Abstract: This invention relates to the merging of data cells arriving at an Asynchronous Transfer Mode (ATM) switching node from data frames originating with a number of senders. As is standard in ATM networks, each originating frame is segmented into a series of cells each having Virtual Path Identifier (VPI) and a Virtual Channel Identifier (VCI) in its header portion. On arrival at each switching node, the VCI of the first cell of a frame is overwritten by a new outgoing VCI value that is used for all other cells of the frame. Thus, the actual movement of each cell through the network is controlled only by the cell's VPI, whereas the VCI field is used only to distinguish frames from each other. A feature of the invention is that it can accommodate Early Packet Discard in a simple way by associated any discard indication determined for a frame with the outgoing VCI value which also applies to all cells of the entire frame.

Abstract: The present invention is an apparatus that manages Packet-Discard at a switch in an ATM network. The apparatus includes a table having a number of table addresses (or indexes). Each table address stores a record for incoming data cells of a frame. The records indicate whether data cells of the frame are be discarded. The number of possible cell identifiers is greater than the number of table addresses. The apparatus also includes a processor unit which receives a data cell having a cell identifier. The processor unit determines a table key, based on the cell identifier such that the table key is within the range of the table addresses. The processor unit then searches a record in the table associated with the table key to determine whether the data cell is to be discarded.