1.1 This International Standard specifies the communications operation procedure-1 (COP-1). This procedure is used with the telecommand (TC) space data link protocol (as defined in ISO 22664:2013) to enable the delivery of service data units to the receiving end of the layer above, correct and without omission or duplication, and in the same sequential order in which they were received from the layer above at the sending end. 1.2 This International Standard defines the COP-1 in terms of a) the interfaces with the other procedures, b) the internal variables used by the protocol entity, c) the actions performed by the protocol entity, and d) the state transitions of the protocol entity. 1.3 It does not specify a) individual implementations or products, b) the implementation of service interfaces within real systems, c) the methods or technologies required to perform the procedures, or d) the management activities required to configure and control the protocol. 1.4 The scope and field of application are furthermore detailed in subclauses 1.1, 1.2 and 1.3 of the enclosed CCSDS publication.