en technology and the legal right to, or public expectation of, privacy in the collection and sharing of data. data link (1) The equipment and rules (protocol) used for sending and receiving data. (2) Any serial data communications transmission path, generally between two adjacent nodes or devices and without any intermediate switching nodes. data link layer OSI Layer 2, which defines how data is packetized and transmitted to and from each network device. It is divided into two sublayers: Media Access Control (MAC) and Logical Link Control (LLC). The MAC layer controls access to a communications link and shares it among many users, while the data link layer uses procedures and protocols to carry data across the link. The data link layer also detects and corrects transmission errors. data management Provision of access to data, monitoring or storage of data, and control of input/output devices. data PBX A switch that enables a user on an attached circuit to select from other circuits, usually one at a time and on a contention basis, for the purpose of establishing a through con- nection. A data PBX is distinguished from a PBX in that it supports data transmission and not voice. data rate The speed at which a channel carries data, measured in bits per second (bps). data service A digital service offered for data communications at subscriber locations. data set An infrequently used term for a modem. data-switching exchange The equipment installed at a single location to provide switch- ing functions, such as circuit switching, message switching, and packet switching. data system A system for the storage and retrieval of data, its transmission to terminals, and controls to provide adequate protection and ensure proper usage. data transmission The movement of information from one location to another by means of some form of communication media. datagram A message of fixed maximum length, sent without network-provided facilities for assuring its accuracy, delivery, or correct sequencing with respect to related messages