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Much attention has recently been given to the Differentiated Services (Diffserv) approach to provide Quality of Service for IP networks. This packet-marking based approach to IP QoS is attractive due to its simplicity and ability to scale. Two of the most popular services proposed for the Diffserv approach are the Assured and Premium Services. In this work, prototypical implementations of Diffserv components are described. The prototypes are used to study the single-queue, dual drop-preference model proposed as a basis for Assured Services in Diffserv. RED (Random Early Detection) is used as the packet discard algorithm in Assured Services. Three different models of RED are experimented with to observe their implications on providing Assured Service. Secondly, experiments are performed to determine service discrimination that can be achieved for Assured Service traffic using this approach. Finally, experimentation was performed to observe the behaviour of real-time low-bandwidth (eg voice) flows that are provided the benefit of an Assured Service.