Abstract: A network for transferring information among a plurality of digital devices includes a plurality of switching nodes interconnected by communication links. Each of the digital devices is connected to one of the switching nodes over additional ones of communication links. Each communication link transfers information in a predetermined one of a plurality of types of communications services, with the network including at least one communication link of each service type. The digital devices and switching nodes transfer information through the network over virtual circuits, with each virtual circuit extending from one digital device, as an originating digital device, to another digital device, as a terminating digital device. Each virtual circuit defines a unitary virtual circuit path extending through at least one switching node over a plurality of the communication links without regard to the service type of the ones of the communication links included in the virtual circuit path.

Abstract: Improved methods and apparatus are disclosed for remapping Asynchronous Transfer Mode ("ATM") cells in an ATM switch to convert a single Virtual Path Identifier ("VPI")/Virtual Connection Identifier ("VCI") address pair to multiple outgoing VPI/VCI pairs for multicast transmission. An incoming cell is examined to determine the ports through which the cell will exit and a local header is generated which includes a field specifying the I/O modules ("IOMs") through which the cell will exit. The VPI/VCI pair of an incoming multicast cell is mapped to a global multicast identifier ("MID") which is written into the local header. The cell, including the local header is then forwarded to the IOMs specified in the header. A first lookup table on each IOM is employed to provide a port bitmask indexed by MID to direct the cell to the previously identified ports, and to map the MID into a connection identifier ("CID").

Abstract: A method and apparatus are disclosed for multicasting through a single physical port in a switch, i.e., logical multicasting. An incoming cell is logically multicast by providing a first copy of the cell to the desired output port and providing a second copy of the cell to a loop-back element which includes standard input and output ports dedicated to loop-back operation. The cell provided to the loop-back element is subsequently provided to the desired output port such that the first and second copies of the cell are serially transmitted from the single desired output port. Further, the cell provided to the loop-back element may be repeatedly copied, provided to the loop-back element, and provided to the desired output port. Thus, the incoming cell may be transmitted through a single output port as many times as is desired.

Abstract: Prioritized subclasses of cells within at least one quality of service (QoS) level in an asynchronous transfer mode (ATM) network element are described. Corresponding QoS queues are provided with one or more thresholds for intelligent discard of incoming cells within a QoS, based upon cell priority, at the onset of queue congestion. Cells having a first priority within a QoS are discarded as a first queue threshold is achieved; cells having a higher priority are enqueued. A cell loss priority (CLP) bit is employed to provide a further degree of cell discard prioritization. Different traffic streams within a single queue have different priorities, enabling intelligent discard of lower priority traffic prior to complete queue congestion.

Abstract: A method and apparatus for performing address translation in an ATM network element, such as a switch, resulting in minimized circuit complexity and resultant cost savings. The present invention includes the generation of a simplified local address from elements of internetwork communications, the local address being suitable for addressing a routing table in the network element. Components of the local address are also individually employed as masks for out-of-range checking.

Abstract: Method and apparatus are disclosed for maintaining operational and statistical information in a high speed network switch for each of a plurality of supported connections. A high speed array is provided which includes a plurality of high speed registers for each of a plurality of connections supported by the switch. Upon receipt of a cell/frame, a connection identifier is generated to identify the connection within the network switch and the connection identifier is stored in an index register. The connection identifier stored within the index is used to select a plurality of registers within the high speed register array of registers pertaining to the specified connection. Information pertaining to each received cell/frame is generated upon receipt of the cell or retrieved from the respective cell header and is employed to generate an operand for each of the plurality of registers addressed by the connection identifier.