The next generation of broadband satellites will offer high-capacity digital services to provide high-speed Internet access at low cost, using the terrestrial dial-up infrastructure to provide a return path. The resulting service exhibits significant bandwidth asymmetry and when TCP is used a phenomenon termed 'ACK congestion' is observed. TCP behaviour in an asymmetric network using simulations and both live and emulated test bed experiments is studied. A set of existing techniques to restore performance are analysed and a new technique called 'ACK compaction' is presented and analysed. Although the study focuses on one technology most discussions will be common to any bandwidth-asymmetric network.