Patent ID: 6490282
Filing Date: 2002-12-03
Classification: H04L

Abstract:
A switching system for an asynchronous transfer mode switch, comprising:an input interface comprising a switching control cell generator for inserting a switching control cell into an input cell, and a branch circuit for branching a signal with the switching control cell inserted therein into two parts which are then output from the switching control cell generator and are input respectively into an active switch and a stand-by switch, said active switch comprising a cell buffer for accumulating a cell received from the branch circuit, a buffer controller for controlling writing into the cell buffer and reading from the cell buffer, a first active switching control cell detector for detecting a switching control cell from a row of cells received from the branch circuit and notifying the buffer controller of the switch control cell detection, and a second active switching control cell detector for detecting the switching control cell from a row of cells output from the cell buffer and notifying the buffer controller and the stand-by buffer controller of the switching control cell detection, the stand-by switch comprising a cell buffer for accumulating the cell received from the branch circuit, a buffer controller for controlling writing into the cell buffer and reading from the cell buffer, and a stand-by switching control cell detector for detecting the switching control cell from a row of cells received from the branch circuit and notifying the buffer controller of the switch control cell detection; and an output interface having a selecting circuit for selecting the output from any one of the active switch and the stand-by switch, wherein the active buffer controller discriminates a discard priority class of the input cell and controls the write or discard of the input cell according to the number of cells accumulated within the cell buffer and, when the input cell is discarded, notifies the stand-by buffer controller of the discard of the input cell, and, in a period between the receipt of a notification of switching control cell detection from the first active switching control cell detector and the receipt of a notification of switching control cell detection from the second active switching control cell detector, performs, in addition to a discard priority control, a discard control of the corresponding input cell upon a notification of the discard of the input cell from the stand-up buffer control, and the stand-by buffer controller discriminates the discard priority class of the input cell to control the write or discard of the input cell according to the number of cells accumulated within the cell buffer, and, at the time of discard of the input cell, notifies the active buffer controller of the discard of the input cells and, further, in a period between the receipt of a notification of switching control cell detection from the stand-by switching control cell detector and the receipt of a notification of switching control cell detection from the second active switching control cell detector, performs, in addition to the discard priority control, the discard control of the corresponding input cell upon the receipt of a notification of the discard of the input cell from the active buffet control, and, upon the receipt of a notification of switching control cell detection from the stand-by switching control cell detection, discards the input switch control cell and all the cells already accumulated within the stand-by cell buffer to empty the cell buffer, and, further, in this case, until the receipt of a notification of switching control cell detection from the second active switching control cell detector, stops reading of cells from the stand-by cell buffer to equalize the cell accumulated within the active cell buffer to the cell accumulated within the stand-by cell buffer.