Abstract: Apparatus and method are provided for enabling unimpeded, clock-to-clock communication between different classes of equipment including converting without queuing of data parallel bytes of digital data having a given number of binary bits to parallel bytes having a different (greater or smaller) number of bits.

Abstract: A pipelined bus which can support more than one channel between data sources and data destinations at a time. The bus includes an arbitration bus, a command bus and a data bus. In accordance with the bus protocol, different channels may access the various bus components in the same clock cycle. For example, the data source of one channel may issue a command on the command bus to its selected data destination to get ready to receive data while at the same time, a data source of a second channel actually transmits data on the data bus to its selected data destination. During the same clock cycle, a third data source can be selected by the arbitration bus to initiate or resume a channel.

Abstract: The bandwidth of a packet data transmission node is switched asynchronously without interruption of data transmission and with a minimum of circuit complexity. In particular, a packet channel is permitted to "breathe", gaining bandwidth when additional bandwidth becomes available from other temporarily unused digital channels and losing such additional bandwidth when such unused digital channels revert to other use. To permit such uninterrupted asynchronous operation, a "pad" or "throw away" character is defined which is ignored or discarded when it is received by another packet network node. Such a "pad" or "throwaway" character is unique only in the sense that it is distinct from and may not be confused with characters or bytes which may occur in normal data transmission sequences.

Abstract: A hub for a segmented virtual local area network with shared media access has at least one internal port for receiving and transmitting digital data messages within the hub and may have at least one external port for receiving and transmitting digital data messages external to the hub. The hub further includes a memory for storing virtual local area network (VLAN) designations for internal and external ports. The hub associates VLAN designations with at least one internal port, stores such VLAN designations in the memory, and associates the stored VLAN designations with messages transmitted from any of the ports to which the VLAN designation has been assigned. Additionally, the hub identifies VLAN designations associated with messages received by or within the hub and means and transmits to any of the internal ports only messages received within the hub and having associated with them a VLAN designation which matches the stored VLAN designation assigned to the port.

Abstract: A distributed digital communications network has an originating node and a multiplicity of destination nodes. The various nodes are interconnected by links and at least some of the nodes are accessible to other nodes only by multiple links. To save time in establishing the least cost path from an originating node to a destination node, the attributes of the various links are stored in memory at the originating node, a least cost path from the originating node to a destination node is calculated in response to a connection request and stored in memory. Then, when a subsequent connection request to any destination node requires the same link attributes as the least cost path already stored in memory, that same least cost path is used if it is still operational. Significant time saving is achieved in that no new least cost calculation need be made.