Recently there has been an enormous growth in the popularity of the Internet. The provisions of access to the Internet will be one of the principal services of the next generation of access networks. In order to provide cost-effective Internet access over ATM-based broadband access networks, the introduction of an available bit rate (ABR) service class is a promising solution. This paper describes our analysis of ABR behavior over ATM-based access networks focusing on explicit-rate-based rate controls and their round-trip time effects. We also describe the hardware implementation of the ABR-based rate controls.