Abstract: A token ring network performs address to port mapping by taking advantage of the abilities of the port switched modules and the neighbor notification process, in order to perform address to port mapping on each individual module. Ring monitors are switched from an upstream side of a port to a downstream side of a port when the neighbor notification process enters the port domain. The processor on the module records all the addresses received on the downstream side of the port, when the neighbor notification process is in the domain of that port. If it appears that the neighbor notification process is in the domain of two adjacent ports, the present invention only records addresses from the most downstream of the two adjacent ports, since such a situation is an indication that the upstream ports do not conform to MAC protocol.

Abstract: Beacon recovery is performed separately on each module. After a module recognizes that a beacon condition has occurred, each module checks to determine if the defect or fault is on its module. If the defect is on the respective module, the module disconnects itself from the remaining modules in the network and transmits a beacon frame onto an upstream end of the group of stations on that module. Each port on the module is then tested to determine if the error lies in the corresponding station. This testing is based on the presence or absence of the beacon frame.

Abstract: A process for testing a wrapped segment of a dual token ring transmits idle signals on the segment and monitors the received signals. If either an Active Monitor, Standby Monitor or Beacon frame is received the process loops. If a Ring Purge frame is received the process exits successfully and the segment is unwrapped. If a timer expires prior to the above, transmission shifts to a Claim Token frame. The process loops if a Beacon frame is received or if one of two timers expires. The process exits and the segment is unwrapped if a Ring purge frame is received or if n Claim Token frames are received having the hub source address.

Abstract: 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.

Abstract: A serial network fault isolation device for use in a network hub has receive and transmit buffers connected to the network. An isolation switch which allows the receive buffer to receive network signals while the transmit buffer sends signals such as media access control (MAC) frames supplied by the hub processor. A decoder connected to the receive buffer recognizes received (MAC) frames and interrupts the hub processor which reads the MAC frame. An idle character generator also under control of the hub processor is used to synchronize the circuit when the hub processor inserts the fault isolation device in the network.

Abstract: 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.

Abstract: 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.

Abstract: A network topology generator identifies addresses and locations of multiple stations connected to a single access port of a communications network by determining a pair of identifiable network units between which the multiple stations are connected, sequentially deactivating access ports between the pairs of identifiable network units and issuing selected message frames to the stations whose location is unknown. The message frames returning from said stations are monitored to detect the state of the Address Recognized (AR) bit. If the bit is set, this indicates that the station is still on the network. Therefore, the deactivate/polling routine is repeated until the AR bit in a returned message is in an "off" state, indicating that the station is not on the network and is connected to the last deactivated port.

Abstract: 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.