In this paper, we consider the configuration of control parameters with a DiffServ node, with our focus particularly on the configuration for the AF-TCP class. Simulations are carried out to examine the appropriateness of various configurations. It is observed that, while the total throughput of all the users generally increases with the value of the maximum dropping threshold for the Yellow-marked packets (those that are deemed non-conforming to the committed data rate), sensitivity to the threshold configuration is not very significant due to the robustness of TCP's congestion control mechanism. On the other band, we also observe that the unfairness between the users, in terms of the ratio of the achieved throughput versus the target, can be significantly improved by setting the bucket size of the policing token bucket to a value that matches the maximum RTT (round trip time).
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