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: A data communications system including a network and a number of data communication stations attached to the network wherein each of the stations includes a processor, a memory, a bus, and a communications adaptor for operatively connecting the processor and memory to the network, the communications adaptor including a means for monitoring network activity on a real time basis and enabling or disabling data compression when network activity exceeds a predetermined threshold.

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 network interface card for attaching computers, work stations or the like to a Local Area Network (LAN) includes a device which indicates an address compare if selected bits in a first part of an address, in the address field of a received frame, matches bits stored in the network interface card and at least one bit of a code word stored at a particular address of an index RAM is set to a predetermined state. The particular address in the index RAM is identified by a second part of the address in the received frame. The range of address which can be recognized is further extended by a contents addressable memory (CAM) coupled to the device. The CAM makes a parallel compare between an input address and its contents and outputs a match signal if a match is found. A programmable control register is used to activate or deactivate the CAM or the device.

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: A system (such as a multiprotocol LAN adapter) for use in a workstation or other processing machine automatically determines the type of network to which the workstation is connected and for automatically determines the type of physical medium to which the workstation is attached. The system has a plurality of different physical ports for supporting various available physical media over which network data may be transmitted. For example, the system may have a port for connecting to shielded twisted pair (STP) wiring, a port for connecting to unshielded twisted pair (UTP) wiring, a port for connecting to coaxial cable, and a port for supporting the Attachment Unit Interface (AUI). Connected to each of these physical ports are various network interface devices for supporting the various available networking protocols, e.g., token ring, Ethernet, etc. Logic circuitry and control software are connected to the network interface devices.

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 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.

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 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.