A technology defined by the IEEE 802.6 standard for metropolitan area networks (MANs), as a means of extending the reach of a local area network (LAN) across a metropolitan area.The original work on the DQDB concept was done at the University of Western Australia where it was known as Queued Packet Synchronous Exchange (QPSX). Subsequently, Switched Multimegabit Data Service (SMDS) evolved from these efforts.This technology is considered obsolete. See also 802.6, IEEE, LAN, MAN, and SMDS.