3com Corporation

Hewlett-packard Development Company, L.p.

Quang T Tran

David J Law

Paul J Moran

Alan R Poulter

Sharon L Wiles

Eugene O'Neill

Edele O'Malley

Kam Choi

Jerome Nolan

Bryan J Donoghue

Maurice A Goodfellow

Christopher Alan Walker

Richard N Bayfield

David Whitfield

Patrick Michael Overs

Nigel Horspool

Maunte A Goodfellow

In one embodiment, a method is described for detecting an operational failure between the network unit and an adjacent network unit in the stack; controlling the switching engine to redirect packets which would otherwise be sent from a particular port to the adjacent network unit to be forwarded from another port to be sent to a different network unit in the stack; and entering the switching engine into a bypass mode in response to control data indicating an operational failure between at least two other network units in the stack to cause packets to be forwarded without being re-directed by the switching engine.

Cascade system for network units

A network stack includes a plurality of network units each of which includes a multiplicity of ports for receiving and forwarding addressed data packets, at least two cascade ports and a switching engine for forwarding received packets to at least one port in accordance with address data in the packets and a cascade connection including, for each of two opposite directions around the stack, at least one unidirectional path for data packets composed of links each between a respective cascade port on a network unit and a corresponding cascade port on the next network unit.

Network units such as switches for use in a cascaded stack are organised to provide a cascade connection in the form of a dual unidirectional connection so that, in its ordinary configuration, there is at least one and preferably more than one unidirectional ring for each direction around the cascade, each ring including a respective port on each unit. For each ring, each port on a unit is connected by a respective link to a corresponding port on the preceding unit and the following unit. The units provide a self-healing operation in the event of various kinds of operational failure. The self-healing operation includes loop-back of packets in units adjacent the failure and bypass of a packet switching process for other units. The units include control logic for passing control frames containing status information relating to the units and links between them and for co-operation with a CPU to control a switching engine to perform the self-healing operation in accordance with that status information. The units forward on the cascade packets with headers that identify a destination port and the unit on which that port is located and also indicate which units have and have not been traversed by a packet.

A connecting unit for use in a system comprising a 'stack' of network communication units having a cascade connection has three ports having lines for forwarding and receiving data packets and for forwarding and receiving control messages. The connecting unit increments a first signal value defining an identification number received by way of a control message at a first port, provides the received signal value by way of a control message to the third port and provides the incremented signal value by way of a control message to the second port. The connecting unit also receives a second signal value defining an active unit count by way of a control message at the first port and provides the second signal value, incremented or not in dependence on a control message received at the third port, in a control message at the second port. The first signal values (UnitIDs) are used to establish the numbering of the units in the stack and the second signal values are used to compute a count of the 'active' units in the stack.

Cascade architecture and operation for packet-based communication systems

A control device for a unit in a cascade connection of network units includes control logic which increments a count of active units and passes the count to the next control device. The count is initiated and terminated by an absence of control messages at the down port and up port respectively. The incremented count is passed up the cascade and a final count is passed down the cascade.

Cascade control architecture and operation for packet-based communication systems

A network communications device is arranged to have a fast throughput of data packets. This is achieved by recognising that, in protocols such as Ethernet, the first symbols in a data packet do not carry any data and therefore do not necessarily require to be properly carried through a communications hub. Rather, a known number of symbols are discarded from the start of a packet on receipt and replaced on re-transmission. This discarding reduces the reception delays particularly in bussed-architecture repeaters where bus arbitration must take place for each received packet.

Network communication device

Housing of an electronic extender

An extender for use in with a cascade stack of network devices comprises an electronic circuit which has three ports, and circuit connections coupling each of the three ports to each of the other two ports; port connectors for each port; a two-part housing of which a first part has an end wall apertured for the protrusion of a first and a second of the connectors and a second part has an end wall apertured for the protrusion of a third of the port connectors; and screw fixings for securing the housing parts together.

Growing community of inventors

Wokingham, United Kingdom

Quang T Tran