A Performance Evaluation of Buffer Management and Scheduling for ATM- GFR Using TCP

Among the various categories of ATM (Asynchronous Transfer Mode) service, ABR (Available Bit Rate) and UBR (Unspecified Bit Rate) have been introduced to support data traffic (such as TCP). GFR (Guarantee Frame Rate) is the current proposed ATM service to provide better performance for data traffic over ATM. The aim of this paper is two-folded. Firstly, we characterise the major research issues in GFR and draw upon the published works to illustrate some of the critical issues about the specification and the possible alternatives of its implementation. Secondly, we undertake a performance evaluation of ATM-GFR’s buffer management algorithms (two-static-threshold scheme and per-VC accounting) and scheduling (FIFO (First In First Out) and WFQ (Weighted Fair Queue)). The simulation results have shown that two-static-threshold-buffermanagement and per-VC-buffer management give the best performance comparing with plain UBR, UBREPD and per-VC scheduling. We also found that the two-threshold buffer management scheme is significant to handle CLP0+1 traffic. This scheme can distinguish between the tagged (low priority) and untagged (high priority) packets of the traffic and protect the bandwidth from flushing by tagged packets. The per-VC scheduling without the sensitivity of tagged/untagged frames can lead to the poor performance for untagged (high priority) packets.