Abstract: A method of automatically adjusting the line speed for communication between a client having data communications equipment (DCE) and a server having data terminal equipment (DTE). A first connection is established between the client and the server at a first speed, and the client sends a first synchronous data link control (SDLC) frame that identifies a requested speed. The server than sends a second SDLC frame in response to the first SDLC frame, identifying a second speed, wherein the second speed is the smaller of the requested speed and a predetermined (maximum) speed. If the client determines to communicate at the second speed, it drops the first connection, establishes a second connection at the second speed, and sends a third SDLC frame at the second speed; the server then sends a fourth SDLC frame in response to the third SDLC frame at the second speed, to confirm the connection, and data transmission follows.