Hitachi, Ltd.

Atsuo Hatono

Masashi Hiraiwa

Shinichi Hamamoto

Tatsuya Watanuki

Atsushi Kimoto

Tatsuo Mochinaga

Tadashi Tamaoki

A regulation apparatus for ATM cell delay variation includes a variation regulating buffer for temporarily storing cells transferred thereto, a variation waiting timer for controlling a waiting time which extends from reception of the first cell to read-out of cells from the buffer, a read-out timer for controlling intervals at which cells are read from the buffer, a latest cell preservation memory for storing the latest cell transferred from a VPI/VCI demultiplexing unit and, a selector for selecting a cell stored in the buffer or in the memory to transfer the selected cell to a cell reproduction unit. The invention further includes a communication type discriminator for discriminating a communication type in a call set-up phase upon starting a communication and for calculating a variation waiting time in accordance with the discriminated communication type to set the calculated variation waiting time to the variation waiting timer, and a dummy cell inserting circuit for inserting the last reaching cell as a dummy cell if a cell delay time cannot be regulated by the variation waiting time in a communication of sound or moving images.

Regulation method and apparatus for ATM cell delay variation

A cell loss priority control method for an ATM switch in which degradation of the traffic characteristics of a high priority class or a low priority class is detected, a cell loss probability distribution in a buffer is estimated from the cell traffic characteristics, a buffer threshold value is obtained in accordance with the estimated cell loss probability distribution, and the cell is controlled by using the obtained buffer threshold value which maximizes total traffic throughput of both the high priority class and low priority class.

Cell loss priority control method for ATM switch and ATM switch

An ATM exchange for performing the flow control adaptively in accordance with the seriousness of congestion, provided with a first threshold comparing circuit and a second threshold comparing circuit for comparing a cell queue length in a buffer of the exchange with a first and a second threshold, a timer counter which starts counting when the queue length exceeds the first threshold and is cleared to zero when the the queue length becomes smaller than the second threshold, a permissible time comparing circuit for comparing the count value with a permissible time, and a congestion counter for counting the output of the comparing circuit. The ATM exchange sets the first threshold, second threshold, and permissible time from the number of multiplexings of standard traffic, mean cell rate, peak cell rate, mean survival time of burst length, and false alarm probability, and judges that the heavy congestion is occurring when the queue length does not return to the second threshold or lower within the permissible time, and controls the flow of traffic, and at the same time, when this state continues, the flow restriction is enhanced depending on the elapsed time from the permissible time.

ATM exchange performing traffic flow control

A regulation apparatus for ATM cell delay variation includes a variation regulating buffer for temporarily storing cells transferred thereto, a variation waiting timer for controlling a waiting time which extends from reception of the first cell to read-out of cells from the buffer, a read-out timer for controlling intervals at which cells are read from the buffer, a latest cell preservation memory for storing the latest cell transferred from a VPI/VCI demultiplexing unit and, a selector for selecting a cell stored in the buffer or in the memory to transfer the selected cell to a cell reproduction unit. The invention further includes, a communication type discriminator for discriminating a communication type in a call set-up phase upon starting a communication and for calculating a variation waiting time in accordance with the discriminated communication type to set the calculated variation waiting time to the variation waiting timer, and a dummy cell inserting circuit for inserting the last reaching cell as a dummy cell if a cell delay time cannot be regulated by the variation waiting time in a communication of sound or moving images.

An ATM switch system having a traffic control function to reduce cell loss probability and delay of cells communicated through a network to be equal to or less than acceptable values, respectively. To achieve traffic control function, the invention provides a circuit to observe the queue of cells in the buffer, and an overflow testing circuit for obtaining a distribution of the queue size according to observed values of the queue and testing to decide, according to the distribution, whether an event has occurred that the cell loss probability is shifted due to the input cells to a distribution related to a cell loss probability exceeding an upper-limit value of acceptable cell loss probability. The invention also provides an underflow testing circuit for testing, according to the distribution, whether an event has occurred that the cell loss probability is shifted to a distribution related to a cell loss probability less than a lower-limit value of acceptable cell loss probability such that the read delay and interval of input cells are altered according to outputs from the overflow and underflow testing circuits.

ATM exchange, ATM multiplexer and network trunk apparatus

An ATM network includes a plurality of ATM-LANs which are connected through an ATM-WAN, when a source terminal and a destination terminal belong tb separate ATM-LANs connected through the ATM-WAN, the congestion control is performed as follows. When congestion occurs in an ATM-LAN in which the source terminal exists, the congestion control is performed by the BECN mechanism and when congestion occurs in an ATM-LAN other than the ATM-LAN in which the source terminal exists, the congestion control is performed by the FRP mechanism. When the source terminal and the destination terminal exist in the same ATM-LAN, the congestion control is performed by the FECN mechanism. Thus, in the ATM-LAN, cell loss can be suppressed upon occurrence of congestion.

Growing community of inventors

Yokohama, Japan

Atsuo Hatono