IEEE 802.5r and 802.5j:1997 (R2003)

Amendment Standard - Inactive-Withdrawn.
This amendment to Local and Metropolitan Area Network standard, ISO/IEC 8802-5 : 1998, is part of a family of local area network (LAN) standards dealing with the physical and data link layers as defined by the ISO/IEC Open Systems Interconnection Basic Reference Model. The requirements for dedicated token ring (DTR) operation are specified, including the changes and additions to the Medium Access Control (MAC) layer to provide for an additional full-duplex mode of operation (switching), and for interconnection of shared LAN segments to switch ports. Also specified are the characteristics of a fibre optic interface for connecting a 4 Mbit/s or 16 Mbit/s token ring station to the trunk coupling unit (TCU) of a token ring, including station, port, and channel requirements. Fibre optic trunk signaling recommendations are also made.

Define dedicated attachment of existing token ring stations. In addition, expand the station's capability to simultaneously transmit and receive independent data streams for all frames. define station concentrator functions in sufficient detail to produce an interface between station and concentrator that assures interworking.
As presently defined, each token ring station shares the ring's total available bandwidth. This dedicated attachment extension to 802.5-1995 will provide a significant increase in available bandwidth to each station. Additionally, it will decouple the operating speed of the concentrator from its attaching stations.