IEEE/ISO/IEC 8802-12-1998

New IEEE Standard - Inactive-Withdrawn.

The media access control characteristics for the demand-priority access method are specified. The layer management, physical layers, and media that support this access method are also specified. Layer and sublayer interface specifications are aligned to the ISO Open Systems Interconnection Basic Reference Model and ISO/IEC 8802 models.

Specifications for 100 Mb/s operation over 100 W balanced cable (twisted-pair) Categories 3 through 5, 150 W shielded balanced cable, and fibre-optic media are included. Optional implementation of redundant links to facilitate automatic recovery of network connectivity in case of link or repeater failure anywhere in the network path is specified. Rules for connecting redundant links within a network are defined.

This International Standard defines the protocol and compatible interconnection of data communication equipment via a repeater-controlled, star-topology Local Area Network (LAN) using the demand-priority access method.

The purpose of this protocol is to provide a higher speed LAN with **deterministic access, priority, and optional filtering**.

Pursuant to this, the protocol will:

• Provide a minimum data rate of 100 Mb/s.
• Provide smooth migration from ISO/IEC 8802-3 and ISO/IEC 8802-5 LANs.
• Support either ISO/IEC 8802-3 or ISO/IEC 8802-5 frame format and MAC service interface to the LLC.
• Support a cascaded star topology over twisted pair and fibre-optic generic building wiring.
• Allow topologies of 2.5 km and greater with three levels of cascading.
• Provide a Physical Layer Bit Error Rate (BER) of less than 10-8.
• Provide fair access and bounded latency.
• Provide two priority levels: *normal* and *high*.
• Provide a low-latency service through high priority for support of multimedia applications over extended networks.
• Support an option for filtering individually addressed packets at the repeater to enhance privacy.
• Support network management to monitor network performance, isolate faults, and control network configuration.
• Enable low-cost implementation and high levels of integration.
• Provide for robust operation by testing the Physical Layer connection before allowing an end node to enter the network, and by removing disruptive nodes.
• Support an option for redundant links that will enable automatic recovery of network connectivity in case of link or repeater failure anywhere in the network path.