IEEE standard for MANs (Metropolitan Area Networks). Formerly known as QPSX (Queued Packet and Synchronous Exchange), now known as DQDB (Distributed Queue Dual Bus). It was approved in 1990.

• IEEE关于城域网标准。原来的名称为QPSX（队列分组同步交换），现名为DQDB（分布式队列双总线），1990年获得批准。