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Abstract

Methods and apparatus for processing cells in an asynchronous transfer mode (ATM) communication system. A group of bits comprises a primary scoreboard indicative of the scheduling status for cell time slots in a periodic container of cells, with each bit indicating the availability of a corresponding cell time slot. A connection identifier (ID) table is maintained with each location in the table corresponding to one of the cell time slots and thus a single primary scoreboard bit. A cell scheduling instruction specifies a connection ID for a virtual connection on an ATM transmission link. A processor searches the primary scoreboard until a bit corresponding to an available cell time slot is located, reserves the located cell slot by setting the corresponding bit, and stores the connection ID in the corresponding location in the connection ID table. A cell servicing instruction specifies an address in the connection ID table. The processor receives the servicing instruction, retrieves the corresponding primary scoreboard bit, constructs or retrieves a cell for transmission in the slot if the bit was set, and then clears the bit so the slot is available for subsequent scheduling requests. A secondary scoreboard may be used to bound the primary scoreboard search time. The secondary scoreboard includes a bit for each block of primary scoreboard bits. The bit indicates whether the primary scoreboard block includes an available time slot. Portions of the primary scoreboard with no available slots thus need not be searched. Separate tunnel control primary scoreboards may be used in conjunction with a master primary scoreboard to support virtual path tunneling.

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