In packet data transmission, a mode in which there is no call setup phase before transmission begins, no predetermined path set up for frames or packets to travel through a network, and no call teardown phase after transmission ceases.As each packet header contains enough information to enable its independent delivery without the aid of any additional instructions, each packet can take an entirely different route from originating host to destination host. In X.25 networks, for example, datagram service is connectionless. Local area networks (LANs) are connectionless. Internet Protocol (IP) is a connectionless datagram service. See also always on, connection-oriented, datagram service, frame, LAN, packet, and X.25.