A dynamically-enforceable application-controlled quasi-reliable extension to TCP permits a client application to dynamically set a percent loss tolerance for data transmission reliability through network input/output system calls to the TCP, thereby programming the transport layer to optimistically acknowledge non-critical missing frames. The reliability requirement can be dynamically set within TCP to the level of reliability required for specific data frames within the data stream during the data transfer. Based on this loss tolerance specified, the TCP layer makes a determination whether to trigger a retransmission or continue delivering out-of-order frames to the application. A forced acknowledgement frame is sent for each missing packet until the number missing packets causing forced acknowledgments within the current receive buffer frame exceeds the loss tolerance. This process avoids needless retransmissions and permits the TCP data flow and sliding window to advance uninterrupted, thereby providing substantial performance benefits to network throughput.