IEEE 802.5c-1991

Section
1 Overview
1.1 Introduction
1.2 Definitions
1.3 Abbreviations and symbols
2 Dual ring station definition
3 Dual ring reconfiguration
4 Dual ring management function
4.1 Dual ring management function inputs
4.1.1 Break indication
4.1.2 MAC insert control indication
4.1.3 Active monitor present indication
4.1.4 Receive beacon reconfigure indication
4.1.5 Receive beacon normal indication
4.1.6 Transmit beacon reconfigure indication
4.1.7 Management interlock flag (MIF) value
4.1.8 Merge permission flag (MPF) value
4.2 Dual ring management function variables
4.3 Dual ring management function timers
4.4 Dual ring management function finite state
       machine
4.4.1 State D0: PASS
4.4.2 State D1: NORMal
4.4.3 State D2: TPWBNR
4.4.4 State D3: RBPWRS
4.4.5 State D4: TSWBNR
4.4.6 State D5: WRAPB
4.4.7 State D6: WRAPA
4.4.8 State D&: ISOLated
4.5 Dual ring management function outputs
5 Management interface
5.1 Station management interface
5.1.1 Parameters
5.1.2 Events
6 IEEE 802.5 MAC finite state machine (FSM) changes
       for dual ring stations
6.1 MAC inputs
6.1.1 MAC break flag
6.1.2 MAC transmit BNR enable flag
6.2 Changes to the standby monitor FSM
6.2.1 Additional standby monitor state/variable
6.2.2 New/modified standby monitor FSM state
       transitions
6.3 Changes to the active monitor FSM
Figure
Fig 1-1 Dual ring architecture
Fig 1-2 Failure recovery by wrapback
Fig 2-1 Dual ring station functional partitioning
Fig 2-2 Dual ring crosspoint function abstract
         definition
Fig 2-3 Dual ring crosspoint function abstract
         definition in WRAPA state
Fig 3-1 Dual ring wrapback scenario diagram
Fig 4-1 DRFSM inputs/outputs
Fig 4-2 Frequency error detection criteria
Fig 4-3 DRFSM transition diagram
Fig 6-1 Modified/new standby monitor FSM transitions
Fig 6-1 Modified/new active monitor FSM transitions
Table
Table 4-1 DRFSM transition diagram legend
Table 4-2 DRFSM outputs

Defines extensions to IEEE 802.5 which implements a Dual Ring LAN topology having the following features: Full interoperability between stations conforming to IEEE 802.5, including coexistence on the same ring; recovery from all single media failures with full capability restored. Coverage includes: abbreviations and symbols; dual ring management function variables; dual ring management function outputs; station management interface. Also gives definitions, diagrams and tables.