1. The means of connecting one location to another for the purpose of transmitting and receiving data. 2. A particular path between two nodes over which data is transmitted. It includes not only the transmission medium, but digital to analog converters, modems, transmission equipment, antennas, etc., associated with this path. In the SDS backbone network, it was a path between two SDS elements. In space these datalinks were microwave or laser. On the ground, they could have been wireline, microwave, or optical fiber.