Аннотация:The paper is devoted to the problems of guaranteed data transmission with a dynamically changing amount of packet loss ranging from 0 to 23% in channels with a bandwidth of more than 0.5 Mbps. The problems arising due to standard TCP loss protection mechanisms, such as retransmit flows and buffer overflows are considered. Mechanisms for recovering data and service information, tuning for the current state of the channel are proposed, the implementation of the adaptive protocol of the data link layer is described, and the results of its operation are presented. It also describes the operation of a separate protocol subsystem for low-speed channels starting from 1200 bps.