been proposed to improve the performance. However, recent studies show that EPD cannot ensure fairness among competing VCs in a congested network, but the degree of fairness can be improved using various forms of fair buffer allocation techniques. Based upon the work by H.Y. Tzeng and K.Y. Siu (1996), we propose an improved scheme that utilizes only a single shared FIFO queue for all VCs and admits simple implementation for high speed ATM networks. Our scheme achieves nearly perfect fairness of throughput among multiple TCP connections, comparable to the expensive per-VC queuing technique. Analytical and simulation results are presented to show the validity of this new scheme and significant improvement in performance as compared with existing fair buffer allocation techniques for TCP over ATM.