3com Corporation

3com Technologies

Nicholas Mark Stapleton

David J Law

Christopher Alan Walker

Tadhg Creedon

Michael Sean McCormack

Vincent Gavin

Justin A Drummond-Murray

Una Quinlan

Paul Francis Dryer

Patrick Michael Overs

Denise De Paor

Edward Turner

Peter J Wilson

Nigel Horspool

Christopher Byham

Steven Brewer

David R Smith

Pauric O'Callaghan

David Wright

A stackable network unit which can form a ring with other units has a master mode in which it can place packets on the ring, so that they can be ultimately forwarded from other units, and a repeat mode in which it can make a request for transfer of mastership of the ring, inserting bits in a header of an arbitration packet. If a master unit has completed the transmission of a packet and, preferably, after the required inter-packet gap has elapsed, it has not yet received an arbitration header to permit the making of an arbitration decision it can transmit a subsequent packet. The header information of this packet indicates to the other units that this subsequent packet is part of a burst of packets and the other units should not set requests in the header of this packet because this packet would not be used for arbitration. The master unit indicates the nature of the subsequent packet by setting a sequence number in the header of the packet to distinguish it and following packets in a burst from the 'first' packet which is the one used to pick up requests from the units that may need to become the master unit.

Stackable ring network including burst transmission of data packet

A stackable network unit comprises a 'down' port and an 'up' port, an arbitration path for data packets from the down port to the up port, a repeat path for data packets from the up port to the down port, a link detector for detecting tile absence of another operative unit connected to the down port to cause data packets on the return pat to bypass the down port and proceed on the arbitration path and for detecting the absence of another operative unit connected to the up port to cause data packets on the arbitration path to bypass the up port and proceed on the repeat path.

Method and apparatus for configuration of stackable units in packet-based communications systems

According to the invention, an Ethernet system and method of using an Ethernet system is provided including a network side device (a hub/switch/concentrator), and a plurality of end devices (either a standard end device powered locally or a system powered device), connected to the hub/switch. The system powered devices have circuitry for indicating the system power need to the hub, which has a power source for selectively supplying system power over the Ethernet. A stimulus device associated with the network device sends a stimulus signal over the network connection lines during a detection phase. The need for power is signaled by an indication device associated with the system powered end devices, providing an indication signal in response to the stimulus signal. A detector associated with the network side detects the indication signal thus triggering the power source to supply system power to each of the end devices that is a system powered device and not to each of the end devices that is a standard device.

System and method for signaling and detecting request for power over ethernet

A communications apparatus comprising a plurality of communication devices each having a plurality of ports and a data bus interconnecting the plurality of units, wherein each device is provided with means enabling the device to detect automatically its position on the data bus.

Communication device with circuitry to promote cascade series connection including identification of device position in the series and sensing the end device in the series

A data network hub unit is stackable with other such units to constitute a hub in which each of the units can supply data packets to network data destinations and receive data packets from network data sources, and to form a closed data transmission ring which enables packets received at any unit to be transmitted from any other unit. The hub unit includes arbitration control means responsive to packet headers circulating on said ring. The arbitration control means is operative: (i) when the hub unit acts a master unit to supply data packets, to modify data packets to provide them each with an arbitration header which includes a grant field, a request priority field, capable of indicating various different level of priority, and a grant priority field; (ii) when the hub unit is acting as the master unit and has no more data packets to supply to the ring, to respond to an arbitration header which has a set priority field by setting the grant field and setting the grant priority field; (iii) when the hub unit is not the master unit but has data packets to place on the ring, to respond to arbitration headers by setting a priority field; and (iv) when the hub unit is not the master unit but has data packets to send, to respond to an arbitration header which has the grant field set and a grant priority field indicating a priority level corresponding to the priority requested by this unit to become the master unit.

Hub system with ring arbitration

The occurrence of collision and activity in a computer network is indicated by activation of a visual indication device. The device is activated for periods which are longer than the actual periods of collision and activity to permit the human eye to register the visual indications. This is particularly useful for high speed networks where the periods of collision and activity may be very brief.

Network hub activity display

A repeater for a computer network, and a network incorporating such a repeater are described in which repeater communication addressed to a subset of the devices connected to the repeater are transmitted in a corrupt or scrambled form to other network devices. The processing load is thus reduced for such other network devices, in particular in the context of high volume multicast traffic such as in video conferencing.

Multicast filtering

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Uxbridge, United Kingdom

Nicholas Mark Stapleton