The differentiated services (DiffServ) framework provides a simple and scalable methodology for addressing quality of service issues in IP networks. Service differentiation can be achieved through the assured forwarding (AF) per hop behavior packet-handling scheme. One of the more challenging research issues in DiffServ networks is the fair distribution of bandwidth among aggregates sharing the same AF class. Several studies have shown that the number of microflows in aggregates, the round trip time, the mean packet size and TCP/UDP interactions are key factors in the throughput obtained by aggregates using this architecture. In this paper, we examine the behavior of a recent technique suggested to improve fairness in a DiffServ network: the Aggregate Flow Control mechanism. We also propose two alternatives in the control overlay of this scheme and compare them with the original approach. Simulation results indicate that our proposed modifications improve throughput assurance and fairness requirements.