IEEE 802.6-1990

The Standard will define a Dual Bus subnetwork incorporating a shared Medium physical layer of two unidirectioonal buses, a non-isochronous media access control sublayer based on Distributed Queueing and an isochronous media access control sublayer based on centralized time slot allocation. The standard will allow for bridges to interconnect two or more Dual Bus subnetworks to form a Metropolitan Area Network (MAN). The Dual Bus subnetwork and MAN shall be capable both of operating in the public telecommunications network environment and of incorporation in the public network structure, and shall meet the operations, administration, maintenance and performance requirements of this environment for criteria such as reliability, availablity and security. The Dual Bus subnetworks and MAN shall operate at selected rates exceeding 1 Mbps and consistent with public network rates. The Dual Bus subnetworks and MAN shall be capable of operating over areas in excess of 50 kilometers in diameter. The performance and efficiency shall be essentially independent of subnetwork size and rate.

The purpose of the standard is to enable public network providers to offer Metropolitan Area Network service. The services to be provided include telephony, high speed and high quality isochronous service, ISDN access and high speed and high quality packet service such as LAN interconnection, host interconnection, and workstation connection across a metropolitan area. The standard will use the installed and planned base of publioc digital transmission equipment. This will include media such as optical fibre accessed through standard physical interfaces including CCITT G.703.

New IEEE Standard - Inactive-Withdrawn. Withdrawn Standard. Withdrawn Date: Feb 07, 2003. No longer endorsed by the IEEE. This standard is part of a family of standards for local area networks (LANs) and metropolitan area networks (MANs) that deal with the Physical and Data Link Layers as defined by the ISO Open Systems Interconnection Reference Model. It defines a high-speed shared medium access protocol for use over a dual, counterflowing, unidirectional bus subnetwork. The Physical Layer and Distributed Queue Dual Bus (DQDB) Layer are required to support a Logical Link Control (LLC) Sublayer by means of a connectionless Medium Access Control (MAC) Sublayer service in a manner consistent with other IEEE 902 networks. Additional DQDB Layer functions are specified as a framework for other services. These additional functions will support Isochronous Service Users and Connection-Oriented Data Service users, but their implementation is not required for conformance.