Fujitsu Corporation

At+t Corp.

Hitoshi Uematsu

Hiromi Ueda

Takao Ogura

Yasuki Fujii

Shigeo Amemiya

Koji Tezuka

Mark A Pashan

Yuichi Matsuda

Shahrukh S Merchant

An alarm masking system is provided which is capable of implementing alarm priority processing or alarm inhibit processing in ATM transmission equipment. In ATM transmission equipment, a received virtual path or virtual channel is switched by means of a switching unit and then sent to an interface unit. In doing this, if a higher priority alarm is detected or received at a reception side interface unit, an intra-office tag is added to the alarm cell and then it is output, so that by detecting this intra-office tag it is possible to inhibit generation of lower priority alarms in response to the higher order alarm.

System for achieving alarm masking processing

In a duplicate active-standby memory unit arrangement, a resynchronization initiation determination is made on a cell-interval-by-cell-interval basis based on the equality of cell contents of corresponding queues in the active and standby memory units. If an inequality of the cell contents of the corresponding queues in the active and standby memory units occurs during any cell interval, resynchronization may be initiated. In an exemplary embodiment of the invention, the lengths of data in corresponding queues, i.e., the number of cells stored in the corresponding queues, in the active and standby memory units are compared on a cell-interval-by-cell-interval basis. If the number of cells stored in any of the queues is different than the number of cells its corresponding queue in the other of the memory units during any cell interval, resynchronization of the memory units is initiated. In another embodiment of the invention, the outputs of corresponding queues in the active memory unit and the standby memory unit are compared on a cell-interval-by-cell-interval basis. If the results of the comparison indicates that any one or more of the queue outputs in one of the memory units is different from the output of the corresponding queue in the other memory unit, resynchronization is initiated. Robustness of the latter comparison algorithm is enchanced by restricting the comparisons to cell intervals during which the queue outputs in the active and standby memory units do not both include idle cells. Additionally, robustness of the resynchronization initiation is further enhanced by simultaneously employing both the comparison of cell length in the queues and the comparison of the queue output contents to detect when to initiate resynchronization.

Resynchronization of asynchronous transfer mode (ATM) switch fabric

Growing community of inventors

Yokosuka, Japan

Hitoshi Uematsu