International Business Machines Corporation

3com Corporation

Jay L Smith

Anthony D Walker

Bradley S Trubey

Robert B Hobgood

Nai Po Lee

Kenneth T Wilson

David E Bartolini

Robert D Verne

An apparatus and method for fault isolation and bypass in a dual ring communication system provides a reconfiguration unit capable of attachment to a dual ring communication system having a plurality of reconfiguration units. The disclosed reconfiguration unit has a single adapter to the dual ring communication system and includes isolation and wrap switches capable of isolation and bypass of faults. A reconfiguration unit having a single adapter to the dual ring communication system detects failures on the ring and generates a failure frame which if not received from the ring causes the reconfiguration unit to enter a downstream wrap state. The reconfiguration unit enters an upstream wrap state if a failure frame is received from the nearest downstream reconfiguration unit.

Methods and systems for fault isolation and bypass in a dual ring

Methods and systems for determining the address of the nearest downstream reconfiguration unit in a dual ring communication system. In a dual ring communication system having a plurality of reconfiguration units one of the reconfiguration units determines if a Reconfiguration Unit Monitor is active on the system. If a Reconfiguration Unit Monitor is not active the reconfiguration unit requests and stores address information from the remaining reconfiguration units in the ring and assembles a ring sequence reconfiguration unit ring map. The reconfiguration unit transmits the reconfiguration unit ring map to the remaining reconfiguration units in the ring. Reconfiguration units receive the reconfiguration unit ring map from the Reconfiguration Unit Monitor and extracts the address of the nearest downstream reconfiguration unit from the reconfiguration unit ring map.

Method and systems for determining the nearest downstream

In a serial network which includes a hub having a plurality of ports each for attaching one or more stations a mechanism for correlating a list of stations developed in a poll cycle to the ports and for detecting and resolving ambiguities when the number of stations does not equal the number of active ports. The mechanism uses a combination of input and output buffers under control of the programmed hub processor for developing a list of stations connected to the hub. When the number of stations does not equal the number of active hub ports an upstream buffer is configured to transmit Duplicate Address MAC frames to a single port and the contents of a downstream buffer are used to resolve the ambiguity either on a single transmission or multiple single port transmissions.

Port address resolution device

Stations on a faulty token ring which includes a control adapter are removed one at a time starting with the most down stream station from the control adapter or of a station up stream from the last station is known to be good all of the stations down stream from that station are removed and the one at a time removal starts with the known good station. The control adapter transmits special beacon frames during the station removal process and when the removal of a station results in receipt of the special beacon frame at the control adapter, the control program identifies a fault domain which includes the station whose removal caused the special beacon to be received at the control adapter and the station immediately up stream from that station. The stations in the fault domain are selectively subjected tests and removed from the ring when a failure is detected.

Dual ring fault isolation

A multiport access and reconfiguration unit for use in a dual token ring network is provided with three adapters and, depending on error conditions, can assume one of a plurality of recovery states in which a reconfigured single network is formed and at least one state in which an isolated single ring is formed in addition to the reconfigured ring.

Dual ring reconfiguration switching unit

A plurality of access ports in a serial communication network are bracketed by a pair of adapters each of which is connected to a programmed processor. The adapters have unique identities and take part in a polling sequence with any active connected devices each of which have unique network identities. The processor maintains active port status information and correlates the identities of the devices received between the identities of the adapters in a polling sequence to the active port status information which indicates the specific port to which each active device is attached.

Serial network topology and recognfiguration generator

A multiport access and reconfiguration unit for use in a dual token ring network is provided with three adapters which in the presence of an internal fault establishes an isolated token ring which includes one of the adapters and the associated ports, to test and bypass the fault and operate the reconfigured ring with the other two adapters.

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Raleigh, NC, United States of America

Jay L Smith