The use of an extension to the high level data link control (HDLC) asynchronous balanced mode protocol to provide a reliable satellite data link service which is resilient, without operator intervention, in high levels of noise is described. Research has been directed toward providing a robust data link for the interconnections of stations using a communications satellite. Two mechanisms are described which protect the flow of control information. One is forward error correction of the control portion of the HDLC frames. The other is an extended protocol that employs redundant supervisory frames which are interleaved with the normal link traffic. The implementation of these schemes is outlined. The extended protocol is superior, providing tolerance to a wide range of error environments.