Bay Networks, Inc.

Synoptics Communications, Inc.

Bay Networks Group, Inc.

Paul Woodruff

Geoffrey O Thompson

Michael J Armstrong

Vasmi Abidi

A method and apparatus for a node to automatically switch between half-duplex and full-duplex transmission in CSMA/CD networks characterized by a first and second device coupled over a communication link to allow communication of information and control signals between the first and second device. Each of the two devices include a transmit circuit and a receive circuit, wherein the first device begins to transmit information on a first communication circuit, the first communication circuit providing for communication of information between the first device and the second device, and the second device receives the transmitted information. If, while the first device is transmitting information to the second device, the second device begins to transmit information on a second communication circuit, the second communication circuit providing for communication of information between the second device and the first device, and the first device receives the transmitted information, full-duplex communication therebetween is established. If, while the first device is transmitting information to the second device, the second device transmits a collision detect signal and the first device receives the collision detect signal, half-duplex communication therebetween is subsequently established.

Method and apparatus for switching between full-duplex and half-duplex

A multi-segment agent topology mechanism for use by multi-segment network devices in an Ethernet network. Topology information packets exchanged between topology agents in a network include segment identifier information as well as IP address of the sending agent. A device's topology agent maintains and updates topology information in topology tables which identifies interconnected network devices, such as concentrators and bridges, by IP address and segment identifier information as well as incoming slot and port information for eventual use by a network management system in evaluating a networks topology map, and in automatically determining changes in the network's topology.

Method and apparatus for determining and maintaining agent topology

A concentrator having a single medium access controller for monitoring a plurality of communication lines is provided. Each of the communication lines corresponds to a network and carries identification signals periodically transmitted by devices on the corresponding network. The medium access controller includes a transmit unit and a receive unit. The transmit unit sequentially broadcasts concentrator identification signals over each of the communication lines. The transmit unit sequences through the communication lines at a rate to insure that a concentrator identification signal is sent over each communication line during a predetermined transmit interval. The receive unit sequentially monitors the signals on each of the communication lines. The receive unit monitors the signals on any given communication line for a predetermined monitoring period before sequencing to the next communication line. The duration of the monitoring period for a given communication line is at least as long as the longest identification signal transmit interval for any device on the communication line. Consequently, the receive unit will detect an identification signal from all of the active devices on a given communication line during the monitoring period for the communication line. The receive unit stores an indication of the identification signals it detects and the ports on which they were detected. This stored information may be used by a network management station to generate a map showing how the concentrator is connected to other devices.

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Sunnyvale, CA, United States of America

Paul Woodruff