The AppleTalk Control Protocol (ATCP) is used to establish and configure AppleTalk over the Point-to-Point Protocol
(PPP). The ATCP protocol is responsible for the configuration, release and locking of protocol modules, at both connected stations of a PPP connection. The ATCP protocol uses the same exchange mechanisms for the data packets as the Link Control Protocol (LCP). The exchange of data packets can only take place when the PPP connection is established. Data packets that are transferred before this are discarded.