IEEE 802.6 is a standard governed by the ANSI for Metropolitan Area Networks (MAN). It is an improvement of an older standard (also created by ANSI) which used the Fiber distributed data interface (FDDI) network structure. The FDDI-based standard failed due to its expensive implementation and lack of compatibility with current LAN standards. The IEEE 802.6 standard uses the Distributed Queue Dual Bus (DQDB) network form. This form supports 150 Mbit/s transfer rates. It consists of two unconnected unidirectional buses. DQDB is rated for a maximum of 160 km before significant signal degradation over fiberoptic cable with an optical wavelength of 1310 nm. The American National Standards Institute or ANSI (pronounced an-see) is a nonprofit organization that oversees the development of standards for products, services, processes and systems in the United States. ... Metropolitan area networks or MANs are large computer networks usually spanning a campus or a city. ... In computer networking, fiber-distributed data interface (FDDI) is a standard for data transmission in a local area network that can extend in range up to 200 km (124 miles). ... Local area network scheme A local area network (LAN) is a computer network covering a local area, like a home, office, or group of buildings[1]. Current LANs are most likely to be based on switched IEEE 802. ... In telecommunication, a distributed-queue dual-bus network (DQDB) is a distributed multi-access network that (a) supports integrated communications using a dual bus and distributed queuing, (b) provides access to local or metropolitan area networks, and (c) supports connectionless data transfer, connection-oriented data transfer, and isochronous communications, such...

This standard has also failed, mostly due to the same reasons that the FDDI standard failed. Most MANs now use Synchronous Optical Network (SONET) or Asynchronous Transfer Mode (ATM) network designs, with recent designs using native Ethernet or MPLS. It has been suggested that this article be split into articles entitled synchronous optical networking, SONET and SDH. (Discuss) Synchronous optical networking, is a method for communicating digital information using lasers or light-emitting diodes (LEDs) over optical fiber. ... Asynchronous Transfer Mode (ATM) is a cell relay, network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ... Ethernet is a large, diverse family of frame-based computer networking technologies for local area networks (LANs). ... MPLS is a common abbreviation for Multiprotocol Label Switching. ...