3com Technologies

Peter A Saunderson

Anne G O'Connell

Vincent Gavin

Dipak M Soni

Donal Casey

Dipak M L Soni

A communication system comprises a plurality of interfaces disposed for sending data packets by way of virtual circuit connections and for receiving data packets by way of virtual circuit connections in an asynchronous transfer mode. The interfaces by means of the virtual circuit connections emulate at least one local area network including unit for establishing a virtual circuit connection functioning as a BUS (broadcast and unknown server) for the broadcast of data packets throughout the emulated local area network. An asynchronous transfer mode switch receives packets by way of virtual circuit connections from each of said the interfaces, replicates the packets and sends them to all the other interfaces, thus to establish a mesh between said interfaces. At least one interface comprises a unit for mapping virtual circuit connections between one interface and at least one terminal which is not directly connectable in the mesh connection into virtual circuit connections in the mesh.

Hybrid distributed broadcast and unknown server for emulated local area networks

An address look-up data-base is used to store medial access control addresses for resolution into channel numbers in a system for transmitting data in an asynchronous transfer mode. Static random access memory is used to contain pointer tables, there being a pointer table for each possible priority level in the data packet. Thus a search for the media access control address of a data packet in the content addressable memory yields, among other data, a priority value which when combined with other data points to a location in one of the pointer tables, which accesses the appropriate channel number.

Method for selecting virtual channels based on address priority in an

Data received in the form of data packets which include destination addresses is transmitted over virtual channels in an asynchronous transfer mode to emulate the operation of a plurality of emulated local area networks. A plurality of bus channels are provided, each specified for the broadcast transmission of data packets to members of a respective one of the emulated local area networks. An address look-up data-base is used to receive the destination address of a data packet and data defining the respective bus channel for the broadcast transmission of that packet in the respective emulated local area network. The data packet is then transmitted over the respective bus channel. The content addressable memory provides a data field which indicates whether a request for the resolution of the destination address into a specific virtual channel number has been made.

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Berkhamsted, United Kingdom

Peter A Saunderson