The work we present here reports on the further development and testing of an experimental transport-level protocol. The protocol runs on top of IP, and is intended for mobile, wireless devices. Its central concern is to conserve battery-powered energy used for transmission while maintaining high levels of data throughput. It can be adjusted to achieve higher throughput at the expense of lesser energy saving in accordance with the application's needs. It conserves transmission effort, adjusting data transmission below perceived network congestion level, and thereby minimizes the need for duplicate data retransmission due to congested routers losing packets, and so OIL It achieves high throughput by implementing a network probing mechanism that enables it to investigate instances in which prevailing throughput conditions appear to be deteriorating, before committing to further data transmission. The probing mechanism also permits it to continuously monitor the network during high congestion periods in order to locate windows of sufficiently low congestion opportunity to exploit for transmission