Method of supporting unknown addresses in an interface for data transmission in an asynchronous transfer mode

A method of transmitting over virtual channels in an asynchronous transfer mode data received in the form of data packets which include destination addresses and for emulating the operation of a plurality of emulated local area networks, the method comprising the steps of:

• defining a plurality of BUS channels each specified for the [for the] broadcast transmission of data packets to all the members of a respective one of said emulated local area networks;
• causing a memory to receive the destination address of a data packet and data defining the respective BUS channel for the broadcast transmission of said packet in the respective emulated local area network;
• transmitting the said data packet over said respective BUS channel;
• and
• providing in said memory a data field which indicates whether a request for the resolution of said destination address into a specific virtual channel number has been made.

An interface for receiving data packets including media access control destination addresses and for transmitting said data packets over virtual channels in an asynchronous transfer mode within a plurality of emulated local area networks, the interface including:

• memory means for defining specific virtual channels for the transmission of data packets to members of said emulated local area networks, said members corresponding to said media access control destination addresses, and, for each of said emulated local area networks, defining a respective virtual BUS channel for the broadcast transmission of data packets to all the members of the respective emulated local area network;
• an address look-up database receiving medial access control destination addresses of data packets and for storing media access control destination addresses and associated data identifying in cooperation with said memory means at least one specific virtual channel for the transmission of packets containing a respective media access control destination address, said address look-up database including a data field for an indication that a request for the resolution of a media access control destination address with a specific virtual channel number has been made, and means operative when said look-up database receives a new media access control destination address to write said indication into said data field and to cause packets having the said new media access control destination address to be sent to a respective BUS channel.