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We compare policies that offer differentiated services to TCP traffic. Specifically, we study the effectiveness of scheduling and buffer management policies on the performance of competing TCP connections. In class-based priority services, packets/connections can be given time priority or space priority. Time priority policies aim to reduce delay, as done through scheduling. Space priority policies reduce losses and include buffer management policies. In this work we consider a packet-based weighted-fair-queueing scheduling policy where packets of different classes are scheduled according to their pre-assigned static weight. The three buffer management policies used are complete sharing, complete sharing with pushout at various threshold, and complete partitioning. We consider two long-life TCP connections at a bottleneck node. We study the relative effectiveness of the mentioned priority policies by comparing the performance of the TCP connections. Performance measures of interest are TCP throughput, loss probability, and average delay. We come to some insightful conclusions as to which policies have the most effect, and how the appropriate parameters may be chosen to achieve the required level of differentiation.
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