| 摘要 |
Methods and apparatus for processing cells in an asynchronous transfer mode (ATM) communication system. An ATM cell processor implements a "bubble" count technique which efficiently accommodates multiple layers of scheduling requests and/or external cell sources. In the case of multiple layers of scheduling requests, first and second primary scoreboards are provided for scheduling/servicing of, for example, higher and lower priority traffic, higher and lower cell rate traffic, or externally and internally generated traffic, respectively. A bubble count is maintained for the second scoreboard, and the count is incremented each time the first scoreboard is serviced and decremented each time an idle slot is encountered on the second scoreboard but not queued for transmission. Scheduling requests for the second scoreboard are then made at a target time plus the bubble count. In the case of multiplexing external and internal cell sources, the bubble count may represent the number of cells that have been sent on a given transmission link but not scheduled in the primary scoreboard, and may be incremented each time the primary scoreboard is serviced, and decremented each time an idle slot on the primary scoreboard is encountered but not queued for transmission. |
